podcast Peter Attia 2022-03-07 topics

#198 - Eye health—everything you need to know | Steven Dell, M.D.

Audio

Show notes

Steven Dell is an ophthalmologist, current Medical Director of Dell Laser Consultants, and a leader in refractive eye surgery with over 20 patents to his name. In this episode, Steven explains the anatomy and functional mechanics of the eye and how they relate to common variations in vision. He discusses changes in vision that occur with aging, the fundamentals of different types of vision loss, and provides an in-depth look into the various treatments and procedures available for corrective eye surgery. Additionally, Steven explains how one might protect the eyes and prevent vision loss—a topic particularly important for children in light of the epidemic of myopia.

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We discuss:

Why Steven chose ophthalmology, and the crossovers to other medical disciplines [3:45];
Anatomy of the eye, common types of vision loss, and age-related vision changes [14:15];
Eye drops that can potentially improve vision [27:30];
The explanation for different eye colors [33:15];
Physiology of the eye and its connections to the brain [34:45];
Understanding human vision through an evolutionary lens [41:00];
Enhancing vision beyond 20/20 [47:00];
Astigmatism: definition, cause, and high prevalence [51:30];
Nearsightedness (myopia): causes, epidemic in children, and prevention strategies [54:15];
Cataracts: impact of aging and how they can be repaired [1:05:00];
Lens implants that can correct and improve vision [1:19:30];
Effects of eye trauma [1:26:45];
Corneal abrasion from ‘dry eye’: causes, treatment, and prevention strategies [1:29:00];
Sunglasses for eye protection [1:35:00];
Solutions to correct nearsightedness [1:42:00];
Laser eye surgery—photorefractive keratectomy (PRK) [1:45:45];
Laser eye surgery—LASIK [2:02:00];
Laser eye surgery—small incision lenticule extraction (SMILE) [2:11:45];
Glaucoma: definition, causes, symptoms, and care [2:13:45];
Tips for preserving eye health [2:20:00];
Screen time and eye health [2:24:15];
Contact lenses: good hygiene and considerations [2:27:45];
A bonus benefit from repairing cataracts [2:29:00];
Questions about corrective eye surgery [2:31:30];
How an eye exam can be a window into metabolic illness [2:33:45]; and
More.

Show Notes

*Notes from intro :

Steven is an internationally recognized leader in refractive eye surgery, specializing in LASIK surgery, cataract surgery, and refractive lens exchange
He’s also the chief medical editor of the Cataract & Refractive Surgery Today
He’s the Emeritus Chair and President Emeritus of the American European Congress of Ophthalmologic Surgery
He’s a principal investigator on a variety of FDA clinical trials in the field of eye surgery
He’s the inventor of several surgical instruments and devices and holds over 20 US and international patents in the field of eye surgery
He is also the author of numerous textbook chapters and peer-reviewed journal articles
Peter notes, “ In this episode, we talk about all things related to the eye, and I’m pretty open in the outside of this in explaining that of all the things that one would learn in medical school there are none that I know less about than the eye. In fact, I come into this episode truly knowing as little as a layperson would know about the eye, and I think at the outside of the interview, I explain the extent to what I know about the eye. While it may be slightly more than you will know, I promise you that within about 15 minutes of this episode we are all going to be at the same level. ”
Peter found this discussion fascinating; he treated it almost like the discussion he would have with Steven if they were at a cocktail party He really picks Steven’s brain about the anatomy of the eye Why is this relevant? How does it factor into the natural processes of aging? How does that differ from some of the pathologic processes that also tend to increase with age, but are not necessarily related to aging, per se.?
This episode gets into the really simple fundamentals— what is nearsightedness? What is farsightedness? What is presbyopia, which by the way Peter used to think was farsightedness till he did this interview
Also discussed are what the treatments look like for these things Including a very nuanced discussion about how the different treatments might be beneficial to some people versus others
LASIK eye surgery will be explained as well as a procedure that came along slightly before that’s called PRK
Steven will talk a little bit about a procedure that is coming online today, called SMILE
All three of these surgeries are similar, but they differ in fundamental ways, and that can be an important thing to consider for someone in the market for one of these procedures
Eye health is also discussed What are the things that one can do? What can be done to maximize eye health in our kids?
Also discussed are some of the real epidemics that are going on in myopia That is to say, kids that are requiring glasses earlier and earlier What could be the cause of this and what can be done in our kids to prevent those things, and also in ourselves, what we can be doing A lot of stuff is covered in this episode
He really picks Steven’s brain about the anatomy of the eye
Why is this relevant?
How does it factor into the natural processes of aging?
How does that differ from some of the pathologic processes that also tend to increase with age, but are not necessarily related to aging, per se.?
What is farsightedness?
What is presbyopia, which by the way Peter used to think was farsightedness till he did this interview
Including a very nuanced discussion about how the different treatments might be beneficial to some people versus others
What are the things that one can do?
What can be done to maximize eye health in our kids?
That is to say, kids that are requiring glasses earlier and earlier
What could be the cause of this and what can be done in our kids to prevent those things, and also in ourselves, what we can be doing
A lot of stuff is covered in this episode

“ This is really the everything you need to know about the eye episode ” – Peter Attia

Why Steven chose ophthalmology, and the crossovers to other medical disciplines [3:45]

The eye is a topic that everybody has questions on, Peter included
From medical school, Peter remembers there is an optic nerve , a cranial nerve , and the second cranial nerve (this is the optic nerve) He remembers something called fovea , and he knows there’s a blind spot, but he’s forgotten why
Peter remarks, “ It’s safe to say my knowledge of this topic right now is probably at par with everybody’s right? ”
Steven understands, “ Well, that’s not rare, frankly, because the eye is so literally compartmentalized. We just don’t interact that much with other specialties, so it’s not rare for people who are in other specialties to be very ignorant of the eyeball, and that’s fine because I think it’ll help us keep the level of discussion at an approachable level for everyone. ”
Peter asks if there has ever been discussion suggesting that ophthalmologists don’t need to do the four-year MD degree How much of what was learned in medical school became relevant in residency?
Steven says there was quite a lot There’s nothing specifically magical about the eyeball It’s got neurological tissue in the back, actual brain tissue in the back It’s got a vascular supply There are a lot of crossovers to other medical disciplines All of the cellular processes are the same He operates adjacent to the eye
He thinks it’s important for ophthalmologists to have a general sense of medical knowledge, particularly because so many systemic diseases manifest as eye problems
Now there is a discipline of medical training or of visual training, basically optometry — which deals with the eye, but not all of the surgical stuff
He works in a collaborative fashion with optometrists Those are the folks who are fitting glasses They’re screening for eye disease They’re handling preoperative and postoperative care in many cases They’re treating some diseases that are specific to the eye, such as glaucoma
He remembers something called fovea , and he knows there’s a blind spot, but he’s forgotten why
How much of what was learned in medical school became relevant in residency?
There’s nothing specifically magical about the eyeball
It’s got neurological tissue in the back, actual brain tissue in the back
It’s got a vascular supply
There are a lot of crossovers to other medical disciplines
All of the cellular processes are the same
He operates adjacent to the eye
Those are the folks who are fitting glasses
They’re screening for eye disease
They’re handling preoperative and postoperative care in many cases
They’re treating some diseases that are specific to the eye, such as glaucoma

Ophthalmology training

Peter asks about ophthalmology residency— does everyone spend time operating? Is there a nonsurgical discipline to this? Does the training bifurcate?
Steven explains, “ There are nonsurgical ophthalmologists, but I think they all start out as surgeons to become an ophthalmologist. You’re really training to become an eye surgeon. ” But there are, for example, neuro-ophthalmologists, which are really more neurologists than eye surgeons; they don’t do eye surgery There are some ophthalmologists who don’t do eye surgery
Peter recalls one of his lasting memories from residency was stealing suture from the ophthalmology OR at Hopkins As the number of the suture gets larger the suture itself gets smaller An O suture is thick, like a piece of rope The scale progresses from 1-0, 2-0, 3-0, etc By a 4-0 suture, it’s actually quite thin
Steven replies they use an 11-0 suture
Cardiac surgery uses a 7-0 Occasionally there’s some guys that would sew the distal end of a coronary artery with an 8-0 and at that level, it’s already very thin; just the slightest tug too much, and it breaks
Peter recalls about ophthalmology, “ you guys wrote 11-0, and so I used to steal 11-0 constantly every night I was on call and practice suturing with 11-0. The thinking being, if you can tie in 11-0 with your hands and not tear it, that 7-0, which normally is like a piece of hair is going to feel like a piece of rope. I used it to help me develop a good feel for fine suture ”
The tools in ophthalmology are tiny and Steven can remember the operating room where he did his training was near orthopedic surgery
Is there a nonsurgical discipline to this?
Does the training bifurcate?
But there are, for example, neuro-ophthalmologists, which are really more neurologists than eye surgeons; they don’t do eye surgery
There are some ophthalmologists who don’t do eye surgery
As the number of the suture gets larger the suture itself gets smaller
An O suture is thick, like a piece of rope
The scale progresses from 1-0, 2-0, 3-0, etc
By a 4-0 suture, it’s actually quite thin
Occasionally there’s some guys that would sew the distal end of a coronary artery with an 8-0 and at that level, it’s already very thin; just the slightest tug too much, and it breaks

“ You hear this Black and Decker stuff going on over there, and our little tiny tools are very, it’s just totally different ” – Steven Dell

Everything he does operationally is under a microscope They use a binocular microscope So he’s looking through both eyes, and this is either mounted from the ceiling and is controlled by his feet The X, Y, and Z, and the zoom focus are controlled by a foot pedal And that either comes from the ceiling or it’s on a really large stand
He’s sitting and looking straight ahead, so the image is here, but he operating down below It’s interesting because sometimes his wife will kid him, I’ll come home from a day of surgery exhausted, but she says something like, “ well, I don’t really get it. You’re just sitting in a chair, making these little tiny movements, and there’s soft music playing. It all seems very, very sedate. ” It’s incredibly stressful and exhausting
Ophthalmologists have a problem where they tend to hyperextend They tend to bring their head forward, to come up to the oculars and that creates a whole other set of problems There are ergonomic challenges for sure, and he remembers early on in his career, he was coached very carefully on how to sit, how to have his spine arranged One doesn’t want to crane their neck forward He has to make sure his shoulders are down Steven notes, “ It’s interesting because when you train surgeons, and you look at them, they’re all raising their shoulders up, and they’re terrified that they’re going to do something wrong. They’re in a very, very compromised and stressful position, and then they tend to lift their hands up. ” The surgical movements are these little tiny movements, so very small positional changes can have a huge impact on the outcome of the surgery
Peter understands this problem, he has 2 friends from residency who required multiple neck surgeries One of them could no longer operate after his surgery; he trained as a cardiac surgeon and now does cardiac critical care It’s still a great career, but after 10 years of training as a cardiac surgeon, to not be able to operate…
Peter asks if Steven knew he wanted to do ophthalmology when he began medical school
No, but he knew he wanted to do something surgical, something with his hands
He remember a Eureka moment where the first time he looked through a slit lamp (which is basically a microscope to look into the eye) he was hooked This was during an ophthalmology rotation in a weeks where they did a little ophthalmology and a little ear, nose, and throat It was then that he knew ophthalmology was what he wanted to do He had some exposure to ophthalmology prior because the father of one of his friends was an ophthalmologist
Peter asks if ophthalmologists do a general surgery internship
Some do; Steven did what is referred to as a transitional residence internship, where one does a little bit of everything: general surgery, internal medicine It was very helpful The general surgery part was rough, but it was nice to have exposure to a little bit of everything
It was a 4-year residency, including the internship
Peter asks what was the “bread and butter”? For example, in general surgery in the 1960’s and 1970’s, it would’ve been Billroth procedures and things like that, where the most common thing one was doing was cutting out half of the stomach because of peptic ulcer disease and things like that By the time he got to residency, he never did one of those because H2 blockers and PPIs basically eliminated the need to surgically remove part of the stomach for gastric or peptic ulcers
Peter wants to know, at the time of his training, where did 80% of the volume come from? What type of cases?
It was cataract surgery and then retinal disease It’s still cataracts The scourge of essentially diabetes causes these very, very complex retinal problems
They use a binocular microscope
So he’s looking through both eyes, and this is either mounted from the ceiling and is controlled by his feet The X, Y, and Z, and the zoom focus are controlled by a foot pedal And that either comes from the ceiling or it’s on a really large stand
The X, Y, and Z, and the zoom focus are controlled by a foot pedal
And that either comes from the ceiling or it’s on a really large stand
It’s interesting because sometimes his wife will kid him, I’ll come home from a day of surgery exhausted, but she says something like, “ well, I don’t really get it. You’re just sitting in a chair, making these little tiny movements, and there’s soft music playing. It all seems very, very sedate. ”
It’s incredibly stressful and exhausting
They tend to bring their head forward, to come up to the oculars and that creates a whole other set of problems
There are ergonomic challenges for sure, and he remembers early on in his career, he was coached very carefully on how to sit, how to have his spine arranged One doesn’t want to crane their neck forward He has to make sure his shoulders are down
Steven notes, “ It’s interesting because when you train surgeons, and you look at them, they’re all raising their shoulders up, and they’re terrified that they’re going to do something wrong. They’re in a very, very compromised and stressful position, and then they tend to lift their hands up. ”
The surgical movements are these little tiny movements, so very small positional changes can have a huge impact on the outcome of the surgery
One doesn’t want to crane their neck forward
He has to make sure his shoulders are down
One of them could no longer operate after his surgery; he trained as a cardiac surgeon and now does cardiac critical care It’s still a great career, but after 10 years of training as a cardiac surgeon, to not be able to operate…
It’s still a great career, but after 10 years of training as a cardiac surgeon, to not be able to operate…
This was during an ophthalmology rotation in a weeks where they did a little ophthalmology and a little ear, nose, and throat
It was then that he knew ophthalmology was what he wanted to do
He had some exposure to ophthalmology prior because the father of one of his friends was an ophthalmologist
It was very helpful
The general surgery part was rough, but it was nice to have exposure to a little bit of everything
For example, in general surgery in the 1960’s and 1970’s, it would’ve been Billroth procedures and things like that, where the most common thing one was doing was cutting out half of the stomach because of peptic ulcer disease and things like that
By the time he got to residency, he never did one of those because H2 blockers and PPIs basically eliminated the need to surgically remove part of the stomach for gastric or peptic ulcers
It’s still cataracts
The scourge of essentially diabetes causes these very, very complex retinal problems

Anatomy of the eye, common types of vision loss, and age-related vision changes [14:15]

When Steven explains the eye to a kid, he compared it to a camera with film in the back; that’s the retina Then the kid looks at his parents and asks, “ What’s a camera? Film, what’s that? ”
The eye is built like a camera where in the very front is the cornea The cornea is the covering on the front of a watch; that’s the thing that a contact lens would sit on
Then the kid looks at his parents and asks, “ What’s a camera? Film, what’s that? ”
The cornea is the covering on the front of a watch; that’s the thing that a contact lens would sit on

Figure 1. Anatomy of the eye. Image credit: Kellogg Eye Center

The next thing is the pupil , which is the hole in the iris
Behind that is the lens , it’s really one of a couple of different lenses inside the eye; but the lens behind the pupil
Then there is the vitreous cavity and in the very back
The retina , which attaches to the optic nerve , and that’s what goes to the brain
Images come in; they’re bent by the cornea first, then bent again by the lens, and then they focus (hopefully) on the retina
In a perfectly sized eye, in someone who doesn’t need spectacles to see, images come from say, optical infinity, which is for the purposes of this discussion, is about 20 feet or beyond where light rays come in parallel, and they’re bent so that they fall perfectly on the retina
Peter asks him to clarify what fraction of the back of the sphere is considered retina
The whole back of the eye is coded by retina But there is the fovea , mentioned earlier; that’s the point where one casts their gaze The image of the thing one’s looking at falls on the fovea, which is the very center, the bullseye literally of the retina Steven notes, “ When I’m looking at you, images from you are following on the fovea of both of my retinas. ”
But there is the fovea , mentioned earlier; that’s the point where one casts their gaze
The image of the thing one’s looking at falls on the fovea, which is the very center, the bullseye literally of the retina
Steven notes, “ When I’m looking at you, images from you are following on the fovea of both of my retinas. ”

Common types of vision loss and age-related changes

Now, if someone is nearsighted (aka myopia), those images come into focus in a point that is not exactly on the retina, and so that can become a problem Nearsighted means one sees things near well; one sees better up close, and needs glasses to see things at a distance
Farsighted (aka hyperopia) is a little trickier because farsighted people see better at far But their far might also be blurry; it’s just that the near vision is even worse
Peter asks about the person who says they are near and farsighted; is that an accurate statement
No, it’s actually probably that they’re presbyopic , which is that they see well far away Their focusing ability is compromised, typically through age, and they can’t see up close
Peter is very interested in the details of this because a few years ago this rocked his world, it didn’t happen gradually but seemed to happen overnight
Nearsighted means one sees things near well; one sees better up close, and needs glasses to see things at a distance
But their far might also be blurry; it’s just that the near vision is even worse
Their focusing ability is compromised, typically through age, and they can’t see up close

“ Some people wake up on their 40th birthday, and they say, I just can’t see up close anymore, and for others, it’s a little more gradual process ” – Steven Dell

When a person is born, and when they are young, the lens of their eye is extremely elastic It’s like a gummy bear, and it can change shape to bring near objects into focus
With age, and this is universal, the elasticity of the lens goes down, and one is no longer able to zoom focus in So one has to start pushing things farther and farther away or get some optical aid like a pair of spectacles to see up close That process continues as the lens become less elastic and harder, eventually resulting in a cataract where it begins to lose its optical clarity With a cataract, the lens is stiff, hard, and starts to become opaque
Peter asks if this is considered a natural product of aging, the way our skin wrinkles and the elasticity changes, or is it considered a pathology in the way that type II diabetes is a pathology, not necessarily a normal consequence of aging, but it can be avoided?
Steven thinks that cataract formation is a universal component of days on earth He doesn’t recall seeing many people in their 70s without some degree of cataract formation It starts to become universal However, there are things that can pathologically prematurely cause cataract formation Some of them are surprising, like being electrocuted can actually cause premature cataract formation; trauma, head trauma can certainly do it Typically the eye is in the head, and if the head receives trauma, there’s going to be a certain amount of trauma in the eye itself Peter clarifies, the point is, it doesn’t have to be direct trauma to the eye Forces of the brain are presumably also being reverberated through the vitreous fluid The eye is a fluid-containing organ, and when it receives trauma, those same forces come to bear on the eye itself It is more common to develop cataracts when one has direct eye trauma, buteven head trauma alone can predispose someone to cataract formation Certainly, diabetes is a cause of premature cataract formation Steroid use, corticosteroid use can lead to cataract formation
It’s like a gummy bear, and it can change shape to bring near objects into focus
So one has to start pushing things farther and farther away or get some optical aid like a pair of spectacles to see up close
That process continues as the lens become less elastic and harder, eventually resulting in a cataract where it begins to lose its optical clarity
With a cataract, the lens is stiff, hard, and starts to become opaque
He doesn’t recall seeing many people in their 70s without some degree of cataract formation
It starts to become universal
However, there are things that can pathologically prematurely cause cataract formation Some of them are surprising, like being electrocuted can actually cause premature cataract formation; trauma, head trauma can certainly do it Typically the eye is in the head, and if the head receives trauma, there’s going to be a certain amount of trauma in the eye itself Peter clarifies, the point is, it doesn’t have to be direct trauma to the eye Forces of the brain are presumably also being reverberated through the vitreous fluid The eye is a fluid-containing organ, and when it receives trauma, those same forces come to bear on the eye itself It is more common to develop cataracts when one has direct eye trauma, buteven head trauma alone can predispose someone to cataract formation Certainly, diabetes is a cause of premature cataract formation Steroid use, corticosteroid use can lead to cataract formation
Some of them are surprising, like being electrocuted can actually cause premature cataract formation; trauma, head trauma can certainly do it
Typically the eye is in the head, and if the head receives trauma, there’s going to be a certain amount of trauma in the eye itself
Peter clarifies, the point is, it doesn’t have to be direct trauma to the eye
Forces of the brain are presumably also being reverberated through the vitreous fluid
The eye is a fluid-containing organ, and when it receives trauma, those same forces come to bear on the eye itself
It is more common to develop cataracts when one has direct eye trauma, buteven head trauma alone can predispose someone to cataract formation
Certainly, diabetes is a cause of premature cataract formation
Steroid use, corticosteroid use can lead to cataract formation

The lens of the eye

Peter asks if the lens is a vascular structure
It is not; the lens is about the shape and size of an M&M candy, a plain chocolate one It’s got a coating like the candy shell, and the protein inside (the chocolate) is optically clear when one is a kid That protein does not turn over or exchange, but the membrane (the candy coating, the so-called lens capsule ) can allow molecules to diffuse in and out A classic example of this— someone will point out, hey, my vision, my glasses prescription suddenly changed; they became much more nearsighted, or farsighted in the space of a month They go to the eye doctor, and find out that their glasses are totally wrong The first thing Steven thinks of is for them to go get their blood sugar checked because glucose can diffuse into the lens and cause it to swell This will change the shape of the lens The lens becomes physically bigger; it’s like a thicker, more powerful lens Diffusion of glucose into the lens causes an osmotic change The timeframe for that to happen is over a period of several weeks If the blood sugar goes up there may be a lag of a month or two before the vision change And when the blood sugar goes down, same thing; it takes weeks for that to go back to normal
It’s got a coating like the candy shell, and the protein inside (the chocolate) is optically clear when one is a kid
That protein does not turn over or exchange, but the membrane (the candy coating, the so-called lens capsule ) can allow molecules to diffuse in and out
A classic example of this— someone will point out, hey, my vision, my glasses prescription suddenly changed; they became much more nearsighted, or farsighted in the space of a month They go to the eye doctor, and find out that their glasses are totally wrong The first thing Steven thinks of is for them to go get their blood sugar checked because glucose can diffuse into the lens and cause it to swell This will change the shape of the lens The lens becomes physically bigger; it’s like a thicker, more powerful lens Diffusion of glucose into the lens causes an osmotic change The timeframe for that to happen is over a period of several weeks If the blood sugar goes up there may be a lag of a month or two before the vision change And when the blood sugar goes down, same thing; it takes weeks for that to go back to normal
They go to the eye doctor, and find out that their glasses are totally wrong
The first thing Steven thinks of is for them to go get their blood sugar checked because glucose can diffuse into the lens and cause it to swell This will change the shape of the lens The lens becomes physically bigger; it’s like a thicker, more powerful lens
Diffusion of glucose into the lens causes an osmotic change
The timeframe for that to happen is over a period of several weeks
If the blood sugar goes up there may be a lag of a month or two before the vision change
And when the blood sugar goes down, same thing; it takes weeks for that to go back to normal
This will change the shape of the lens
The lens becomes physically bigger; it’s like a thicker, more powerful lens

Blood-retinal barrier

Peter asks if the eye is an immune-privileged site Is it more or less susceptible to systemic infection?
Steven notes the eye itself is certainly prone to damage from systemic infection
There is a blood-retinal barrier in the same way that there’s a blood-brain barrier that protects that highly metabolically active retina from systemic disease
The lens itself is relatively privileged from an immune standpoint It’s within that capsule, and it’s hard for large molecules to get across that, small molecules can
Peter notes this is important from a pharmacotherapy standpoint
Is it more or less susceptible to systemic infection?
It’s within that capsule, and it’s hard for large molecules to get across that, small molecules can

Eye drops in development improve vision by restoring elasticity to the lens

On that topic, Steven mentions a medication being examined as a way of softening the lens to to maybe break some of the disulfide bonds that become a problem and become one of the reasons why the elasticity of the lens is lost This is a lipoic acid choline ester; the safety study was just published
Peter clarifies, “ You’re saying there might be a day when there’s either an optical or injectable substrate that could go into the lens that could delay the onset of farsightedness? ” Yes, and the onset of cataract At the moment it’s in the early experimental phase This compound must be applied in a topical fashion So putting in an eyedrop and that drop has to run the gauntlet of going through the cornea, which has lipid layers and water-soluble layers It’s got to get through all that into the aqueous humor in the front and then through the lens capsule into the lens to actually do its work That’s why this particular drug or compound is a choline ester, because that allows it to get through that lipid layer in the front, through the water-soluble portion of the cornea, and then hopefully into the lens itself This is not easy to do; the lens is a relatively privileged area, both from an immunological, but also a pharmacological standpoint
This is a lipoic acid choline ester; the safety study was just published
Yes, and the onset of cataract
At the moment it’s in the early experimental phase
This compound must be applied in a topical fashion
So putting in an eyedrop and that drop has to run the gauntlet of going through the cornea, which has lipid layers and water-soluble layers
It’s got to get through all that into the aqueous humor in the front and then through the lens capsule into the lens to actually do its work
That’s why this particular drug or compound is a choline ester, because that allows it to get through that lipid layer in the front, through the water-soluble portion of the cornea, and then hopefully into the lens itself
This is not easy to do; the lens is a relatively privileged area, both from an immunological, but also a pharmacological standpoint

Anatomy of the eye from back to front

Everyone recognizes the pupil as the dark part The pupil changes size to dilate and constrict, or is this just the iris moving (the colored part of the eye)?
Yes, the physical aperture of the pupil changes in size; it gets bigger; it gets smaller When someone goes to the eye doctor, and their pupils are dilated, the pupil is physically opened up pharmacologically, and that’s mostly so the doctor can see into the back of the eye to see what’s going on In effect, this forces the iris to move out of the way
The iris almost looks like the aperture of a camera; one can either constrict it or make it bigger
The pupil changes size to dilate and constrict, or is this just the iris moving (the colored part of the eye)?
When someone goes to the eye doctor, and their pupils are dilated, the pupil is physically opened up pharmacologically, and that’s mostly so the doctor can see into the back of the eye to see what’s going on
In effect, this forces the iris to move out of the way

Eye drops that can potentially improve vision [27:30]

Interestingly, one of the big pharmacological frontiers in development are drugs that intentionally shrink the aperture (of the pupils) in the pursuit of increased depth of focus
Students of photography will know that the smaller the aperture, the smaller the hole, the more stuff is in focus at the same time
If one can make the pupil small pharmacologically and get it into the sweet spot (which is probably about 1.6 millimeter) one can suddenly see up close again This expands the depth of focus
Peter clarifies, so another way to manipulate the ability to see things up close is to force the aperture of the lens to be in a position that isn’t necessarily dictated by the availability of light? This relates to the movement of the lens in and out along the Z-axis Also putting aside any other problems that can occur with the lens
Steven explains, “ That’s exactly right. Imagine it’s squinting. ” When one squints, they’re reducing the aperture through with they are looking and filtering out optically If one can get rid of those scattering rays that make the image blurry and only use those parallel rays that happen to be coming parallel off of an object, then one can actually resolve it and see up close again
This expands the depth of focus
This relates to the movement of the lens in and out along the Z-axis
Also putting aside any other problems that can occur with the lens
When one squints, they’re reducing the aperture through with they are looking and filtering out optically
If one can get rid of those scattering rays that make the image blurry and only use those parallel rays that happen to be coming parallel off of an object, then one can actually resolve it and see up close again

Presbyopia

Peter thinks this is a little counterintuitive He’s farsighted and knows that nothing makes it worse, nothing makes presbyopia worse than darkness One example is the difficulty he has reading this train book to his kids in bed It’s dark and the font is small So he has to get his glasses The other place it’s a problem is in a restaurant, where it’s usually poorly lit In both those situations, isn’t his aperture narrowed? Steven explains no, it’s the opposite; “ If you put the sun on something, you’re going to be able to read it because your pupil constricts ” Peter asks if this is why light makes the difference Yes, it’s the pupil effect alone; constriction of the pupil Some of it is the light; there’s much more light energy available to resolve something
He’s farsighted and knows that nothing makes it worse, nothing makes presbyopia worse than darkness
One example is the difficulty he has reading this train book to his kids in bed It’s dark and the font is small So he has to get his glasses
The other place it’s a problem is in a restaurant, where it’s usually poorly lit
In both those situations, isn’t his aperture narrowed? Steven explains no, it’s the opposite; “ If you put the sun on something, you’re going to be able to read it because your pupil constricts ” Peter asks if this is why light makes the difference Yes, it’s the pupil effect alone; constriction of the pupil Some of it is the light; there’s much more light energy available to resolve something
It’s dark and the font is small
So he has to get his glasses
Steven explains no, it’s the opposite; “ If you put the sun on something, you’re going to be able to read it because your pupil constricts ”
Peter asks if this is why light makes the difference
Yes, it’s the pupil effect alone; constriction of the pupil
Some of it is the light; there’s much more light energy available to resolve something

“ So yes, there are competing forces when you reduce the size of the aperture. You’re letting less light in, but the only light you’re letting in are those rays that happen to be parallel in perfect focus, and you can actually see. ” – Steven Dell

In an ongoing clinical trial that he performed to look at this, those competing forces were examined very closely, and they found that the aperture effect, the depth of focus outweighed any loss of vision from loss of light Data not yet published
How long would the effect of these eye drops last?
This actually depends a little on eye color Light eyes tend to react more to any given strength of dilating drop (or constricting)
It would last about 6-8 hours, maybe up to 10 hours So this would be a once-a-day, maybe a twice-a-day eye drop
Peter wonders if this would compromise far vision
No, and what was really interesting is when Steven looked at patients who had their pupil size reduced pharmacologically, their distance vision also improved by the same principle because their depth of focus was so good In the same way that one can squint and make out a highway sign if someone is a little bit nearsighted or a little bit farsighted, or has an astigmatism
Squinting improves vision and pharmacological manipulation of the pupil will do this as well He thinks commercials for these drugs will begin to be aired early in 2022
Peter notes, the complicated aspect of these eye drops is the drug has to make its way into the lens He sees now why that would be more about the cataract issue and not about the presbyopia issue; this would be a much easier way to solve presbyopia because the drug only has to get onto the iris
Steven explains that this is a drug that shrinks the pupil and works in 15 minutes
Versus something that softens the lens that might work in 15 months
Those are very different markets
Lipoic acid choline ester is being pursued as a presbyopia near vision aid or something to reduce the effects of One real goal is to reduce the incidence or delay the onset of cataract formation, which would be really cool Study published in Eye in 2021, Topical lipoic acid choline ester eye drop for improvement of near visual acuity in subjects with presbyopia: a safety and preliminary efficacy trial
Data not yet published
Light eyes tend to react more to any given strength of dilating drop (or constricting)
So this would be a once-a-day, maybe a twice-a-day eye drop
In the same way that one can squint and make out a highway sign if someone is a little bit nearsighted or a little bit farsighted, or has an astigmatism
He thinks commercials for these drugs will begin to be aired early in 2022
He sees now why that would be more about the cataract issue and not about the presbyopia issue; this would be a much easier way to solve presbyopia because the drug only has to get onto the iris
One real goal is to reduce the incidence or delay the onset of cataract formation, which would be really cool
Study published in Eye in 2021, Topical lipoic acid choline ester eye drop for improvement of near visual acuity in subjects with presbyopia: a safety and preliminary efficacy trial

The explanation for different eye colors [33:15]

Darker eye color provides greater protection from UV light

Is there any clear evolutionary explanation for why different eye colors have emerged? What’s the advantage of brown iris versus blue?
The advantage of a brown iris is the protection it offers from UV light , and visible light This works in the same way as darker skin tones So typically, it is common to see dark-eyed people clustered closer to the equator because the visible light and UV light and infrared light or infrared radiation are really destructive
One of the few things that people remember from medical school about the retina is it’s one of the most metabolically active tissues in the body
And because it’s constantly being bombarded with radiation, effectively, it’s prone to free radical formation So what’s called the retinal pigment epithelium , which is the pigmented layer behind the retina, underneath the retina, that is responsible for shielding the vascular supply behind the retina from all of this radiation This is important because the vascular network behind the retina has a very high oxygen tension, and it would be prone to free radical formation if it were constantly being bombarded by UV light, infrared radiation, visible light That’s why one sees in people with more pigment near the equator; and that’s also true of the iris as well
This works in the same way as darker skin tones
So typically, it is common to see dark-eyed people clustered closer to the equator because the visible light and UV light and infrared light or infrared radiation are really destructive
So what’s called the retinal pigment epithelium , which is the pigmented layer behind the retina, underneath the retina, that is responsible for shielding the vascular supply behind the retina from all of this radiation
This is important because the vascular network behind the retina has a very high oxygen tension, and it would be prone to free radical formation if it were constantly being bombarded by UV light, infrared radiation, visible light
That’s why one sees in people with more pigment near the equator; and that’s also true of the iris as well

Physiology of the eye and its connections to the brain [34:45]

The role of rods and cones in vision

Cones are primarily for daytime vision and they’re clustered in the center of ones visual sphere So near the center of the macula , which is the central portion of the retina, and the very center of the macula, is the fovea ; this is where the cones are
The rods are in the periphery and they typically are responsible more for dim illumination vision like night vision And they’re very good at picking up motion So as predators, we want to make sure that we can hone in on where prey is, but as prey ourselves, we want to be able to detect, danger something moving in the periphery
Each rod cell and each cone cell provides one signal They are highly specialized calls They are referred to as photoreceptors and they have stacks of structures within them that are photosensitive; and that causes a depolarization Peter asks if they work like channel opsins; do they use a photon to create an action potential? Yes, once a photon hits a particular cell photoreceptor, there’s a change in the membrane and ions flow; and that’s how a signal is generated And this ion flow ultimately makes its way to the optic nerve and then to the brain
So near the center of the macula , which is the central portion of the retina, and the very center of the macula, is the fovea ; this is where the cones are
And they’re very good at picking up motion
So as predators, we want to make sure that we can hone in on where prey is, but as prey ourselves, we want to be able to detect, danger something moving in the periphery
They are highly specialized calls
They are referred to as photoreceptors and they have stacks of structures within them that are photosensitive; and that causes a depolarization
Peter asks if they work like channel opsins; do they use a photon to create an action potential? Yes, once a photon hits a particular cell photoreceptor, there’s a change in the membrane and ions flow; and that’s how a signal is generated And this ion flow ultimately makes its way to the optic nerve and then to the brain
Yes, once a photon hits a particular cell photoreceptor, there’s a change in the membrane and ions flow; and that’s how a signal is generated
And this ion flow ultimately makes its way to the optic nerve and then to the brain

Visual processing in the brain

Most of the visual processing is in the very back of the brain
And about half of the overall brain structure deals with vision in some capacity That’s why, for example, when people have a stroke, there’s almost always some component of visual involvement in a stroke Someone may have a droopy face on one side and then a limb is droopy as well But if one maps out the visual sphere, they will detect some deficit in the visual sphere for most strokes
Peter puts this in context of brain structure— The brainstem is the most primitive piece of the brain; it is basically responsible for autonomic function Next is midbrain that sits on top of it It is sort of a reptilian brain, a lot of emotion there Then, what in theory distinguishes humans from all the other animals is this remarkable cortical piece that sits on top of it How much of the visual processing is in that neocortex ? Is it virtually all done there? —Yes Pupil responses are controlled by the midbrain, autonomic stuff Visual processing and the actual mapping of the visual sphere has been mapped to the cortex Parts of the brain that are specific to edge detection or moving edge detection has been mapped quite elegantly to the cortex
Peter asks, “ Is there a cross? Is the left doing the right and vice versa? ” Yes, that’s right Remember, information is sent from your left visual sphere to the right side of the brain But information is coming from both eyes
The simplest way to think about something is that at the pituitary , there is something called the optic chiasm This is where the optic nerve crosses; about half the fibers cross So if a visual deficit is in one eye only, this shows that it is in front of the chiasm And if it’s behind the chiasm, it should affect both eyes, maybe asymmetrically, but it should affect both eyes This can be very helpful in localizing where a particular problem is Now, a lot of that’s done through imaging, but there used to be quite an art to this clinical exam
Peter remembers both in neurology and probably neuroanatomy, kind of going into these really crazy tests where he’d see the patient performing the tests and missing a certain thing It looked like they must be faking it; like there’s no way to produce such a bizarre deficit in this one part of this one visual field But then, if there was a tumor, it would totally explain this once one understands how the nerves cross
Steven remarks, “ It kind of goes back to one of your earliest questions, which is, do you think that eye surgeons need to go to medical school? Yes, because we diagnose brain tumors. We find things that are systemic diseases that have ocular manifestations. ”
That’s why, for example, when people have a stroke, there’s almost always some component of visual involvement in a stroke
Someone may have a droopy face on one side and then a limb is droopy as well
But if one maps out the visual sphere, they will detect some deficit in the visual sphere for most strokes
The brainstem is the most primitive piece of the brain; it is basically responsible for autonomic function
Next is midbrain that sits on top of it It is sort of a reptilian brain, a lot of emotion there
Then, what in theory distinguishes humans from all the other animals is this remarkable cortical piece that sits on top of it How much of the visual processing is in that neocortex ? Is it virtually all done there? —Yes
Pupil responses are controlled by the midbrain, autonomic stuff
Visual processing and the actual mapping of the visual sphere has been mapped to the cortex
Parts of the brain that are specific to edge detection or moving edge detection has been mapped quite elegantly to the cortex
It is sort of a reptilian brain, a lot of emotion there
How much of the visual processing is in that neocortex ? Is it virtually all done there? —Yes
Yes, that’s right
Remember, information is sent from your left visual sphere to the right side of the brain
But information is coming from both eyes
This is where the optic nerve crosses; about half the fibers cross
So if a visual deficit is in one eye only, this shows that it is in front of the chiasm
And if it’s behind the chiasm, it should affect both eyes, maybe asymmetrically, but it should affect both eyes
This can be very helpful in localizing where a particular problem is
Now, a lot of that’s done through imaging, but there used to be quite an art to this clinical exam
It looked like they must be faking it; like there’s no way to produce such a bizarre deficit in this one part of this one visual field
But then, if there was a tumor, it would totally explain this once one understands how the nerves cross

Understanding human vision through an evolutionary lens [41:00]

Vision is our most highly developed sense

Peter notes that our eyesight is the one sense humans have that rivals the best in nature
From an evolutionary standpoint, “ Is that because we both had to, as you said, be hunters and be hunted for such a large part of our evolution? ”
Steven thinks yes, “ Imagine you are in the desert and there is a single candle a mile away from you and it’s pitch black. There’s no moon. You can see that ” But in that same desert at high noon, where there may be 200,000 lux illumination, human eye site is still good Humans can see so many, many orders of magnitude of change of illuminations It’s astonishing that our eyes can function in both of those environments
Peter notes humans have a short-lived advantage over some animals when it gets darker There’s a very narrow window at dusk and dawn, where humans have better vision Maybe humans evolved to have good vision in a slightly greater range of light He’s always been amazed at why we did not develop a better sense of smell Humans effectively can’t smell compared to animals; it’s absurd how different it is This is true for our hearing as well; ours is nothing compared to them
Steven notes about vision, “ It’s the one sense that if you asked people which sense they’d be most willing to give up…this is the last one ” It’s very common for patients to grab his arm as they are going into surgery and say, “ Dr. Dell, you don’t understand. My vision is really important to me. I’ve got to see. I’ve got to see. ”
Peter understands the importance of sight relative to other senses In COVID many people lost a sense of smell and a sense of taste, at least transiently This is inconvenient, but it’s totally survivable
But in that same desert at high noon, where there may be 200,000 lux illumination, human eye site is still good
Humans can see so many, many orders of magnitude of change of illuminations
It’s astonishing that our eyes can function in both of those environments
There’s a very narrow window at dusk and dawn, where humans have better vision
Maybe humans evolved to have good vision in a slightly greater range of light
He’s always been amazed at why we did not develop a better sense of smell Humans effectively can’t smell compared to animals; it’s absurd how different it is This is true for our hearing as well; ours is nothing compared to them
Humans effectively can’t smell compared to animals; it’s absurd how different it is
This is true for our hearing as well; ours is nothing compared to them
It’s very common for patients to grab his arm as they are going into surgery and say, “ Dr. Dell, you don’t understand. My vision is really important to me. I’ve got to see. I’ve got to see. ”
In COVID many people lost a sense of smell and a sense of taste, at least transiently This is inconvenient, but it’s totally survivable
This is inconvenient, but it’s totally survivable

“It’s hard to function in the world as a blind person. It’s a fear that many of us have.” – Steven Dell

It’s a sense that people value very highly
And also evolutionarily it’s valued highly just owing to the fact that so much of the brain is devoted to vision

Vision loss due to trauma can often be prevented

Peter recalls, “ When I was a kid, we did so many dumb things without ever any concern for our eyes. I just don’t think our parents knew enough and we didn’t think about it. So I’d be out in the backyard, chucking things around, cutting wood, smashing rocks, never a thought to put on safety goggles. And now my kids, who are both completely obsessed with cutting down trees and they’re very active outdoors. I mean, they just know, you’re wearing your safety goggles if you do that stuff, because I’m totally paranoid they’re going to have one of these tragic accidents. ”
Steven agrees, this is a good PSA; he sees a lot of eye injuries

“ I think injuries are one of the main causes of devastating visual loss in young people ” – Steven Dell

In general, almost all of the big causes and movers of visual loss are senescence-related or age-related But in young people, it’s trauma
Blunt trauma is the most common eye injury he sees
The eye is pretty well protected with the brow and the cheek, but there are certain things that can get in there and can directly impact the eye
In a young person, trauma is something one has to watch out for
Peter asks, “ What is the velocity at which we can’t out blink it? ” “ Because the other day my son was smashing beads and he didn’t want to put his safety goggles on. And I was like, “Look buddy, you got to get these things on.” And he goes, “No, dad.” And he’s like, “Why?” And I said, “Because you’re hitting sharp objects with a sharp object. If one of them flies up and hits your eye,” and he goes, “I would see it. And I would close my eyes.” And I’m like, “No you wouldn’t, buddy.” ” Steven agrees, you wouldn’t blink in time to keep objects like this out Peter notes that some objects move slower; “ If somebody’s throwing you a ball and you misjudge it, you’re going to blink. That’s slow enough that you can catch it. ” Steven agrees but points out there are other objects that move faster He’s operated on a number of major league baseball players and for them seeing the laces on the ball as hitters is enormous; it’s their career It’s the difference between them hitting well or average And some of these players that he’s operated on have been 20/20 before they had surgery, but they wanted to be 20/15 or 20/10
But in young people, it’s trauma
“ Because the other day my son was smashing beads and he didn’t want to put his safety goggles on. And I was like, “Look buddy, you got to get these things on.” And he goes, “No, dad.” And he’s like, “Why?” And I said, “Because you’re hitting sharp objects with a sharp object. If one of them flies up and hits your eye,” and he goes, “I would see it. And I would close my eyes.” And I’m like, “No you wouldn’t, buddy.” ”
Steven agrees, you wouldn’t blink in time to keep objects like this out
Peter notes that some objects move slower; “ If somebody’s throwing you a ball and you misjudge it, you’re going to blink. That’s slow enough that you can catch it. ”
Steven agrees but points out there are other objects that move faster
He’s operated on a number of major league baseball players and for them seeing the laces on the ball as hitters is enormous; it’s their career It’s the difference between them hitting well or average And some of these players that he’s operated on have been 20/20 before they had surgery, but they wanted to be 20/15 or 20/10
It’s the difference between them hitting well or average
And some of these players that he’s operated on have been 20/20 before they had surgery, but they wanted to be 20/15 or 20/10

Enhancing vision beyond 20/20 [47:00]

What is 20/20 vision and can this be enhanced?

20/20 simply means that one can see at 20 feet what a “normal” person can see at 20 feet
If one’s vision is 20/10, they can see at 20 feet what a normal person has to get 10 feet up to in order to see So 20/10 is better than 20/20
So some of these major league baseball players want to be 20/10 or 20/15 He’s been able to achieve that with modern forms of laser vision correction
Steven had a discussion yesterday with a guy who owns a soccer team and he said, “ Have you ever had your players tested for their vision? ” The guy sort of froze and turned white for a second; and he just said, “I t’s so crazy you say that because we put them through this barrage of tests physically to see what their heart, their lungs, their kidneys, all that stuff, we didn’t check their vision. ”
There are ways to boost human performance beyond 20/20
The theoretical limit of how well one can see is defined by essentially the pixelation of their retina This is the spacing of the cells of those photoreceptors discussed earlier This varies from person to person, but it’s somewhere in the vicinity of about 20/08 or so With a sharp enough image, one could theoretically see better than 20/10 And the only way one can really achieve that is to remove some of the optical irregularities that everyone is born with and somehow neutralize them along with the glasses prescription Currently, this can be achieved laser vision correction
So 20/10 is better than 20/20
He’s been able to achieve that with modern forms of laser vision correction
The guy sort of froze and turned white for a second; and he just said, “I t’s so crazy you say that because we put them through this barrage of tests physically to see what their heart, their lungs, their kidneys, all that stuff, we didn’t check their vision. ”
This is the spacing of the cells of those photoreceptors discussed earlier
This varies from person to person, but it’s somewhere in the vicinity of about 20/08 or so
With a sharp enough image, one could theoretically see better than 20/10
And the only way one can really achieve that is to remove some of the optical irregularities that everyone is born with and somehow neutralize them along with the glasses prescription Currently, this can be achieved laser vision correction
Currently, this can be achieved laser vision correction

Laser vision correction compared to contact lenses

Peter asks, “ Why would it be beneficial to an athlete who, for understandable reasons, needs the best vision possible to undergo laser corrective surgery versus just using contact lenses to accomplish the same thing? Is that possible? ”
Let’s first consider contact lenses; anyone who’s ever worn contact lenses knows that when they put in a brand new pair, they can see pretty well with them But then the eye begins to regard that contact lens as a foreign object So one’s body just begins to attack it, coat it with all sorts of immunological debris One is susceptible to pollen, dust, whatever it is that coats this formerly pristine object And let’s say there is correction for astigmatism in that contact lens, where its orientation is important Every time one blinks, that contact lens moves a little bit All of those factors contribute to optical performance that is less than what could be achieved with spectacles or laser vision correction In particular, soft contact lenses do a very, very good job, but they typically don’t provide superhuman vision performance
Peter recalls, “ It’s funny, I experimented two years ago with a stronger prescription than normal to get me to 20/15 in my dominant eye for archery. ”
Steven comments this must have goofed-up his near vision Yea, that was the problem Peter abandoned it immediately after 6 months of suffering It made his presbyopia worse
But then the eye begins to regard that contact lens as a foreign object
So one’s body just begins to attack it, coat it with all sorts of immunological debris
One is susceptible to pollen, dust, whatever it is that coats this formerly pristine object
And let’s say there is correction for astigmatism in that contact lens, where its orientation is important
Every time one blinks, that contact lens moves a little bit
All of those factors contribute to optical performance that is less than what could be achieved with spectacles or laser vision correction
In particular, soft contact lenses do a very, very good job, but they typically don’t provide superhuman vision performance
Yea, that was the problem
Peter abandoned it immediately after 6 months of suffering
It made his presbyopia worse

Astigmatism: definition, cause, and high prevalence [51:30]

Steven describes astigmatism as when the eye is shaped like a football instead of a basketball
Specifically the cornea , the very front part of the eye, typically The cornea is about as thick as a credit card, about 500-550 microns (half a millimeter)
The cornea is about as thick as a credit card, about 500-550 microns (half a millimeter)

Figure 2. Anatomy of the eye, the cornea. Image credit: Britannica

There can be astigmatism in the lens itself, the lens behind the pupil
Peter has a corneal astigmatism; that’s the normal one This simply means the eye is not perfectly shaped; it’s a bit oblong like an egg or football Steven compares it to an American football, “ So if you are walking along the laces of the football, you would encounter a fairly gradual curve. But if you took a right turn and walked it perpendicular, it would be very steep. ” That means that the power differs by meridian; so Peter needs a different glasses prescription in this meridian versus this meridian
The prevalence of astigmatism is pretty high Around 60% of patients with a glasses prescription have some significant degree of astigmatism
This simply means the eye is not perfectly shaped; it’s a bit oblong like an egg or football
Steven compares it to an American football, “ So if you are walking along the laces of the football, you would encounter a fairly gradual curve. But if you took a right turn and walked it perpendicular, it would be very steep. ”
That means that the power differs by meridian; so Peter needs a different glasses prescription in this meridian versus this meridian
Around 60% of patients with a glasses prescription have some significant degree of astigmatism

Evolution of vision problems

Peter wonders why poor vision has been allowed to evolve, “ Vision that would impair your ability to survive through reproductive age probably didn’t evolve ” Maybe there was a day when the genetic variability of eyes was broad enough that a subset of people had really poor vision; the type of people who maybe aren’t around today? Steven agrees, “ This is a super interesting topic and it shows you how plastic the evolutionary or actually the adaptive component of the eyeball is itself. ” The length of the eye is really what determines whether one is nearsighted or farsighted This is the distance from front to back, anterior-posterior length of the eyeball Primarily, that is the main driver as to whether one is nearsighted or farsighted Those who are in the know and are watching this or listening to it also realize that sometimes it’s the curvature of the cornea that contributes to whether someone is nearsighted or farsighted
Maybe there was a day when the genetic variability of eyes was broad enough that a subset of people had really poor vision; the type of people who maybe aren’t around today?
Steven agrees, “ This is a super interesting topic and it shows you how plastic the evolutionary or actually the adaptive component of the eyeball is itself. ”
The length of the eye is really what determines whether one is nearsighted or farsighted This is the distance from front to back, anterior-posterior length of the eyeball Primarily, that is the main driver as to whether one is nearsighted or farsighted
Those who are in the know and are watching this or listening to it also realize that sometimes it’s the curvature of the cornea that contributes to whether someone is nearsighted or farsighted
This is the distance from front to back, anterior-posterior length of the eyeball
Primarily, that is the main driver as to whether one is nearsighted or farsighted

Nearsightedness (myopia): causes, epidemic in children, and prevention strategies [54:15]

But let’s say for the purposes of this discussion that it’s the length of the eyeball that is the main reason why someone is nearsighted or not or farsighted. So a very nearsighted person has a very long eyeball
Peter wants clarification, with a very long anterior-posterior axis, one is going to have a hard time seeing things far away Is that because the further away something is, the harder it is to focus all the light coming in?
Steven explains, when most of one’s visual environment is close, then the light rays from that close object are diverging So these light rays are falling behind the retina of someone who’s perfectly targeted for distance The eyeball is really smart and it says, “ Okay, so you’re telling me everything is here, close up. I know, I’ll just grow longer so that these near objects are in perfect focus. ” And that is exactly what happens This can happen over a period of months If a young person exclusively performs near tasks, their eye will grow longer so that those near objects are in perfect focus
So a very nearsighted person has a very long eyeball
Is that because the further away something is, the harder it is to focus all the light coming in?
So these light rays are falling behind the retina of someone who’s perfectly targeted for distance
The eyeball is really smart and it says, “ Okay, so you’re telling me everything is here, close up. I know, I’ll just grow longer so that these near objects are in perfect focus. ” And that is exactly what happens
This can happen over a period of months If a young person exclusively performs near tasks, their eye will grow longer so that those near objects are in perfect focus
If a young person exclusively performs near tasks, their eye will grow longer so that those near objects are in perfect focus
Peter comments “ So if you could do an awful experiment… ” Steven says, “ It’s been done ” This is what is happening in our current society; children looking at screens, near objects, for hours on end and not going outside often develop nearsightedness
There are two drivers of nearsightedness in the plastic developing human 1) Deprivation from outdoor light 2) Near work
Many of studies of children have been done in Asia, where there is an epidemic right now of myopia of astonishing proportions About 90% of the population is now nearsighted in certain southeastern nation cities When that becomes such a dominant phenotype, something is really oddly off
Peter notes, “ this really transcends evolution because if you can change something in years or months ”
Steven clarifies, “ It’s not evolutionary. It’s adaptive within the eyeball itself. ”
Groups of 7- to 11-year-old children have been studies Send half of them outside for 80 minutes during the school day for recess Keep half of them indoors for recess The risk of or the incidence of nearsightedness is half in the group that went outside So the risk of nearsightedness can be cut in half by going outside Without any instruction to go and look at things far away, but just by the very fact that outside there’s so much more to see and ones is going to be looking further out
This has been further studied in terms of is it just being outside or is it the light? It’s actually both But the light is really the most important driver of protection from nearsightedness So if one is outside on a bright sunny day, they’re releasing a fair bit of dopamine from the retina and dopamine inhibits the growth of the eye So the worst thing to do is stay inside in a dimly lit room and perform near tasks That raises the risk of nearsightedness 16 fold compared to kids who go outside
Peter asks if epidemiological studies show that the further one is from the equator the greater the risk of nearsightedness, simply based on the light part of this argument?
Yes; there is some data that shows that And not only that, they’ve taken children and given them equal intervals of outdoor activity, but the ones who had noontime outdoor activity did better than the ones who were outdoors at 8:00 AM, when there was less illumination Further, it is known from animal models that it is illumination that is critical in this dopamine release So does that mean more skylights in classrooms or more windows or more natural light would be beneficial? Could artificial light mimic some of the sunlight by making these rooms brighter and prevent some of this myopia epidemic?
Peter reasons, “ Is a photon, a photon, a photon? ” How does this work
It is not known whether that’s the case because there’s a whole spectrum of light
So is the blue light more important? This is tangential One hears all this negativity about blue light Blue light is critical for wakefulness, for attention, and Steven thinks for preventing myopia
Steven says, “ It’s been done ”
This is what is happening in our current society; children looking at screens, near objects, for hours on end and not going outside often develop nearsightedness
1) Deprivation from outdoor light
2) Near work
About 90% of the population is now nearsighted in certain southeastern nation cities
When that becomes such a dominant phenotype, something is really oddly off
Send half of them outside for 80 minutes during the school day for recess
Keep half of them indoors for recess
The risk of or the incidence of nearsightedness is half in the group that went outside So the risk of nearsightedness can be cut in half by going outside Without any instruction to go and look at things far away, but just by the very fact that outside there’s so much more to see and ones is going to be looking further out
So the risk of nearsightedness can be cut in half by going outside
Without any instruction to go and look at things far away, but just by the very fact that outside there’s so much more to see and ones is going to be looking further out
It’s actually both
But the light is really the most important driver of protection from nearsightedness
So if one is outside on a bright sunny day, they’re releasing a fair bit of dopamine from the retina and dopamine inhibits the growth of the eye
So the worst thing to do is stay inside in a dimly lit room and perform near tasks That raises the risk of nearsightedness 16 fold compared to kids who go outside
That raises the risk of nearsightedness 16 fold compared to kids who go outside
And not only that, they’ve taken children and given them equal intervals of outdoor activity, but the ones who had noontime outdoor activity did better than the ones who were outdoors at 8:00 AM, when there was less illumination
Further, it is known from animal models that it is illumination that is critical in this dopamine release
So does that mean more skylights in classrooms or more windows or more natural light would be beneficial? Could artificial light mimic some of the sunlight by making these rooms brighter and prevent some of this myopia epidemic?
Could artificial light mimic some of the sunlight by making these rooms brighter and prevent some of this myopia epidemic?
One hears all this negativity about blue light
Blue light is critical for wakefulness, for attention, and Steven thinks for preventing myopia

Other risks associated with nearsightedness

By the way, myopia (or nearsightedness) is not just the inconvenience of wearing glasses or contact lenses or having laser vision correction when one is 23 years old
There are pathologies that are much more common in very nearsighted patients compared to the general population It’s much more common to see cataract formation in myopic patients They get something called myopic macular degeneration They’re at risk for glaucoma They’re at risk for tears and detachments of the retina These are disease-associated conditions
It’s much more common to see cataract formation in myopic patients
They get something called myopic macular degeneration
They’re at risk for glaucoma
They’re at risk for tears and detachments of the retina
These are disease-associated conditions

Considering vision from an evolutionary perspective—Is there genetic susceptibility to vision loss?

Peter returns to his evolutionary question, “ it’s quite possible that over hundreds of millions of years, any deficit in vision that would’ve prevented you from reproducing or impaired your ability to escape a predator would’ve taken that out. So from a genetic standpoint, our vision should be very good. ”
Steven clarifies that vision is very good in non-literate societies In hunter-gatherer tribes, there is no nearsightedness; it just doesn’t happen
Peter finds this amazing and asks, “ This suggests that because my parents wore glasses, I should wear glasses, is not true. Or is there an epigenetic part of this? ”
Both are true; there is a genetic component For siblings of individuals who wear spectacles, there is a higher incidence of myopia or hyperopia This could be susceptibility It is not known whether parents of reading children were reading children themselves; so it’s hard to separate out the genetic component; there does seem to be a genetic component as well But the environmental component seems to be way stronger and more powerful Take parents who don’t wear spectacles and put their child in a dark room and give them an electronic device or a book or whatever it is and have that child focus at near for hours on end, odds are they’re much more at risk for developing nearsightedness
Peter thinks about his kids; his wife has perfect vision and his diopter is -3 and -4 What does that mean in terms of the 20 scale? It depends on how much he squints when he looks at the eye chart Steven honestly doesn’t attach a lot of significance to the 20/100 or 20/80, whatever it is Peter is probably in that ballpark, maybe 20/100 Peter notes that he’s at the point where without contacts, he can’t drive, he can’t do anything And some people are -15 They literally must have their glasses near the bedside Peter can spend the first hour of the day without contact lenses It’s easier for him to read without his contacts
In hunter-gatherer tribes, there is no nearsightedness; it just doesn’t happen
For siblings of individuals who wear spectacles, there is a higher incidence of myopia or hyperopia This could be susceptibility It is not known whether parents of reading children were reading children themselves; so it’s hard to separate out the genetic component; there does seem to be a genetic component as well But the environmental component seems to be way stronger and more powerful Take parents who don’t wear spectacles and put their child in a dark room and give them an electronic device or a book or whatever it is and have that child focus at near for hours on end, odds are they’re much more at risk for developing nearsightedness
This could be susceptibility
It is not known whether parents of reading children were reading children themselves; so it’s hard to separate out the genetic component; there does seem to be a genetic component as well
But the environmental component seems to be way stronger and more powerful Take parents who don’t wear spectacles and put their child in a dark room and give them an electronic device or a book or whatever it is and have that child focus at near for hours on end, odds are they’re much more at risk for developing nearsightedness
Take parents who don’t wear spectacles and put their child in a dark room and give them an electronic device or a book or whatever it is and have that child focus at near for hours on end, odds are they’re much more at risk for developing nearsightedness
What does that mean in terms of the 20 scale?
It depends on how much he squints when he looks at the eye chart
Steven honestly doesn’t attach a lot of significance to the 20/100 or 20/80, whatever it is Peter is probably in that ballpark, maybe 20/100
Peter notes that he’s at the point where without contacts, he can’t drive, he can’t do anything And some people are -15 They literally must have their glasses near the bedside Peter can spend the first hour of the day without contact lenses It’s easier for him to read without his contacts
Peter is probably in that ballpark, maybe 20/100
And some people are -15
They literally must have their glasses near the bedside
Peter can spend the first hour of the day without contact lenses It’s easier for him to read without his contacts
It’s easier for him to read without his contacts

Near tasks such as reading and extended screen time can result in nearsightedness

Steven notes that things are very well in focus at a typical normal reading distance for Peter; so his eyes have been tuned postnatally for near work That is a result of his development Peter must have spent a lot of time reading or doing near tasks Peter notes, “ I grew up in Canada. So from a light perspective, it wasn’t so great. You had two months of no light whatsoever, but I didn’t watch TV much as a kid, maybe 30 minutes a day. I was mostly outdoors. I’ll tell you, this is funny. I didn’t need my first pair of glasses till college. So it could also be that this happened later in my life as a result of more book work. ”
The classic example Steven sees is law students who have great vision when they enter law school but then they read for 12 hours a day and then they come in and they say, “ You know, I think my vision’s going. ” He looks at them and sure enough, they’ve become nearsighted That’s not rare in many graduate school situations, where there’s just grinding reading for hours on end
That is a result of his development
Peter must have spent a lot of time reading or doing near tasks
Peter notes, “ I grew up in Canada. So from a light perspective, it wasn’t so great. You had two months of no light whatsoever, but I didn’t watch TV much as a kid, maybe 30 minutes a day. I was mostly outdoors. I’ll tell you, this is funny. I didn’t need my first pair of glasses till college. So it could also be that this happened later in my life as a result of more book work. ”
He looks at them and sure enough, they’ve become nearsighted
That’s not rare in many graduate school situations, where there’s just grinding reading for hours on end

Preventing nearsightedness in children

So Peter thinks this is very important for his kids; it’s too late for him
Steven agrees, get them outside Make sure they’re spending a couple hours outside a day The data also suggest that good illumination would be helpful as opposed to poor illumination But he doesn’t want to discourage near activities because those are really important developmentally
Peter wonders if the opposite is true for hunter-gatherers or illiterate societies who are outside all the time They don’t develop nearsightedness Do they develop farsightedness?
No, Steven thinks they are fairly well tuned to distance vision, to prey hunting, etc.
Make sure they’re spending a couple hours outside a day
The data also suggest that good illumination would be helpful as opposed to poor illumination
But he doesn’t want to discourage near activities because those are really important developmentally
They don’t develop nearsightedness
Do they develop farsightedness?

Cataracts: impact of aging and how they can be repaired [1:05:00]

Now, there’s a whole host of other problems that come into play once one has outlived their genetic usefulness, after one has reproduced and imparted their knowledge onto the next generation Then one can go ahead and get cataracts because they’re done from a standpoint of genetic utility
Peter asks if developing cataracts is functionally like atherosclerosis It’s something that has no bearing on reproductive capacity, but is otherwise inevitable to our species Steven agrees, it seems to be fairly inevitable to our species He hasn’t seen patients in their 70s typically who don’t have some cataract formation Now there are patients who are 80 that are still functioning with cataracts, but the optical clarity of their lenses has degraded to the point that it’s not the way it was when they were 20 Maybe their visual needs are significantly reduced
Then one can go ahead and get cataracts because they’re done from a standpoint of genetic utility
It’s something that has no bearing on reproductive capacity, but is otherwise inevitable to our species
Steven agrees, it seems to be fairly inevitable to our species
He hasn’t seen patients in their 70s typically who don’t have some cataract formation
Now there are patients who are 80 that are still functioning with cataracts, but the optical clarity of their lenses has degraded to the point that it’s not the way it was when they were 20 Maybe their visual needs are significantly reduced
Maybe their visual needs are significantly reduced

“ But if you took an 80-year-old lens and you put it in a 20-year-old person, they would be shocked at how poor their vision is ” – Steven Dell

Vision loss due to light exposure and trauma

Peter recalls, earlier Steven mentioned that senescent cells or their soluble secretory products probably play a role in the loss of vision as one ages
In the lens, Steven thinks it’s mostly that the lens proteins are degrading or becoming damaged over time
Maybe UV light contributes to this
It’s known that light exposure is related to cataract formation, as are some of the other things previously discussed like: glucose going into the lens, corticosteroid use
It is not known what it is specifically about trauma that causes a premature loss of clarity of the lens proteins The trauma worries Peter because he boxed for so long He took way too many hits to the head Steven comments “ The cataract would be the easiest thing to fix ”
The trauma worries Peter because he boxed for so long He took way too many hits to the head
Steven comments “ The cataract would be the easiest thing to fix ”
He took way too many hits to the head

“ Cataract surgery today is like a four or five-minute procedure, and it’s astonishingly effective ” – Steven Dell

Cataract surgery implants a new lens

Cataract surgery typically is not repeated; it’s a once in a lifetime deal
Peter asks what the cataract patient experiences; is it like wearing glasses that are dirty
The first thing they probably notice is changes in their night vision Glare, halos, streaks off of lights at night, problems with contrast sensitivity, for those who can appreciate that loss of contrast These are really early signs of cataract formation This is common at age 54 or 64
Steven typically lets the patient decide when it’s the right time for them to have the surgery once he determines that the cataract is visually significant
There are people who elect to have their cataracts removed earlier than they really need them removed as a means of getting rid of their glasses prescription
Now the implant lenses that are put in to replace the cataract, they have advanced in terms of function to the point that they can fix the near vision, as well as the distance vision, the astigmatism, the nearsightedness, the farsightedness, the presbyopia These are all correctable with artificial lenses that he puts in the eye to replace the cataract
There’s a fascinating history about the evolution of intraocular lenses (IOL) But back in the days of his residency, the implant lenses that were put in were simply designed to give the patient good vision with spectacles These lens only replaced the cloudy lens with something that was in the ballpark of good distance vision; the patient would still need to wear spectacles after the surgery
Peter asks, “ Does all cataract surgery involve the placement of an extra lens? ” Yes, virtually every cataract surgery he performs involves removal of the cataract and replacing it with an artificial lens To clarify, “ Does that mean removing the entire lens or removing a diseased part of the lens that has the cataract in it? ” Remember the analogy of the M&M candy The shell is left He opens a hole in the front of the shell and takes out all the chocolate Now it is kind of like a flattened bowl; it looks like a Japanese teapot flattened The implant lens is placed in that bowl; the bowl holds the implant in place
The implant lens is a bendable plastic object; it can be folded up and put through a tiny incision then opened up again This folding and opening of the implant lens was a very big advancement that happened in the 1980’s
Glare, halos, streaks off of lights at night, problems with contrast sensitivity, for those who can appreciate that loss of contrast
These are really early signs of cataract formation
This is common at age 54 or 64
These are all correctable with artificial lenses that he puts in the eye to replace the cataract
But back in the days of his residency, the implant lenses that were put in were simply designed to give the patient good vision with spectacles
These lens only replaced the cloudy lens with something that was in the ballpark of good distance vision; the patient would still need to wear spectacles after the surgery
Yes, virtually every cataract surgery he performs involves removal of the cataract and replacing it with an artificial lens
To clarify, “ Does that mean removing the entire lens or removing a diseased part of the lens that has the cataract in it? ”
Remember the analogy of the M&M candy The shell is left He opens a hole in the front of the shell and takes out all the chocolate Now it is kind of like a flattened bowl; it looks like a Japanese teapot flattened The implant lens is placed in that bowl; the bowl holds the implant in place
The shell is left
He opens a hole in the front of the shell and takes out all the chocolate
Now it is kind of like a flattened bowl; it looks like a Japanese teapot flattened
The implant lens is placed in that bowl; the bowl holds the implant in place
This folding and opening of the implant lens was a very big advancement that happened in the 1980’s

Cataract treatment in ancient times

Prior to this is a really amazing series of stories
In the ancient world, if one had cataracts, the way they dealt with it is that they would just poke the lens of the eye backward, and it would drop down into the bottom of the eye so that the person now had a clear optical pathway, again, to let light in
This took someone who was functionally blind and allowed them to see shapes
They no longer have a lens, so there is no way to focus
But it’s basically like taking someone who has no light transmission and saying, “ We’re going to let unfocused light go through. ”
This is what happened in in Hammurabi time The fact that they knew enough to do that is kind of amazing
There’ve been artifacts uncovered; a lot of them were made out of gold They would take a gold needle and poke it through the cornea The procedure was called couching They would just poke the lens, and it would detach from its ligamentous attachments and then drop down into the bottom of the cavity of the eye There are some of these artifacts from Egypt This was done in China It was certainly done in ancient Greece; that was how they dealt with cataracts back then Peter notes, “ you’re talking about, what, 5,000 years ago, right. This is not… In an evolutionary timescale that’s a pittance, right ” Would it be better to be the poorest person on earth today than to be the Pharaoh of Egypt 5,000 years ago Steven thinks in many ways, yes
The fact that they knew enough to do that is kind of amazing
They would take a gold needle and poke it through the cornea
The procedure was called couching
They would just poke the lens, and it would detach from its ligamentous attachments and then drop down into the bottom of the cavity of the eye
There are some of these artifacts from Egypt
This was done in China
It was certainly done in ancient Greece; that was how they dealt with cataracts back then
Peter notes, “ you’re talking about, what, 5,000 years ago, right. This is not… In an evolutionary timescale that’s a pittance, right ” Would it be better to be the poorest person on earth today than to be the Pharaoh of Egypt 5,000 years ago Steven thinks in many ways, yes
Would it be better to be the poorest person on earth today than to be the Pharaoh of Egypt 5,000 years ago
Steven thinks in many ways, yes

The first implant lens

Fast forward to right after World War II ; there’s an ophthalmologist in the UK named Harold Ridley He notices that some of the RAF fighters (Royal Air Force) would have fragments of their plexiglass canopy inside their eyeballs This canopy would shatter when they were fired upon Shards of plexiglass essentially would be inside the eyeball And the dilemma was what to do about this He learned very early on that these fragments were biologically inert The eye was perfectly happy and people could walk around the rest of their lives with a shard of sharp plexiglass inside their eyeball This is a foreign object that has now entered the eye, not necessarily in the human lens; it might even be in the vitreous cavity , or in the front of the eye
So the light bulb goes off; he realizes one can put plexiglass (which is essentially polymethyl methacrylate ) in the eye, and the body doesn’t really care that it’s there, doesn’t mount an immune response
So in Ridley’s book (which Steven has read, it’s really amazing) some intern asked him, “W ell, when you take this cataract out, are you going to replace it with a new lens? ” He looked at this young intern in a British fashion, and Steven assumes he said, “T hat’s the stupidest question I’ve ever heard. ” And then he went home and thought, “ Wait a minute, that’s brilliant. We should replace it. “ Then they lathed a lens from some spectacle maker that was about the size and shape of the human lens They put 8 of these in patients There’s amazing footage of these early operations They dropped the lens on the floor, and of course, it’s the only one they had; so they pick it up, and rinse it off And it’s fine; they put it in These patients did shockingly well, and this was viewed as heresy There was 20 years of, “ You’re blinding people. ” But eventually, the technology won out and became standard There must have been bad outcomes in the beginning Like any new technology, the first iteration of it is probably terrible and maybe just a little bit less terrible than the alternative Now it’s ubiquitously used
He notices that some of the RAF fighters (Royal Air Force) would have fragments of their plexiglass canopy inside their eyeballs This canopy would shatter when they were fired upon Shards of plexiglass essentially would be inside the eyeball
And the dilemma was what to do about this
He learned very early on that these fragments were biologically inert The eye was perfectly happy and people could walk around the rest of their lives with a shard of sharp plexiglass inside their eyeball This is a foreign object that has now entered the eye, not necessarily in the human lens; it might even be in the vitreous cavity , or in the front of the eye
This canopy would shatter when they were fired upon
Shards of plexiglass essentially would be inside the eyeball
The eye was perfectly happy and people could walk around the rest of their lives with a shard of sharp plexiglass inside their eyeball
This is a foreign object that has now entered the eye, not necessarily in the human lens; it might even be in the vitreous cavity , or in the front of the eye
He looked at this young intern in a British fashion, and Steven assumes he said, “T hat’s the stupidest question I’ve ever heard. ” And then he went home and thought, “ Wait a minute, that’s brilliant. We should replace it. “
Then they lathed a lens from some spectacle maker that was about the size and shape of the human lens
They put 8 of these in patients
There’s amazing footage of these early operations They dropped the lens on the floor, and of course, it’s the only one they had; so they pick it up, and rinse it off And it’s fine; they put it in These patients did shockingly well, and this was viewed as heresy There was 20 years of, “ You’re blinding people. ” But eventually, the technology won out and became standard There must have been bad outcomes in the beginning Like any new technology, the first iteration of it is probably terrible and maybe just a little bit less terrible than the alternative Now it’s ubiquitously used
They dropped the lens on the floor, and of course, it’s the only one they had; so they pick it up, and rinse it off
And it’s fine; they put it in
These patients did shockingly well, and this was viewed as heresy There was 20 years of, “ You’re blinding people. ” But eventually, the technology won out and became standard There must have been bad outcomes in the beginning
Like any new technology, the first iteration of it is probably terrible and maybe just a little bit less terrible than the alternative
Now it’s ubiquitously used
There was 20 years of, “ You’re blinding people. ” But eventually, the technology won out and became standard There must have been bad outcomes in the beginning
There must have been bad outcomes in the beginning

Current technology used in cataract surgery

Peter didn’t realize it until Steven said it, but polymethyl methacrylate is all over the body in terms of joints A replacement knee joint, the tibial plateau, he thinks it’s made out of polymethyl methacrylate So presumably, there’s something about it that is just invisible to the immune system
Steven notes that this material isn’t used anymore because it’s stiff It’s not deformable In the old days, they had to make a fairly large incision to get it in First, the cataract was removed and then the implant lens placed in 2 converging technologies made that go away: 1) They were able to take the cataract out through a tiny in incision They break it up; essentially they emulsify it with ultrasound Now sometimes they use a femtosecond laser to break up parts of it But the bottom line is that they can remove the cataract through about a two-something millimeter incision, which is very small, like the thickness of a pencil lead 2) The implant lens can be folded up and put them through that same tiny incision and then they can open up and be exactly where they need to be
Now, why is it important for the incision to be small? A big incision takes longer to heal It also induces astigmatism It’s best for the incision to be tiny
Going back to the M&M analogy, Peter asks, “ Does the coating on the surface of the M&M grow back? ” The answer is no; whatever hole they put there remains Sometimes the coating, the M&M candy shell, can begin to opacify after surgery; this can be treated in the office with a laser where he can just disrupt that coating
Peter remarks, “ My mom’s 72nd birthday is today. I don’t know if she’s had any issues with cataracts. But if not, she’s due for them. My dad has. He’s 83. I’m trying to think. He must have had surgery by now, right? ” The odds are they have cataracts
Peter remarks, “ this must be a game-changer for a patient ”
Steven does cataract surgery in an ambulatory surgery center He notes that Peter’s Dad probably didn’t talk about it because this is such a non-event A patient goes in for cataract surgery, and the next day they’re back to their regular activities
Cataract surgery can greatly improve the ability to see Especially now that the implant lenses can correct the near vision and the distance vision This in addition to the added clarity from just removing the cataract, patients typically have this benefit of not needing spectacles
The number 1 risk of this surgery is infection It’s extraordinarily unusual; less than 1 in 10,000 cases results in a serious infection It’s like any other surgery in the body He looks for bleeding, damage to the inside of the eye He has to to keep tabs on the pressure It’s basically everything that a doctor would look for if they were taking out an appendix, but they’re also dealing with in the eye
Peter asks, “ What fraction of patients do not have a material improvement in their vision? Or have some deterioration of even another subset of vision? ”
This is pretty unusual because the science behind getting the prescription correct or very close to correct is pretty advanced
A replacement knee joint, the tibial plateau, he thinks it’s made out of polymethyl methacrylate
So presumably, there’s something about it that is just invisible to the immune system
It’s not deformable
In the old days, they had to make a fairly large incision to get it in
First, the cataract was removed and then the implant lens placed in
2 converging technologies made that go away: 1) They were able to take the cataract out through a tiny in incision They break it up; essentially they emulsify it with ultrasound Now sometimes they use a femtosecond laser to break up parts of it But the bottom line is that they can remove the cataract through about a two-something millimeter incision, which is very small, like the thickness of a pencil lead 2) The implant lens can be folded up and put them through that same tiny incision and then they can open up and be exactly where they need to be
1) They were able to take the cataract out through a tiny in incision They break it up; essentially they emulsify it with ultrasound Now sometimes they use a femtosecond laser to break up parts of it But the bottom line is that they can remove the cataract through about a two-something millimeter incision, which is very small, like the thickness of a pencil lead
2) The implant lens can be folded up and put them through that same tiny incision and then they can open up and be exactly where they need to be
They break it up; essentially they emulsify it with ultrasound
Now sometimes they use a femtosecond laser to break up parts of it
But the bottom line is that they can remove the cataract through about a two-something millimeter incision, which is very small, like the thickness of a pencil lead
A big incision takes longer to heal
It also induces astigmatism
It’s best for the incision to be tiny
The answer is no; whatever hole they put there remains
Sometimes the coating, the M&M candy shell, can begin to opacify after surgery; this can be treated in the office with a laser where he can just disrupt that coating
The odds are they have cataracts
He notes that Peter’s Dad probably didn’t talk about it because this is such a non-event
A patient goes in for cataract surgery, and the next day they’re back to their regular activities
Especially now that the implant lenses can correct the near vision and the distance vision
This in addition to the added clarity from just removing the cataract, patients typically have this benefit of not needing spectacles
It’s extraordinarily unusual; less than 1 in 10,000 cases results in a serious infection
It’s like any other surgery in the body He looks for bleeding, damage to the inside of the eye He has to to keep tabs on the pressure It’s basically everything that a doctor would look for if they were taking out an appendix, but they’re also dealing with in the eye
He looks for bleeding, damage to the inside of the eye
He has to to keep tabs on the pressure
It’s basically everything that a doctor would look for if they were taking out an appendix, but they’re also dealing with in the eye

Lens implants that can correct and improve vision [1:19:30]

Not everybody gets the same lens; lens to correct vision are expensive and the patient has to pay some extra money to get them
Regular cataract surgery makes no attempt to get rid of spectacles Regular cataract surgery is probably going to be completely covered by a person’s health insurance
One may have to pay thousands of dollars out of pocket if they wanted to get rid of their glasses Patients ask “ Well, what else do I use every waking moment of my life forever? ” They could go on a vacation for a week or two and spend that money, but then the vacation is over He finds that patients value their vision; they value it pretty highly It’s their independence, that they’re trying to preserve
Peter is in awe at how much he didn’t know, “ I thought cataract surgery is literally removing the sort of crud that’s in the lens… I just naively assumed the good stuff would grow back. I never knew you were putting another lens in, let alone that you could actually use the new lens as a way to correct other visual defects. ”
The technology has evolved to the point where he can actually correct those spectacle requirements Now, many of his patients don’t really care about spectacle independence They just want to see well, and that’s easy to achieve But as these lenses have gotten better, the capabilities of ophthalmologists have gotten better
Peter asks, if he needed cataract surgery today, knowing his diopter (-4 and -3 with a slight astigmatism), could his vision be corrected? Yes, but the problem with a lot of these eyes is they are attached quite firmly to people Sometimes the patient’s expectations can be unrealistic in terms of what can be delivered He has to carefully educate them on, “ Well, what can these lenses actually do? Am I going to see a perfect hunter at dusk while still being able to read up close? ” And maybe the answer is yes; maybe the answer is no
Peter asks if the lenses can tune vision for distance or near vision He doesn’t mind wearing contacts, but hates his reading glasses Contacts are easy because he puts them in, in the morning and takes them out at night Reading glasses are annoying because he never remembers to bring them to a restaurant, so he’s shining a phone light on the menu Or he’s reading his kid a book at night and has to pause to get his glasses
This is not an unusual request They can intentionally set one’s vision for near or leave it for near It’s just an optical calculation to set the point of focus where one wants it to be
What gets measured at the clinic? One of the first things that he has to do is make sure that the surface of the cornea is tuned up from a dry eye standpoint Because dry eye patients, the surface of their corneas, it’s not optically pristine; it’s a little distorted Contact lens make this a lot worse; it can throw off his measurements This can throw off the calculation because it’s pretty simple Newtonian physics Knowing the length of the eyeball, the curvature of the front of the eye, the index of refraction of stuff inside the eyeball (how bendy the material is), and considering where the implant lens is going to reside— a calculation can correct for placing the image on the retina The more perfect the shape of the cornea, the better that calculation is This is probably the weak link in the set of measurement they take The length of the eye from front to back can be accurately measured with lasers With light, they can bounce a beam off the back of the retina and know exactly how long the eyeball is It’s almost like sonar , but with light He knows roughly where the implant lens is going to rest when he puts it in If he knows some other dimensions of the eye and uses the front curvature as another piece of data, he can predict what power implant lens to put in
Peter finds this remarkable
Regular cataract surgery is probably going to be completely covered by a person’s health insurance
Patients ask “ Well, what else do I use every waking moment of my life forever? ”
They could go on a vacation for a week or two and spend that money, but then the vacation is over
He finds that patients value their vision; they value it pretty highly
It’s their independence, that they’re trying to preserve
Now, many of his patients don’t really care about spectacle independence
They just want to see well, and that’s easy to achieve
But as these lenses have gotten better, the capabilities of ophthalmologists have gotten better
Yes, but the problem with a lot of these eyes is they are attached quite firmly to people
Sometimes the patient’s expectations can be unrealistic in terms of what can be delivered
He has to carefully educate them on, “ Well, what can these lenses actually do? Am I going to see a perfect hunter at dusk while still being able to read up close? ” And maybe the answer is yes; maybe the answer is no
And maybe the answer is yes; maybe the answer is no
He doesn’t mind wearing contacts, but hates his reading glasses
Contacts are easy because he puts them in, in the morning and takes them out at night
Reading glasses are annoying because he never remembers to bring them to a restaurant, so he’s shining a phone light on the menu Or he’s reading his kid a book at night and has to pause to get his glasses
Or he’s reading his kid a book at night and has to pause to get his glasses
They can intentionally set one’s vision for near or leave it for near
It’s just an optical calculation to set the point of focus where one wants it to be
One of the first things that he has to do is make sure that the surface of the cornea is tuned up from a dry eye standpoint Because dry eye patients, the surface of their corneas, it’s not optically pristine; it’s a little distorted Contact lens make this a lot worse; it can throw off his measurements This can throw off the calculation because it’s pretty simple Newtonian physics
Knowing the length of the eyeball, the curvature of the front of the eye, the index of refraction of stuff inside the eyeball (how bendy the material is), and considering where the implant lens is going to reside— a calculation can correct for placing the image on the retina The more perfect the shape of the cornea, the better that calculation is This is probably the weak link in the set of measurement they take The length of the eye from front to back can be accurately measured with lasers With light, they can bounce a beam off the back of the retina and know exactly how long the eyeball is It’s almost like sonar , but with light He knows roughly where the implant lens is going to rest when he puts it in If he knows some other dimensions of the eye and uses the front curvature as another piece of data, he can predict what power implant lens to put in
Because dry eye patients, the surface of their corneas, it’s not optically pristine; it’s a little distorted
Contact lens make this a lot worse; it can throw off his measurements This can throw off the calculation because it’s pretty simple Newtonian physics
This can throw off the calculation because it’s pretty simple Newtonian physics
The more perfect the shape of the cornea, the better that calculation is This is probably the weak link in the set of measurement they take
The length of the eye from front to back can be accurately measured with lasers
With light, they can bounce a beam off the back of the retina and know exactly how long the eyeball is It’s almost like sonar , but with light
He knows roughly where the implant lens is going to rest when he puts it in
If he knows some other dimensions of the eye and uses the front curvature as another piece of data, he can predict what power implant lens to put in
This is probably the weak link in the set of measurement they take
It’s almost like sonar , but with light

Implant technology in development

In the mid-2000s, Steven started getting involved in product design for a type of implant lens that could actually zoom focus front to back Not a bifocal or a trifocal where there are different zones of focus But a lens that could actually move or change its shape
He developed an implant that was put in humans in multiple clinical trials outside the United States and found that these could zoom focus kind of like the human lens would
But multifocal lenses, that they’ve been talking about, the bifocals, trifocal implants, they surpassed the capability of what could be achieved with the lenses that he designed Until someone comes out with a focusing implant lens that can zoom focus with the same degree of power as the bifocal and trifocal implants, it’s not going to be successful
But if there was a lens that could change its shape or change its position and zoom focus seamlessly from near to far, that would be a game-changer
Not a bifocal or a trifocal where there are different zones of focus
But a lens that could actually move or change its shape
Until someone comes out with a focusing implant lens that can zoom focus with the same degree of power as the bifocal and trifocal implants, it’s not going to be successful

“ But if we had a lens that could change its shape or change its position and zoom focus seamlessly from near to far, that would be a game-changer ” – Steven Dell

Peter asks, “ You don’t take like the lens from a young person who’s passed away and ever try to implant that into ” No, no; it doesn’t work the way a cornea does for instance [see more about cornea transplantation ]
No, no; it doesn’t work the way a cornea does for instance [see more about cornea transplantation ]

Effects of eye trauma [1:26:45]

What happens when there is trauma to the lens?

Steven notes, “ if you violate that capsule of the lens, the lens immediately becomes cloudy. ” Here’s an example about trauma; so a typical scenario is somebody is working with a weed eater, a weed whacker, or whatever And a shard of rock or glass or something goes through the cornea and embeds itself in the lens This might even be an optically unimportant part of the lens; maybe it’s off to the side But once that capsule has been pierced, inevitably, lens protein starts leaking out,and it’s no longer an immune privileged site A cataract becomes visible within days Now they need a new lens Peter asks about the cornea Sometimes they need a new cornea, but oddly enough, sometimes an object will pass through the cornea; and because it’s traveling at such a high velocity, it’s usually sterile, and it’ll go through the cornea and embed itself in the lens or the iris or wherever Some of these objects can be left alone But if the cornea has been damaged sufficiently that it’s no longer able to transmit a clear image, then it has to be replaced
Here’s an example about trauma; so a typical scenario is somebody is working with a weed eater, a weed whacker, or whatever
And a shard of rock or glass or something goes through the cornea and embeds itself in the lens This might even be an optically unimportant part of the lens; maybe it’s off to the side
But once that capsule has been pierced, inevitably, lens protein starts leaking out,and it’s no longer an immune privileged site
A cataract becomes visible within days
Now they need a new lens
Peter asks about the cornea Sometimes they need a new cornea, but oddly enough, sometimes an object will pass through the cornea; and because it’s traveling at such a high velocity, it’s usually sterile, and it’ll go through the cornea and embed itself in the lens or the iris or wherever Some of these objects can be left alone But if the cornea has been damaged sufficiently that it’s no longer able to transmit a clear image, then it has to be replaced
This might even be an optically unimportant part of the lens; maybe it’s off to the side
Sometimes they need a new cornea, but oddly enough, sometimes an object will pass through the cornea; and because it’s traveling at such a high velocity, it’s usually sterile, and it’ll go through the cornea and embed itself in the lens or the iris or wherever
Some of these objects can be left alone
But if the cornea has been damaged sufficiently that it’s no longer able to transmit a clear image, then it has to be replaced

What happens when there is trauma to the cornea?

One thing Peter remembers from surgery is to always tape the patient’s eyes shut, to avoid corneal abrasions One doesn’t want a patient’s eyelids flipping open in the middle of surgery when nobody’s paying attention, and the drape is running over the eye and scraping the cornea
Is this the biggest insult for the cornea? It’s one of the more common ones An eye that’s been left open in surgery while a patient is asleep and not blinking, that’s the extreme version of dry eye where the cornea has completely dried out Even if the cornea is not abraded, those epithelial cells would be so damaged by exposure, just by not being continuously bathed in tears that they would be severely damaged So dry eye is intimately related to corneal abrasion because these patients lack the lubrication that normally takes place to prevent that type of thing
One doesn’t want a patient’s eyelids flipping open in the middle of surgery when nobody’s paying attention, and the drape is running over the eye and scraping the cornea
It’s one of the more common ones
An eye that’s been left open in surgery while a patient is asleep and not blinking, that’s the extreme version of dry eye where the cornea has completely dried out Even if the cornea is not abraded, those epithelial cells would be so damaged by exposure, just by not being continuously bathed in tears that they would be severely damaged
So dry eye is intimately related to corneal abrasion because these patients lack the lubrication that normally takes place to prevent that type of thing
Even if the cornea is not abraded, those epithelial cells would be so damaged by exposure, just by not being continuously bathed in tears that they would be severely damaged

Corneal abrasion from ‘dry eye’: causes, treatment, and prevention strategies [1:29:00]

Dry eye is an enormous issue in our society
Think about the things that cause dry eye Lots of medications do it through anticholinergic side effects Antihistamines Hormonal influences are profound in terms of dry eye Anything that causes dry mouth can also cause dry eye Autoimmune conditions can cause dry eyes or Sjogren’s rheumatoid arthritis All of the connective tissue diseases have a dry eye component to them Perturbations of thyroid metabolism cause dry eye A lot of women suffer from dry eye mostly due to a lack of testosterone , that is probably most intimately linked to dry eye. He sees women on hormone replacement therapy that have miserable dry eye This relates to the health of the epithelial cells on the conjunctiva in the absence of testosterone, and there may be also influences on the secretion of tears from the lacrimal gland as well
Dry eye is extremely common
Lots of medications do it through anticholinergic side effects
Antihistamines
Hormonal influences are profound in terms of dry eye
Anything that causes dry mouth can also cause dry eye
Autoimmune conditions can cause dry eyes or Sjogren’s rheumatoid arthritis
All of the connective tissue diseases have a dry eye component to them
Perturbations of thyroid metabolism cause dry eye
A lot of women suffer from dry eye mostly due to a lack of testosterone , that is probably most intimately linked to dry eye. He sees women on hormone replacement therapy that have miserable dry eye This relates to the health of the epithelial cells on the conjunctiva in the absence of testosterone, and there may be also influences on the secretion of tears from the lacrimal gland as well
He sees women on hormone replacement therapy that have miserable dry eye
This relates to the health of the epithelial cells on the conjunctiva in the absence of testosterone, and there may be also influences on the secretion of tears from the lacrimal gland as well

Treatment for dry eye

Peter asks, “ What type of eye drops should we be using? How do we apply them? ”
It depends on the type of dry eye One thinks of tears as just saltwater, but that’s really not what it is It’s really an emulsion of lipids and mucin and all sorts of immune modulators and antibodies and all sorts of things in this soup Some of it is just what is referred to as the aqueous component of tears, really just the saltwater But the sebaceous glands that are in the eyelids are called meibomian glands (where the lashes come out of the skin), the secretions of those meibomian glands can become dysfunctional And that means that the tears have a hard time gliding over the surface of the cornea; and that can lead to dry eye So all sorts of things that cause meibomian gland dysfunction Some of that relates to diet; some people believe that a diet high in saturated fats is more likely to cause meibomian gland dysfunction Certainly colder weather affects these glands, just like the sebaceous glands in the skin, they respond better to sunlight, to heat In a cold environment the meibomian glands can become plugged up and bacteria can build up along the eyelid margin causing inflammation And when there’s inflammation, the lacrimal gland shuts down even more
One thinks of tears as just saltwater, but that’s really not what it is It’s really an emulsion of lipids and mucin and all sorts of immune modulators and antibodies and all sorts of things in this soup Some of it is just what is referred to as the aqueous component of tears, really just the saltwater
But the sebaceous glands that are in the eyelids are called meibomian glands (where the lashes come out of the skin), the secretions of those meibomian glands can become dysfunctional And that means that the tears have a hard time gliding over the surface of the cornea; and that can lead to dry eye So all sorts of things that cause meibomian gland dysfunction Some of that relates to diet; some people believe that a diet high in saturated fats is more likely to cause meibomian gland dysfunction Certainly colder weather affects these glands, just like the sebaceous glands in the skin, they respond better to sunlight, to heat In a cold environment the meibomian glands can become plugged up and bacteria can build up along the eyelid margin causing inflammation And when there’s inflammation, the lacrimal gland shuts down even more
It’s really an emulsion of lipids and mucin and all sorts of immune modulators and antibodies and all sorts of things in this soup
Some of it is just what is referred to as the aqueous component of tears, really just the saltwater
And that means that the tears have a hard time gliding over the surface of the cornea; and that can lead to dry eye
So all sorts of things that cause meibomian gland dysfunction Some of that relates to diet; some people believe that a diet high in saturated fats is more likely to cause meibomian gland dysfunction Certainly colder weather affects these glands, just like the sebaceous glands in the skin, they respond better to sunlight, to heat In a cold environment the meibomian glands can become plugged up and bacteria can build up along the eyelid margin causing inflammation And when there’s inflammation, the lacrimal gland shuts down even more
Some of that relates to diet; some people believe that a diet high in saturated fats is more likely to cause meibomian gland dysfunction
Certainly colder weather affects these glands, just like the sebaceous glands in the skin, they respond better to sunlight, to heat
In a cold environment the meibomian glands can become plugged up and bacteria can build up along the eyelid margin causing inflammation
And when there’s inflammation, the lacrimal gland shuts down even more

Eye drops

Peter notes, “ when I think about eyedrops, I think about sort of the dropper that you try to get in your eye, and you can never get it, at least I can never get it in my eye because I end up blinking all the time. So then you try and drop it into the corner ”
But he’s also seen the mist applicators
What are the different ways eyedrops can be applied?
Eye drops work pretty well for most people; most artificial tears come in the form of an eye drop
There are some mist sprays, believe it or not, one is a hypochlorous acid compound that is sprayed on the lids; and it sort of migrates into the eye This actually is very good for reducing the bacterial counts at the lid margin, which is part of that inflammation cycle that is so critical in dry eye
The eye drops do need to get on the eyeball
Eye drops are just one of just a whole bunch of strategies used for treating dry eye There’s a very significant benefit from supplementing with omega-3 fatty acids, especially high doses of omega-3 fatty acids and certain types of omega-6 fatty acids such as: GLA (gamma-linolenic acid) ; that’s what you’d find in black current seed oil, borage oil, or evening primrose oil There was a very large randomized clinical trial looking at omega-3 supplementation in pretty high doses, 3 grams of EPA and DHA Published in Opthalmology in 2020, Effects of Omega-3 Supplementation on Exploratory Outcomes in the DREAM Study And the placebo arm used olive oil, which is presumed not to have a benefit in dry eye It showed no superiority of omega-3 compared to olive oil However, there has been a lot of criticism of this study; it was called the DREAM study This study was conducted by the National Eye Institute Participants were able to continue to use whatever eye drops they used to help with dry eye It turns out that if you bring people into the eye doctor four times a year, everybody gets better; their compliance with artificial tears gets better But he has a very strong clinical impression that omega-3s in high doses do help with dry eye; primarily from an anti-inflammatory standpoint
This actually is very good for reducing the bacterial counts at the lid margin, which is part of that inflammation cycle that is so critical in dry eye
There’s a very significant benefit from supplementing with omega-3 fatty acids, especially high doses of omega-3 fatty acids and certain types of omega-6 fatty acids such as: GLA (gamma-linolenic acid) ; that’s what you’d find in black current seed oil, borage oil, or evening primrose oil
There was a very large randomized clinical trial looking at omega-3 supplementation in pretty high doses, 3 grams of EPA and DHA Published in Opthalmology in 2020, Effects of Omega-3 Supplementation on Exploratory Outcomes in the DREAM Study And the placebo arm used olive oil, which is presumed not to have a benefit in dry eye It showed no superiority of omega-3 compared to olive oil However, there has been a lot of criticism of this study; it was called the DREAM study This study was conducted by the National Eye Institute Participants were able to continue to use whatever eye drops they used to help with dry eye It turns out that if you bring people into the eye doctor four times a year, everybody gets better; their compliance with artificial tears gets better
But he has a very strong clinical impression that omega-3s in high doses do help with dry eye; primarily from an anti-inflammatory standpoint
GLA (gamma-linolenic acid) ; that’s what you’d find in black current seed oil, borage oil, or evening primrose oil
Published in Opthalmology in 2020, Effects of Omega-3 Supplementation on Exploratory Outcomes in the DREAM Study
And the placebo arm used olive oil, which is presumed not to have a benefit in dry eye
It showed no superiority of omega-3 compared to olive oil
However, there has been a lot of criticism of this study; it was called the DREAM study This study was conducted by the National Eye Institute Participants were able to continue to use whatever eye drops they used to help with dry eye It turns out that if you bring people into the eye doctor four times a year, everybody gets better; their compliance with artificial tears gets better
This study was conducted by the National Eye Institute
Participants were able to continue to use whatever eye drops they used to help with dry eye
It turns out that if you bring people into the eye doctor four times a year, everybody gets better; their compliance with artificial tears gets better

Sunglasses for eye protection [1:35:00]

Peter has some friends who are so fanatical about the importance of light that they never wear sunglasses He thinks light is great but likes wearing sunglasses because there’s a part of him that’s sort of afraid that too much UV light is damaging What is a good balance?
There’s a dose-related phenomenon here— too much light is bad; too little light is bad
He tends to recommend sunglasses for his patients for a number of reasons: 1) The most common site of skin cancer is the lower lid There are lots of basal cell and squamous cell carcinomas , and sunglasses certainly reduce the incidents of that 2) Consider photoaging of the lens itself; It’s not a bad thing to delay the onset of cataract 3) Retina macular degeneration ; there’s pretty clear evidence that UV exposure, particularly of the magnitude that one can get outside, is associated with an elevated risk of age-related macular degeneration Peter asks if this is seen in hunter-gatherers who have otherwise amazing habits and therefore tend to be relatively privileged from optical pathology The confounding variable there is that Northern European ancestry is a risk factor for macular degeneration, probably because of the lack of pigment Pigment in the eye is protecting that very vulnerable vascularized component of the back of the eye The darker one’s eye, the more protected they are in the same way that skin is more protected with more melanin So light-eyed patients have more light getting in from the front of the eye; their iris literally blocks less light hitting the lens and the retina has less pigment behind it For light-eyed patients, the vascular supply to the retina is more exposed to UV light, and that’s the way it’s evolved because they’ve been in environments that don’t have as much light available But if one lives near the equator or one’s ancestry is from that area, then they’re going to have more pigment from an evolutionary standpoint
If the goal is longevity or the postponement of senescence, certainly ocular senescence, he thinks it makes sense to protect one’s eyes from UV light
If he’s outside and is vision is better with sunglasses then he’s going to wear them; if it’s not worse with sunglasses then he’s going to wear them He’s doesn’t wear them at night
Peter relates this to sunscreen, one is still susceptible to sunburn on a cloudy, overcast day
He asks if it’s still a good idea to wear sunglasses even when it’s cloudy Yes
This kind of came up during a recent eclipse because people were saying, “ Okay, I’ll look at the eclipse; I’ll just use sunglasses .” Well, that’s actually much, much worse because this increases the aperture of one’s pupil Because everything is dim, but it’s letting through all this very damaging light
He thinks light is great but likes wearing sunglasses because there’s a part of him that’s sort of afraid that too much UV light is damaging
What is a good balance?
1) The most common site of skin cancer is the lower lid There are lots of basal cell and squamous cell carcinomas , and sunglasses certainly reduce the incidents of that
2) Consider photoaging of the lens itself; It’s not a bad thing to delay the onset of cataract
3) Retina macular degeneration ; there’s pretty clear evidence that UV exposure, particularly of the magnitude that one can get outside, is associated with an elevated risk of age-related macular degeneration Peter asks if this is seen in hunter-gatherers who have otherwise amazing habits and therefore tend to be relatively privileged from optical pathology The confounding variable there is that Northern European ancestry is a risk factor for macular degeneration, probably because of the lack of pigment Pigment in the eye is protecting that very vulnerable vascularized component of the back of the eye The darker one’s eye, the more protected they are in the same way that skin is more protected with more melanin So light-eyed patients have more light getting in from the front of the eye; their iris literally blocks less light hitting the lens and the retina has less pigment behind it For light-eyed patients, the vascular supply to the retina is more exposed to UV light, and that’s the way it’s evolved because they’ve been in environments that don’t have as much light available But if one lives near the equator or one’s ancestry is from that area, then they’re going to have more pigment from an evolutionary standpoint
There are lots of basal cell and squamous cell carcinomas , and sunglasses certainly reduce the incidents of that
Peter asks if this is seen in hunter-gatherers who have otherwise amazing habits and therefore tend to be relatively privileged from optical pathology
The confounding variable there is that Northern European ancestry is a risk factor for macular degeneration, probably because of the lack of pigment Pigment in the eye is protecting that very vulnerable vascularized component of the back of the eye The darker one’s eye, the more protected they are in the same way that skin is more protected with more melanin So light-eyed patients have more light getting in from the front of the eye; their iris literally blocks less light hitting the lens and the retina has less pigment behind it For light-eyed patients, the vascular supply to the retina is more exposed to UV light, and that’s the way it’s evolved because they’ve been in environments that don’t have as much light available But if one lives near the equator or one’s ancestry is from that area, then they’re going to have more pigment from an evolutionary standpoint
Pigment in the eye is protecting that very vulnerable vascularized component of the back of the eye
The darker one’s eye, the more protected they are in the same way that skin is more protected with more melanin
So light-eyed patients have more light getting in from the front of the eye; their iris literally blocks less light hitting the lens and the retina has less pigment behind it
For light-eyed patients, the vascular supply to the retina is more exposed to UV light, and that’s the way it’s evolved because they’ve been in environments that don’t have as much light available
But if one lives near the equator or one’s ancestry is from that area, then they’re going to have more pigment from an evolutionary standpoint
He’s doesn’t wear them at night
Yes
Well, that’s actually much, much worse because this increases the aperture of one’s pupil
Because everything is dim, but it’s letting through all this very damaging light

“ No amount of sunglasses could block a straight shot looking at the sun ” – Steven Dell

Polarized sunglasses

What about polarized lenses?
A polarized lens is a lens that has a bunch of lines drawn in it, all in the same direction, so that some of the light is blocked In one meridian all the light effectively is let through But perpendicular to that, none of the light gets through
Polarized lenses have some pluses and minuses One of the big minuses is the difficulty in viewing a lot of the displays in cars now One gets this really messed up cross polarized effect where the light coming off of the screen is polarized When one looks at it through polarized glasses, with a certain tilt of the head, it gets brighter and at other orientations it can’t be seen By the same token, he’s noticed that many of the car windows, he don’t know if it’s the windshield or the side windows, would produce these very weird effects when he tilts his head because of the cross polarized effect Essentially this happens where there are 2 different polarized filters and it’s letting through variable amounts of light depending upon the orientation of your head and your eye, and the spectacles
Peter has found himself more comfortable in non-polarized lenses, unless he’s on water The issue there is that the light bouncing off the water, or theoretically a highway A lot of it is polarized in one direction That’s the rationale behind polarized lenses And for seeing a fish; if one is a fly fisherman, that’s helpful
In terms of polarization, there’s no evidence that polarization versus non-polarization in sunglasses helps
It’s really the UV filter that is helpful in terms of protection of eye health One could wear clear spectacles, as long as they had UV protection, and still achieve the benefit of sunglasses It’s not the tint that protects the eyes; it’s the ultraviolet protection The same is true for car windows
Car and truck windows do let some UV light in In North America, truck drivers see more UV damage to the left side of their face than the right side of their face by far And in the UK, it’s exactly the opposite
In one meridian all the light effectively is let through
But perpendicular to that, none of the light gets through
One of the big minuses is the difficulty in viewing a lot of the displays in cars now One gets this really messed up cross polarized effect where the light coming off of the screen is polarized When one looks at it through polarized glasses, with a certain tilt of the head, it gets brighter and at other orientations it can’t be seen
By the same token, he’s noticed that many of the car windows, he don’t know if it’s the windshield or the side windows, would produce these very weird effects when he tilts his head because of the cross polarized effect
Essentially this happens where there are 2 different polarized filters and it’s letting through variable amounts of light depending upon the orientation of your head and your eye, and the spectacles
One gets this really messed up cross polarized effect where the light coming off of the screen is polarized
When one looks at it through polarized glasses, with a certain tilt of the head, it gets brighter and at other orientations it can’t be seen
The issue there is that the light bouncing off the water, or theoretically a highway A lot of it is polarized in one direction That’s the rationale behind polarized lenses And for seeing a fish; if one is a fly fisherman, that’s helpful
A lot of it is polarized in one direction
That’s the rationale behind polarized lenses
And for seeing a fish; if one is a fly fisherman, that’s helpful
One could wear clear spectacles, as long as they had UV protection, and still achieve the benefit of sunglasses
It’s not the tint that protects the eyes; it’s the ultraviolet protection
The same is true for car windows
In North America, truck drivers see more UV damage to the left side of their face than the right side of their face by far
And in the UK, it’s exactly the opposite

Solutions to correct nearsightedness [1:42:00]

Which is better, glasses or contacts?

When a nearsighted person comes in, they can correct this with glasses or contacts, Peter asks “ Do you nudge people one way or the other? ” Peter recalls he wore glasses for the first 4 years that he needed corrective lenses Then by med school he was wearing contacts But by residency he went back to glasses because he couldn’t be predictable about when he was going to put them in Since then he’s used contacts
Steven notes that when residents, fellows, or whatever see the optometrist and are asked “ When did you last have your contacts out? ” They’re like, “ I think it was June 30th, right before my internship started four months ago. ” Residents are notoriously bad about their own health hygiene, because they’re so busy
But to answer the question more directly, Steven doesn’t really see patients for regular eye exams; the people he sees are seeking surgery
Peter recalls he wore glasses for the first 4 years that he needed corrective lenses
Then by med school he was wearing contacts
But by residency he went back to glasses because he couldn’t be predictable about when he was going to put them in
Since then he’s used contacts
They’re like, “ I think it was June 30th, right before my internship started four months ago. ”
Residents are notoriously bad about their own health hygiene, because they’re so busy

“ The safest thing you can do is wear spectacles for sure ” – Steven Dell

So spectacles and glasses are synonymous; that’s the safest option They’re going to work every time and there’s essentially no risk associated with them
There’s a big debate about what the next safest thing is Is it contact lens wear for 10 years, where one might be susceptible to infection, or is it laser vision correction? He tends to say, “ If you’re doing fine with spectacles or contact lenses, do that. ” Peter was hoping he would say, “ Get laser eye surgery ” because part of him wants to get rid of contacts once and for all But after a bunch of questions, Steven’s conclusion was, “ These don’t seem to be an inconvenience for you. You’ve never once had an eye infection. You tolerate them really well. They don’t seem to bug you. “ If he was to correct Peter’s distance vision with laser surgery and set both of his eyes for distance, he would lose that near vision Until maybe he gets cataracts fixed; that’s a whole other story
They’re going to work every time and there’s essentially no risk associated with them
Is it contact lens wear for 10 years, where one might be susceptible to infection, or is it laser vision correction?
He tends to say, “ If you’re doing fine with spectacles or contact lenses, do that. ”
Peter was hoping he would say, “ Get laser eye surgery ” because part of him wants to get rid of contacts once and for all
But after a bunch of questions, Steven’s conclusion was, “ These don’t seem to be an inconvenience for you. You’ve never once had an eye infection. You tolerate them really well. They don’t seem to bug you. “
If he was to correct Peter’s distance vision with laser surgery and set both of his eyes for distance, he would lose that near vision Until maybe he gets cataracts fixed; that’s a whole other story
Until maybe he gets cataracts fixed; that’s a whole other story

Laser eye surgery—photorefractive keratectomy (PRK) [1:45:45]

The first laser eye surgery

Everybody listing to this has heard of LASIK (laser-assisted in situ keratomileusis)
Most people probably haven’t heard of PRK (photorefractive keratectomy), which came alone first
The approvals for PRK and LASIK were in the mid ’90s, 1995, 1996 The first procedure was PRK and it was done in New Orleans, and he had happened to be in training there at the time This was performed by a physician called Marguerite McDonald She did the very first treatment on a human eye The way this came about was an engineer at IBM realizes that excimer lasers , used to etch microchips, could also be used to change the curvature or make cuts in human tissue And because of the nature of this ultraviolet laser, there was essentially no bystander trauma to the adjacent tissue, so the tissue could be etched or cut Further, because it generated no heat, there was typically no immune response generated, so these incisions would heal without scarring He remembers vividly looking at the very first patients to undergo PRK in an FDA clinical trial, and was astonished that one could look at them under a microscope and not detect that surgery had been done
The first procedure was PRK and it was done in New Orleans, and he had happened to be in training there at the time
This was performed by a physician called Marguerite McDonald She did the very first treatment on a human eye
The way this came about was an engineer at IBM realizes that excimer lasers , used to etch microchips, could also be used to change the curvature or make cuts in human tissue And because of the nature of this ultraviolet laser, there was essentially no bystander trauma to the adjacent tissue, so the tissue could be etched or cut Further, because it generated no heat, there was typically no immune response generated, so these incisions would heal without scarring
He remembers vividly looking at the very first patients to undergo PRK in an FDA clinical trial, and was astonished that one could look at them under a microscope and not detect that surgery had been done
She did the very first treatment on a human eye
And because of the nature of this ultraviolet laser, there was essentially no bystander trauma to the adjacent tissue, so the tissue could be etched or cut
Further, because it generated no heat, there was typically no immune response generated, so these incisions would heal without scarring

“ That was really a revelation for me, where I just saw these eyes that looked like normal eyes, and the only difference was the patients could see ” – Steven Dell

So the first eyes were treated in ’89 (as part of a clinical trial) and that led to FDA approval in ’95

How PRK works

Consider the cornea again like the glass on a watch, the thing a contact lens would sit on And let’s say that the person is nearsighted; their cornea is a little bit too steep to focus the light perfectly on their retina Or the eyeball is a little too long; probably a little of both The length of the eye cannot be changed; this was discussed as being somewhat malleable during development The corneal shape doesn’t seem to change that much throughout life It’s the length of the eye that changes, unless there’s a pathological condition that changes the cornea The cornea is about half a millimeter thick (500 microns) Since the length of the eye cannot be changed; what can be changed is the curvature of the front of the eye The curvature doesn’t have to change that much; think about how thin a contact lens is Only a little curvature needs to change in order to focus the light on the retina
Take for example a person who’s diopter is -1; they have a very minimal degree of nearsightedness Their cornea is less potent in bending light than the -10 person is That -10 means their eye is 10 units too strong, and the power of the eye needs to be reduced
To fix their vision with a contact lens, the contact hast to be flatter than their eyeball They need a larger radius sub-curvature or a flatter eye The solution is to build up the outside of the lens
It’s even easier to explain with laser vision correction
Consider a crude analogy, which is that the cornea is made out of wood and he has some sandpaper
He can sand down the center of the wooden cornea and make it flatter Now it’s less powerful in bending the light, and the light can be focused on the retina
So in the -1 example, he would remove about 20 microns of tissue; that’s not a lot Compare this to a human hair, it’s about 50 microns So this is less than half of one human hair’s thickness
PRK does this with an excimer laser on the very front part of the cornea
The very front coating of the cornea is called the epithelium It’s a very thin layer, about 50, 55 microns thick; it’s got a basement membrane 1) He removes that layer of cells with a solution of alcohol eye drops; it just sloughs right off, and it grows back in the same configuration He anesthetizes the eye first 2) Then he uses a very carefully calibrated laser to change the shape of the cornea The laser is effectively perpendicular to the cornea The patient is laying down flat on their back
Peter asks if the people are sedated Steven gives Valium simply because it is intimidating; but the procedure only takes a minute
Peter’s fear is that his desire to blink would be so overwhelming that he would break the little eye barrier or end up moving his head and the doctor would zap the wrong part of his eye and he would be blind Steven comments, “ That’s everyone’s fear. It turns out Valium is undefeated. It’s just a question of how much. ”
A lot of patients fear that they’ll do something to goof up the surgery and there are a number of reasons why that really can’t happen
And let’s say that the person is nearsighted; their cornea is a little bit too steep to focus the light perfectly on their retina Or the eyeball is a little too long; probably a little of both
The length of the eye cannot be changed; this was discussed as being somewhat malleable during development
The corneal shape doesn’t seem to change that much throughout life
It’s the length of the eye that changes, unless there’s a pathological condition that changes the cornea
The cornea is about half a millimeter thick (500 microns)
Since the length of the eye cannot be changed; what can be changed is the curvature of the front of the eye The curvature doesn’t have to change that much; think about how thin a contact lens is
Only a little curvature needs to change in order to focus the light on the retina
Or the eyeball is a little too long; probably a little of both
The curvature doesn’t have to change that much; think about how thin a contact lens is
Their cornea is less potent in bending light than the -10 person is
That -10 means their eye is 10 units too strong, and the power of the eye needs to be reduced
They need a larger radius sub-curvature or a flatter eye
The solution is to build up the outside of the lens
Now it’s less powerful in bending the light, and the light can be focused on the retina
Compare this to a human hair, it’s about 50 microns
So this is less than half of one human hair’s thickness
It’s a very thin layer, about 50, 55 microns thick; it’s got a basement membrane
1) He removes that layer of cells with a solution of alcohol eye drops; it just sloughs right off, and it grows back in the same configuration He anesthetizes the eye first
2) Then he uses a very carefully calibrated laser to change the shape of the cornea The laser is effectively perpendicular to the cornea The patient is laying down flat on their back
He anesthetizes the eye first
The laser is effectively perpendicular to the cornea
The patient is laying down flat on their back
Steven gives Valium simply because it is intimidating; but the procedure only takes a minute
Steven comments, “ That’s everyone’s fear. It turns out Valium is undefeated. It’s just a question of how much. ”

Details of the PRK procedure

Long before this patient ever laid down on this gurney to have this laser treatment done, their eye was digitally mapped using what is referred to as a wavefront sensing device So think about this, a very narrow beam of light is sent in with a laser and how it bounces back from the cornea is determined It bounces back in a distorted fashion An ideal ray of light in, or multiple rays of light are sent in, and they bounce back in a distorted fashion The amount of that distortion allows a map to be created It’s much more than a topographical map It’s the entire optical pathway of the eye from the retina to the back, all the way to the back and front The entire distortion pathway is visualized There’s more than one way to do this: 1) There is a topography-based way to do this as well, which is very effective 2) The one he’s describing is sort of the easiest one to think of A known uniform beam of light is sent in and he looks at how it bounces back from the back of the eye That reveals what are the distortions present in this eye; how much nearsightedness, farsightedness…
Diagnostically, this is part of the workup for laser vision correction They look at how a particular eyeball distorts light as it goes through the optical pathway This technology was developed for telescopes that have to contend with atmospheric distortion, like the Keck They send up a diagnostic laser into the atmosphere and the distortion that that laser is encountering is adjusted for in real time with a deformable mirror, a very thin mirror, and that allows them to essentially correct for the distortions of the atmosphere in real time And those are constantly changing In the eye they have the benefit of not having to deal with real time, evolving distortion, but he can take a snapshot of what the distortions are in the eyeball Part of that involves the ability to track the eye They have to lock onto, and register the eye with the equipment The laser can track any movement one makes far more rapidly than it is possible to move the eye It doesn’t matter if the patient’s eyes are moving during this diagnostic because the laser is moving He does coach them to, “ Hey, look at the flashing light ” but that’s really just to keep them in the ballpark of where the tracker can lock onto them
The fear of the patient, “ I’m going to mess it up. ” is not a ridiculous fear; it’s universal
Steven tells patients, “ Hey, I’m not going to let you do anything to mess this up ”
The laser will not fire unless the patient is within its range of tracking, and the laser will move faster than the patient can move
So PRK is changing the shape of the eye by vaporizing the tissue It’s a laser that’s scanning around the cornea where it does a little treatment here and there Thermally one doesn’t want to do another shot right next to the previous one, so it moves over to another area to let the tissue cool down for a few milliseconds So the laser dances around
This takes anywhere from 15 seconds to 2 minutes The worse the prescription is, the longer it takes So a -10 would take a minute or so It depends on the laser and the overall treatment size
This fixes the astigmatism and all the little distortions
He measures all the little optical distortions, the coma and trefoil (terms optical physicists are very familiar with), and does his best to eliminate them with laser vision correction
For PRK this takes 2-3 minutes, plus the Valium time The patient takes Valium a half an hour before; it works pretty quickly when they chew it
Comparing PRK and LASIK— 30 days after the procedure, the results are indistinguishable But the LASIK patients get there way quicker
So think about this, a very narrow beam of light is sent in with a laser and how it bounces back from the cornea is determined
It bounces back in a distorted fashion
An ideal ray of light in, or multiple rays of light are sent in, and they bounce back in a distorted fashion
The amount of that distortion allows a map to be created
It’s much more than a topographical map
It’s the entire optical pathway of the eye from the retina to the back, all the way to the back and front
The entire distortion pathway is visualized There’s more than one way to do this: 1) There is a topography-based way to do this as well, which is very effective 2) The one he’s describing is sort of the easiest one to think of A known uniform beam of light is sent in and he looks at how it bounces back from the back of the eye That reveals what are the distortions present in this eye; how much nearsightedness, farsightedness…
There’s more than one way to do this:
1) There is a topography-based way to do this as well, which is very effective
2) The one he’s describing is sort of the easiest one to think of A known uniform beam of light is sent in and he looks at how it bounces back from the back of the eye That reveals what are the distortions present in this eye; how much nearsightedness, farsightedness…
A known uniform beam of light is sent in and he looks at how it bounces back from the back of the eye
That reveals what are the distortions present in this eye; how much nearsightedness, farsightedness…
They look at how a particular eyeball distorts light as it goes through the optical pathway
This technology was developed for telescopes that have to contend with atmospheric distortion, like the Keck They send up a diagnostic laser into the atmosphere and the distortion that that laser is encountering is adjusted for in real time with a deformable mirror, a very thin mirror, and that allows them to essentially correct for the distortions of the atmosphere in real time And those are constantly changing
In the eye they have the benefit of not having to deal with real time, evolving distortion, but he can take a snapshot of what the distortions are in the eyeball Part of that involves the ability to track the eye They have to lock onto, and register the eye with the equipment The laser can track any movement one makes far more rapidly than it is possible to move the eye
It doesn’t matter if the patient’s eyes are moving during this diagnostic because the laser is moving
He does coach them to, “ Hey, look at the flashing light ” but that’s really just to keep them in the ballpark of where the tracker can lock onto them
They send up a diagnostic laser into the atmosphere and the distortion that that laser is encountering is adjusted for in real time with a deformable mirror, a very thin mirror, and that allows them to essentially correct for the distortions of the atmosphere in real time
And those are constantly changing
Part of that involves the ability to track the eye
They have to lock onto, and register the eye with the equipment
The laser can track any movement one makes far more rapidly than it is possible to move the eye
It’s a laser that’s scanning around the cornea where it does a little treatment here and there
Thermally one doesn’t want to do another shot right next to the previous one, so it moves over to another area to let the tissue cool down for a few milliseconds So the laser dances around
So the laser dances around
The worse the prescription is, the longer it takes
So a -10 would take a minute or so
It depends on the laser and the overall treatment size
The patient takes Valium a half an hour before; it works pretty quickly when they chew it
But the LASIK patients get there way quicker

PRK recovery

With PRK the epithelium is removed so now there is a 7-8 mm diameter area of the central cornea that has no epithelium It has to grow back That’s like having a big corneal abrasion
Luckily there are drops that can reduce the feeling of the foreign body sensation dramatically
They put a contact lens over the eye; it acts like a band-aid It’s really like a regular soft contact lens
Then the epithelium begins to heal from the outside in This takes about 4 days But here’s the thing, if one has a cut on their arm, it would heal over but they could still be able to detect where the cut was because those cells have not fully remodeled themselves After 4 days the contact lens is removed, but the vision is still not perfect yet because those cells have to reorient themselves like a bunch of orderly bricks in a brick wall When the cells first cover that defect, it’s a very thin sort of disorganized layer of cells that have accomplished their mission of sealing the defect and preventing one from being susceptible to infection This is their job to quickly cover the defect But then the body can turn its attention to reorganizing those cells in a model
Peter asks if they do one eye at a time
Not with PRK or LASIK; no
Typically they do both eyes on the same day because the level of vision is probably about 20/30 or 20/40 within a day or 2
The patient recovers vision pretty quickly, but that last little bit takes several days So they could probably drive 2-3 days later; but they wouldn’t have 20/20 vision at that point
It has to grow back
That’s like having a big corneal abrasion
It’s really like a regular soft contact lens
This takes about 4 days
But here’s the thing, if one has a cut on their arm, it would heal over but they could still be able to detect where the cut was because those cells have not fully remodeled themselves
After 4 days the contact lens is removed, but the vision is still not perfect yet because those cells have to reorient themselves like a bunch of orderly bricks in a brick wall
When the cells first cover that defect, it’s a very thin sort of disorganized layer of cells that have accomplished their mission of sealing the defect and preventing one from being susceptible to infection This is their job to quickly cover the defect
But then the body can turn its attention to reorganizing those cells in a model
This is their job to quickly cover the defect
So they could probably drive 2-3 days later; but they wouldn’t have 20/20 vision at that point

Laser eye surgery—LASIK [2:02:00]

How LASIK works

LASIK is different from PRK because the epithelium is not shaved off; instead a flap is cut
The new shape of the cornea is determined by how much tissue is removed when the flap comes back
The same laser is used in LASIK and PRK
Instead of using the laser on the surface of the eye, a step is added before that
He creates a flap in the cornea using a different type of laser He uses a femtosecond laser to create about a 100 micron flap; so now he can work under the epithelium He’s taken about 20% of the cornea up
Think of the analogy used earlier of sanding a wooden eye; now think of the cornea as a book In PRK he removes the first 10 pages of the book In LASIK he opens the book to page 100 and takes out pages 100-110; then he closes the book
He uses a femtosecond laser to create about a 100 micron flap; so now he can work under the epithelium
He’s taken about 20% of the cornea up
In PRK he removes the first 10 pages of the book
In LASIK he opens the book to page 100 and takes out pages 100-110; then he closes the book

“ The beauty of LASIK is that because the tissue removal is sequestered under that flap, the body doesn’t perceive that anything has been done ” – Steven Dell

It’s very typical for patients who have LASIK to be 20/20 the next morning That’s the appeal of this procedure
Peter asks if LASIK was developed after PRK as a way to get around the healing process of PRK Yes, the way it was developed was sort of a technological race Part if this was the pursuit of more rapid visual recovery
About 80-85% of the corrective eye surgery in the US today is LASIK There another procedure called SMILE which has a very small, but perhaps growing segment of the market PRK still has a significant chunk of the market
That’s the appeal of this procedure
Yes, the way it was developed was sort of a technological race Part if this was the pursuit of more rapid visual recovery
Part if this was the pursuit of more rapid visual recovery
There another procedure called SMILE which has a very small, but perhaps growing segment of the market
PRK still has a significant chunk of the market

Recovery from LASIK

Peter asks if the risks are different in LASIK versus PRK The risk of infection with LASIK is lower because the epithelium is not taken away But another step is introduced in the procedure, the flap; if the flap is not performed correctly, it can lead to problems There is more dry eye following LASIK compared to PRK Creating the flap temporarily severs some of the nerves that send the signal from the front of the eye to the lacrimal gland , which secretes tears Those nerves typically regrow back and one reestablishes that feedback mechanism Some people have data to show that dry eye is equal in patients receiving LASIK and PRK, but he thinks there is more dry eye following LASIK; it’s controversial Some patients have dry eye for really long periods of time after both procedures The majority of patients are back to their baseline in about 60 to 90 days
The risk of infection with LASIK is lower because the epithelium is not taken away
But another step is introduced in the procedure, the flap; if the flap is not performed correctly, it can lead to problems
There is more dry eye following LASIK compared to PRK Creating the flap temporarily severs some of the nerves that send the signal from the front of the eye to the lacrimal gland , which secretes tears Those nerves typically regrow back and one reestablishes that feedback mechanism Some people have data to show that dry eye is equal in patients receiving LASIK and PRK, but he thinks there is more dry eye following LASIK; it’s controversial Some patients have dry eye for really long periods of time after both procedures The majority of patients are back to their baseline in about 60 to 90 days
Creating the flap temporarily severs some of the nerves that send the signal from the front of the eye to the lacrimal gland , which secretes tears
Those nerves typically regrow back and one reestablishes that feedback mechanism
Some people have data to show that dry eye is equal in patients receiving LASIK and PRK, but he thinks there is more dry eye following LASIK; it’s controversial
Some patients have dry eye for really long periods of time after both procedures
The majority of patients are back to their baseline in about 60 to 90 days

Night vision after corrective laser eye surgery

Peter asks about night vision or low-light vision
In the early days of LASIK and PRK, the weakest part of vision was night vision
This was due to the shape of the treatment that was used; and the diameter that was treated was limited
They couldn’t really treat the peripheral part of the cornea that comes into play when the pupils gets big
When they are treating a central part of the cornea that is smaller than a big pupil at night, one is going to see halos from that untreated peripheral part of the cornea
From the ’90s to now, the treatment beam patterns have changed to address that issue and to treat that peripheral cornea differently
So now, night vision complaints are pretty unusual with laser vision correction

Cost of laser corrective eye surgery

Peter asks if there is a difference in the cost of LASIK and PRK Steven charges the same The added step of LASIK adds some cost But PRK has more postoperative care; this requires more visits So he prices them the same
The cost has stayed pretty stable over the last 20 years; it’s a couple thousand dollars per eye
Steven charges the same
The added step of LASIK adds some cost
But PRK has more postoperative care; this requires more visits
So he prices them the same

Contraindications for LASIK and/or PRK

Peter asks, “ What are the exclusion criteria, who is not a candidate for either one? ”
There are conditions of the cornea where the cornea is biomechanically unstable, where the cornea actually has a tendency to bow forward in a pathological state And that means that the cornea is essentially a moving target So further biomechanically weakening of the cornea makes no sense, and either procedure would do that
There are patients who have irregularities in their astigmatism that cannot be measured or corrected with any laser vision correction
There are patients that have certain autoimmune diseases that maybe render them as poor candidates for laser vision correction Based on the risk of healing or even just the overall health of the eye
People who have other eye diseases like cataract, or maybe glaucoma, or retinal pathology are not good candidates for laser vision correction
These operations are typically performed on healthy eyes
And that means that the cornea is essentially a moving target
So further biomechanically weakening of the cornea makes no sense, and either procedure would do that
Based on the risk of healing or even just the overall health of the eye

When is PRK the best option?

Given the differences explained, Peter asks, “ why are 15% of people still opting for PRK? ”
There are certain patients where PRK is a far better option
He talked about how this procedure is akin to removing pages from a book What if a really deep treatment is needed and the book is sort of thin to start out with? Maybe it’s better to begin on page 1 than to begin page 100
Sometimes the thickness of the cornea will dictate this
Sometimes it might be related to someone with preexisting dry eye, and he thinks PRK may be a little better
There used to be some restrictions in branches of the military These pretty much all went away; all aviators and pilots can now have LASIK or PRK In fact, the military is one of the largest providers of laser vision correction now in the United States
Peter asks if it’s a given that someone will have 20/20 vision after laser corrective surgery Yes, the way lasers are built today, this is typically the case Patients will be 20/20 or better
If the patient is taken to 20/15 and they have presbyopia to begin with, does it get any worse or is it that they notice it all the time because they never take their glasses off so to speak and see the difference? If the surgery nails their prescription perfectly, their distance vision will be phenomenal and their near vision will be based on their age So if they’re 50 years old, they are probably going to need some near correction, some spectacles for reading If their in their early to mid 40’s, they may not need glasses for close up
What if a really deep treatment is needed and the book is sort of thin to start out with?
Maybe it’s better to begin on page 1 than to begin page 100
These pretty much all went away; all aviators and pilots can now have LASIK or PRK
In fact, the military is one of the largest providers of laser vision correction now in the United States
Yes, the way lasers are built today, this is typically the case
Patients will be 20/20 or better
If the surgery nails their prescription perfectly, their distance vision will be phenomenal and their near vision will be based on their age
So if they’re 50 years old, they are probably going to need some near correction, some spectacles for reading
If their in their early to mid 40’s, they may not need glasses for close up

Laser eye surgery—small incision lenticule extraction (SMILE) [2:11:45]

How SMILE works

SMILE (small incision lenticule extraction) is an interesting procedure
It’s using a single laser, a femtosecond laser
Consider again the book analogy, the book is opened to page 100 Imagine creating a little tunnel down to page 100 and then remove pages 100-110 while keeping the incision really tiny This is performed through a very small keyhole procedure
This seems to be an effective procedure
Imagine creating a little tunnel down to page 100 and then remove pages 100-110 while keeping the incision really tiny This is performed through a very small keyhole procedure
This is performed through a very small keyhole procedure

Peter asks, “ What problem is it solving? Given how effective LASIK is. ”

This was designed to solve dry eye
The problem it really solved, especially outside the United States, was needing only 1 laser instead of 2 PRK can also be done with just 1 laser but it has a prolonged recovery time The idea with SMILE is to provide a LASIK-like return of vision with a single laser
SMILE technology is evolving
Steven hasn’t seen any data that shows that SMILE is in any way better than LASIK or even equal to LASIK; but it seems to be a very good procedure
He doesn’t currently use the SMILE procedure; but when the next generations of it rise to the point when they are better than what he is doing he will probably adopt it
PRK can also be done with just 1 laser but it has a prolonged recovery time
The idea with SMILE is to provide a LASIK-like return of vision with a single laser

Glaucoma: definition, causes, symptoms, and care [2:13:45]

When the optometrist blows air at the eye, is that to detect glaucoma ? That’s a way of measuring the intraocular pressure that he doesn’t use It has the advantage of not requiring the patient to be touched with anything This can indent the cornea with a known amount of force from an air puff and look at how it optically deforms The disadvantage to the air puff, and it’s not really considered the gold standard of measuring pressure, is that if the patient blinks really quickly and squeezes, there can be a false reading with that type of air puff tonometry He doesn’t typically use
Steven uses 2 ways to measure intraocular pressure, both of which physically indent the cornea After he anesthetizes the eye with a known amount of force, then he can look at the amount of force required to cause a certain amount of indentation
Glaucoma is probably about a hundred different diseases, but they all share the final common pathway of damage to the optic nerve (the nerve in the back of the eyes) and the cranial nerve (mentioned at the beginning), that is somehow related to pressure So this is a pressure related optic neuropathy Now what’s odd about glaucoma is that there are people who have totally normal pressures with relation to the population, but that pressure’s too high for them and they can develop damage to their optic nerve
That’s a way of measuring the intraocular pressure that he doesn’t use
It has the advantage of not requiring the patient to be touched with anything
This can indent the cornea with a known amount of force from an air puff and look at how it optically deforms
The disadvantage to the air puff, and it’s not really considered the gold standard of measuring pressure, is that if the patient blinks really quickly and squeezes, there can be a false reading with that type of air puff tonometry
He doesn’t typically use
After he anesthetizes the eye with a known amount of force, then he can look at the amount of force required to cause a certain amount of indentation
So this is a pressure related optic neuropathy
Now what’s odd about glaucoma is that there are people who have totally normal pressures with relation to the population, but that pressure’s too high for them and they can develop damage to their optic nerve

Symptoms of glaucoma

Peter asks about the symptoms of glaucoma
It’s funny, this question just sort of triggered a memory Steven had a patient when he was in training years ago and he was explaining to a patient about glaucoma The patient had no symptoms at all One wouldn’t notice glaucoma at all and yet, if it’s not diagnosed, it could be really bad And the patient said, “ Well, if it has no symptoms, what do I care? What’s the point? ” Steven realized what he should have said was it has no symptoms until the very end
The peripheral vision is damaged at the end of glaucoma
Most people will not detect a slight reduction in their peripheral vision, particularly if it’s segmental There will be just a little area off to the side that they can’t see This is particularly true if the other eye is covering for that area
But as glaucoma progresses, it can affect central vision, and then it becomes symptomatic
Luckily glaucoma has become much more treatable The pharmacological management of glaucoma has gotten way better And there are numerous laser procedures that can treat glaucoma, what are referred to as minimally invasive glaucoma surgery (MIGS)
Steven had a patient when he was in training years ago and he was explaining to a patient about glaucoma
The patient had no symptoms at all
One wouldn’t notice glaucoma at all and yet, if it’s not diagnosed, it could be really bad
And the patient said, “ Well, if it has no symptoms, what do I care? What’s the point? ”
Steven realized what he should have said was it has no symptoms until the very end
There will be just a little area off to the side that they can’t see
This is particularly true if the other eye is covering for that area
The pharmacological management of glaucoma has gotten way better
And there are numerous laser procedures that can treat glaucoma, what are referred to as minimally invasive glaucoma surgery (MIGS)

Cause of glaucoma

Peter asks “ what’s the 80/20 of this? 80% of them are caused by what ”
So 80% of them are caused by what is referred to as garden variety chronic open angle glaucoma This means that the glaucoma is not a function of the anatomy of the front of the eye being too crowded, where the fluid can’t get out It’s more a problem of overproduction of fluid inside the eye, and the pressure is too high inside the eye This is the aqueous fluid not vitreous fluid It is not know what causes this; the pathogenesis is likely multifactorial It runs in families, so there is a family history component but it’s not simple heredity It is not coupled with diabetes There’s some relationship to hypertension, blood pressure; but it can be seen in patients who are not hypertensive at all It’s very common
This means that the glaucoma is not a function of the anatomy of the front of the eye being too crowded, where the fluid can’t get out
It’s more a problem of overproduction of fluid inside the eye, and the pressure is too high inside the eye This is the aqueous fluid not vitreous fluid
It is not know what causes this; the pathogenesis is likely multifactorial
It runs in families, so there is a family history component but it’s not simple heredity
It is not coupled with diabetes
There’s some relationship to hypertension, blood pressure; but it can be seen in patients who are not hypertensive at all
It’s very common
This is the aqueous fluid not vitreous fluid

“ Every eye surgeon sees glaucoma patients daily, multiple glaucoma patients daily ” – Steven Dell

Peter notes, “ So presumably like any neuropathy , if you catch it early enough, it’s fully reversible, and if you catch it too late, there you damage it, or is it… Because this is a central nerve, not a peripheral nerve ”
Yes, Steven thinks the progression can be arrested; but once damage has occurred, it can’t be undone Such as optic nerve damage
Peter asks, “ So it’s not like sciatica ”
No, Steven doesn’t think so Once there’s been damage, he expects that damage to remain So it’s not unusual for a patient to have what is referred to as a visual field defect This is a little area missing from their field of vision Then his goal becomes to prevent that defect from getting any bigger; this is possible once it is identified
Peter asks at what age this starts to become a concern, when should screening begin?
Steven things everyone should be screened for glaucoma when they go to the eye doctor for a yearly exam The appearance of the optic nerve is examined as well as the pressure, and those are probably the two most important things to look for with glaucoma
Incidence does go up with age; so in the 50’s and beyond, it’s much more important to pay attention to glaucoma
Peter notes, “ presumably in the developing world where people aren’t going to get eyecare or even in the United States, if people don’t choose to get eyecare or can’t afford to get eyecare, it’s a bigger risk because they’ll only present when they have symptoms ”
That’s exactly right
Such as optic nerve damage
Once there’s been damage, he expects that damage to remain
So it’s not unusual for a patient to have what is referred to as a visual field defect This is a little area missing from their field of vision Then his goal becomes to prevent that defect from getting any bigger; this is possible once it is identified
This is a little area missing from their field of vision
Then his goal becomes to prevent that defect from getting any bigger; this is possible once it is identified
The appearance of the optic nerve is examined as well as the pressure, and those are probably the two most important things to look for with glaucoma

Tips for preserving eye health [2:20:00]

Peter summarizes, “ we think about the longevity of the longevity of the eye as a pretty important thing. If you want to figure out a way to live to a hundred… ” Think about how to delay the onset of atherosclerosis And an aggressive strategy to mitigate cancer, Alzheimer’s disease, etc. But these other things don’t get enough attention: teeth, ears, and eyes
Think about how to delay the onset of atherosclerosis
And an aggressive strategy to mitigate cancer, Alzheimer’s disease, etc.
But these other things don’t get enough attention: teeth, ears, and eyes

“ I mean, you don’t want to get to be a hundred and have no teeth. And you don’t want to get to be a hundred and be deaf. And you don’t want to get to be a hundred and be blind .” – Peter Attia

Steven notes, “ Trying to get a kid to wear sunglasses is tough ”
Hats are important as well, that’s a very good and effective way to protect the eyes But it’s not enough because a certain amount of light bounces off and hits the bottom of one’s cheek and goes right into the eye
But it’s not enough because a certain amount of light bounces off and hits the bottom of one’s cheek and goes right into the eye

Supplements

Nutritional supplements might have some effect
Vitamin C deficiency is associated with an elevated risk of cataract But it’s been shown conclusively that vitamin C supplementation to super normal levels does not protect against cataract formation
Other antioxidants that have been looked at (vitamins A, C, and E) basically have no effect on cataract formation There is a little bit of mixed weak evidence for lutein and zeaxanthin as possibly being protective for cataract and macular degeneration
In the drugstore they sell AREDS formula for macular degeneration ; that stands for Age-Related Eye Disease Study
The Age-Related Eye Disease Study was a National Eye Institute initiative First they looked at C, E and beta-carotene with zinc and a little copper They put the copper in because they were worried about copper deficiency with zinc supplementation Then they got concerned about beta-carotene, so they did another study where they took beta-carotene out and put in lutin and zeaxanthine, powerful antioxidants They showed this supplementation could delay or reduce the conversion of mild macular degeneration to severe disease; but it had not effect on severe disease Interestingly, it had no effect on people who didn’t have macular degeneration; it didn’t prevent them from going on to get it Most ophthalmologists believe there’s something there, there’s some signal embedded in that noise
Light is also a big risk for macular degeneration It’s a dose thing One wants enough light to avoid becoming nearsighted but not so much that the retinas are fried and cataracts develop
He Thinks some form of broad spectrum antioxidant protection makes sense
But it’s been shown conclusively that vitamin C supplementation to super normal levels does not protect against cataract formation
There is a little bit of mixed weak evidence for lutein and zeaxanthin as possibly being protective for cataract and macular degeneration
First they looked at C, E and beta-carotene with zinc and a little copper
They put the copper in because they were worried about copper deficiency with zinc supplementation
Then they got concerned about beta-carotene, so they did another study where they took beta-carotene out and put in lutin and zeaxanthine, powerful antioxidants
They showed this supplementation could delay or reduce the conversion of mild macular degeneration to severe disease; but it had not effect on severe disease
Interestingly, it had no effect on people who didn’t have macular degeneration; it didn’t prevent them from going on to get it
Most ophthalmologists believe there’s something there, there’s some signal embedded in that noise
It’s a dose thing
One wants enough light to avoid becoming nearsighted but not so much that the retinas are fried and cataracts develop

Screen time and eye health [2:24:15]

Peter asks about screen use, “ So what do we know about phones specifically and computers? ”

People ask Steven all the time about blue-blocking glasses
The amount of UV radiation coming off of screens is sufficiently low that there has been no evidence at all that it’s going to cause macular degeneration in the same way that one can’t get a sunburn from a screen
The amount of blue light that one gets from going outside is many, many, many orders of magnitude greater than what one can get from screens
Blue light can mess up one’s circadian rhythm If you take someone and expose them to blue light at noon, that’s great But then expose them to that at 11:00 PM when they are going to try to go to sleep, that’s messed up
It’s almost like running a gigantic experiment with humans Think about a turtle, consider a species of turtle that spends 90% of its time in the water, 10% on land Now take that and flip it so it spends 10% of its time in the water Now there seems to be something weird going on with these turtles; yes, they’re surviving, but they’re in a very altered environment compared to what they were evolved to deal with
If you take someone and expose them to blue light at noon, that’s great
But then expose them to that at 11:00 PM when they are going to try to go to sleep, that’s messed up
Think about a turtle, consider a species of turtle that spends 90% of its time in the water, 10% on land
Now take that and flip it so it spends 10% of its time in the water
Now there seems to be something weird going on with these turtles; yes, they’re surviving, but they’re in a very altered environment compared to what they were evolved to deal with

“ So giving people blue light from a screen that’s bright at 10:00 PM, 11:00 PM, and then asking them to go to sleep is a problem ” – Steven Dell

Exposure to blue light from a screen at night is not damaging their retinas or giving them cataracts, but may be messing up their circadian rhythms Although it is hard to disentangle that from the total amount of light that they’re seeing, which is also unnatural and what comes with it Peter notes, “ There seems to be a difference between watching TV and checking email before bed. Maybe neither are ideal, but one seems demonstrably worse, at least for me ”
Steven has software embedded in all of his PCs that changes the color temperatures f.lux is a software that’s free; it will take the blue light sequentially out of the monitor as the day goes on, as the evening goes on to the point that it’s like super amber, as it gets close to bedtime He really thinks that’s great
Although it is hard to disentangle that from the total amount of light that they’re seeing, which is also unnatural and what comes with it
Peter notes, “ There seems to be a difference between watching TV and checking email before bed. Maybe neither are ideal, but one seems demonstrably worse, at least for me ”
f.lux is a software that’s free; it will take the blue light sequentially out of the monitor as the day goes on, as the evening goes on to the point that it’s like super amber, as it gets close to bedtime He really thinks that’s great
He really thinks that’s great

Contact lenses: good hygiene and considerations [2:27:45]

Peter asks what else people should think about to protect their eyes

He notes, the big takeaways for him have been the importance of sunglasses, artificial tears, taking one’s contact lenses out as frequently as possible, right? Don’t sleep in contact lenses and stuff like that The daily ones seem best if one can afford it It makes more sense than the 2-week ones that have to be washed every night Steven thinks the most important thing is to just get them out of the eye He doesn’t like extended-wear contact lenses
As an eye surgeon, he tends to see a selected sample of patients who are the problems The people who have sight-threatening infections from sleeping typically in contact lenses Yes, he realizes there are millions of people who sleep in their contacts and don’t get infections, but the people who end up in his office have had problems; and some of them quite devastating problems He’s not a big fan of sleeping in contact lenses in general, but if one is going to sleep in them, he’d rather they be a perfect, pristine, new pair every single time And get them out as quickly as you possibly can
Don’t sleep in contact lenses and stuff like that
The daily ones seem best if one can afford it
It makes more sense than the 2-week ones that have to be washed every night
Steven thinks the most important thing is to just get them out of the eye
He doesn’t like extended-wear contact lenses
The people who have sight-threatening infections from sleeping typically in contact lenses
Yes, he realizes there are millions of people who sleep in their contacts and don’t get infections, but the people who end up in his office have had problems; and some of them quite devastating problems
He’s not a big fan of sleeping in contact lenses in general, but if one is going to sleep in them, he’d rather they be a perfect, pristine, new pair every single time And get them out as quickly as you possibly can
And get them out as quickly as you possibly can

A bonus benefit from repairing cataracts [2:29:00]

Peter notes, “ The other takeaway for me, is not to be so afraid of cataracts. They’re inevitable. And… there’s a potential silver lining, which is not only the improvement of your vision, but potentially the correction of other age-related visual changes. ”
Steven agrees, it’s interesting that once word got out in the community that this was something that could be done, he saw people coming in asking for cataract surgery a little sooner than they otherwise would Because they know that this added benefit is a potential possibility In the old days when intraocular lenses were not available, people would have to wear these cataract glasses These super thick lenses that were very, very powerful and magnified everything It didn’t really work all that well optically Without implant lenses, their prescription was typically about +10 People with a prescription of -10 can’t see without glasses So this was the context in which people would put off cataract surgery as long as possible
Peter asks if cataract surgery is one and done; do people every need reoperations It’s not unheard of; if the implant lens isn’t functioning, it can be replaced
Because they know that this added benefit is a potential possibility
In the old days when intraocular lenses were not available, people would have to wear these cataract glasses These super thick lenses that were very, very powerful and magnified everything It didn’t really work all that well optically Without implant lenses, their prescription was typically about +10 People with a prescription of -10 can’t see without glasses
So this was the context in which people would put off cataract surgery as long as possible
These super thick lenses that were very, very powerful and magnified everything
It didn’t really work all that well optically
Without implant lenses, their prescription was typically about +10
People with a prescription of -10 can’t see without glasses
It’s not unheard of; if the implant lens isn’t functioning, it can be replaced

Questions about corrective eye surgery [2:31:30]

The other question Peter had on laser surgery is, how stable does one’s prescription need to be? There are 3 variables to think about 1) The cornea 2) The length of the eye 3) The lens itself The lens will continue to change throughout life, but typically not until one’s in their 50’s, 50’s, and 70’s, when cataract formation will start to affect the light bending power of the lens The cornea should not be changing So just the length of the eye needs to be fixed And typically, unless someone is going back to law school or reading 30 hours a day, that is typically finished changing in the early twenties (around 23, 24) Prescriptions really shouldn’t be worsening unless one is developing some cataract formation
He often tells patients that at some point they will start to develop some cataract formation
There are 3 variables to think about
1) The cornea
2) The length of the eye
3) The lens itself
The lens will continue to change throughout life, but typically not until one’s in their 50’s, 50’s, and 70’s, when cataract formation will start to affect the light bending power of the lens
The cornea should not be changing
So just the length of the eye needs to be fixed And typically, unless someone is going back to law school or reading 30 hours a day, that is typically finished changing in the early twenties (around 23, 24) Prescriptions really shouldn’t be worsening unless one is developing some cataract formation
And typically, unless someone is going back to law school or reading 30 hours a day, that is typically finished changing in the early twenties (around 23, 24)
Prescriptions really shouldn’t be worsening unless one is developing some cataract formation

Risk from exposure to ionizing radiation

He does see people who do fluoroscopy , health professionals who are exposed to ionizing radiation ; this increases the risk of cataract formation A ship captain on a boat that’s carrying nuclear waste who smokes and is also a diabetic is going to develop cataracts a lot sooner
A ship captain on a boat that’s carrying nuclear waste who smokes and is also a diabetic is going to develop cataracts a lot sooner

How an eye exam can be a window into metabolic illness [2:33:45]

Peter asks about hemoglobin A1C , which is a pretty crude, unimpressive way to assess glycosylation He doesn’t think this measure is helpful outside of extremes But he thinks the eye is the most sensitive end organ to excessive glycosylated hemoglobin And it’s also one of the few things one can look at directly Could an angio of the eyes be done noninvasively? Yes Peter thought that was really cool, he liked knowing that he had beautiful little vasculature back there
Peter asks if there will come a day when everybody has an angio done on their eyes every year, to look for changes? He notes, “ Your hemoglobin A1C might only be 5.5, your quote unquote normal, but that might actually reflect higher turnover of RBCs and in reality, there’s a problem. ”
He doesn’t think this measure is helpful outside of extremes
But he thinks the eye is the most sensitive end organ to excessive glycosylated hemoglobin
And it’s also one of the few things one can look at directly
Could an angio of the eyes be done noninvasively? Yes Peter thought that was really cool, he liked knowing that he had beautiful little vasculature back there
Peter thought that was really cool, he liked knowing that he had beautiful little vasculature back there
He notes, “ Your hemoglobin A1C might only be 5.5, your quote unquote normal, but that might actually reflect higher turnover of RBCs and in reality, there’s a problem. ”

“ One of the really interesting things about the eyeballs, is that it’s a transparent organ… you can just look in and see what the problem is” – Steven Dell

For example, there is a layer of brain tissue readily available for observation, including its capillary network So he can look and see, are these capillaries damaged? This is something seen in diabetics Are they exudating fluid? Are they leaking fluid? This is a very early sign of diabetic retinopathy The lens could be imaged to determine if glucose is leaching into this lens? Does it contain more glucose than one would expect a normal individual to have in their lens? Might that be a screening technique for diabetic disease… probably yes And what about the fact that diabetes manifests primarily as a microvascular disease in so many end organs and in the eye, one can actually directly visualize this microvascular disease occurring If it’s in the eye, it’s probably in the kidney, it’s probably in the toes
Peter notes this diagnosis is not binary; this is a spectrum When the hemoglobin A1C is 6.5%, the person has type II diabetes But at 6% they’re prediabetic And at 5.6%, we say they’re normal
So he can look and see, are these capillaries damaged? This is something seen in diabetics Are they exudating fluid? Are they leaking fluid? This is a very early sign of diabetic retinopathy
The lens could be imaged to determine if glucose is leaching into this lens? Does it contain more glucose than one would expect a normal individual to have in their lens? Might that be a screening technique for diabetic disease… probably yes
And what about the fact that diabetes manifests primarily as a microvascular disease in so many end organs and in the eye, one can actually directly visualize this microvascular disease occurring If it’s in the eye, it’s probably in the kidney, it’s probably in the toes
This is something seen in diabetics
Are they exudating fluid? Are they leaking fluid?
This is a very early sign of diabetic retinopathy
Does it contain more glucose than one would expect a normal individual to have in their lens?
Might that be a screening technique for diabetic disease… probably yes
If it’s in the eye, it’s probably in the kidney, it’s probably in the toes
When the hemoglobin A1C is 6.5%, the person has type II diabetes But at 6% they’re prediabetic And at 5.6%, we say they’re normal
But at 6% they’re prediabetic
And at 5.6%, we say they’re normal

“ A much more interesting way to go about gaining a foothold in our understanding of a person’s metabolic health is to create this as now a new standard, right? ” – Peter Attia

Peter wants to make sure that these nearly invisible arteries and capillaries are perfect And when they cease to be, it’s going to prompt investigation Whether it be lipids, whether it be glucose, whether it be blood pressure All of the things that can damage a microvascular system, this becomes a beautiful window in which we can look at them
What is the cost of doing that test?
Steven notes, it’s very inexpensive and “ I honestly believe that we would see perturbations in the glucose migration into the lens way sooner than we would see architectural changes in the retinal microvasculature ”
The technology to measure glucose in the lens doesn’t exist commercially, although it’s being studied
He could look at how the lens essentially reacts to light that is shined into the lens with a particular wavelength, and determine how much glucose there is in that lens, and is that abnormal compared to a normal population?
But looking at the retinal vasculature, he can do that with optical coherence tomography And he can image, in a noninvasive way, the capillary network
In initial diagnosis and screening, the canary in the coal mine is actually going to be the lens distortion due to the osmotic effect of glucose
But what happens very commonly is that a diabetic will come into us and say, “ My sugar is well controlled. My doctor told me I’m under great control. ”
But when he looks at their retina, there’s no way they’re under great control They have fluid exuding into their retina There are what are referred to as hard exudates There are microaneurysms in their capillary vasculature; these are signs that their diabetes is out of control Then he’ll say, “ I’m glad that your A1C was normal; would you mind going back to your doctor and mentioning that I saw direct evidence of problems with your microvasculature? ” This problem observed in the eye probably exists everywhere in the body Typically the endocrinologist will accept this news They’ll say, “ Okay, well for this individual, that level of A1C is not acceptable. ” Typically, they’ve been very receptive because they know we can directly visualize this
Peter feels strongly that ophthalmology should be more integrated into medicine than less What ophthalmologists do in some ways operates outside of what the surgeons, and the internists, and endocrinologists do Obviously here’s an example of where an ophthalmologist can see something important to systemic health He thinks there should be more of an integration of this People might not have appreciated that ophthalmologists get to directly look at the brain They can look directly at the central nervous system in a way that a gastroenterologist can directly look at the colon That’s why colon cancer screening is so freaking effective; the doctor gets to look with the naked eye directly at a polyp as it becomes cancerous And he’s so thankful for them, because of all they can save us from
And when they cease to be, it’s going to prompt investigation Whether it be lipids, whether it be glucose, whether it be blood pressure
All of the things that can damage a microvascular system, this becomes a beautiful window in which we can look at them
Whether it be lipids, whether it be glucose, whether it be blood pressure
And he can image, in a noninvasive way, the capillary network
They have fluid exuding into their retina
There are what are referred to as hard exudates
There are microaneurysms in their capillary vasculature; these are signs that their diabetes is out of control
Then he’ll say, “ I’m glad that your A1C was normal; would you mind going back to your doctor and mentioning that I saw direct evidence of problems with your microvasculature? ” This problem observed in the eye probably exists everywhere in the body Typically the endocrinologist will accept this news They’ll say, “ Okay, well for this individual, that level of A1C is not acceptable. ” Typically, they’ve been very receptive because they know we can directly visualize this
This problem observed in the eye probably exists everywhere in the body
Typically the endocrinologist will accept this news
They’ll say, “ Okay, well for this individual, that level of A1C is not acceptable. ”
Typically, they’ve been very receptive because they know we can directly visualize this
What ophthalmologists do in some ways operates outside of what the surgeons, and the internists, and endocrinologists do
Obviously here’s an example of where an ophthalmologist can see something important to systemic health
He thinks there should be more of an integration of this
People might not have appreciated that ophthalmologists get to directly look at the brain
They can look directly at the central nervous system in a way that a gastroenterologist can directly look at the colon That’s why colon cancer screening is so freaking effective; the doctor gets to look with the naked eye directly at a polyp as it becomes cancerous And he’s so thankful for them, because of all they can save us from
That’s why colon cancer screening is so freaking effective; the doctor gets to look with the naked eye directly at a polyp as it becomes cancerous
And he’s so thankful for them, because of all they can save us from

“ It is amazing that we have the ability to directly observe the brain and the vascular tree, and so that’s very, very helpful ” – Steven Dell

Selected Links / Related Material

Medication in development to restore elasticity to the lens of the eye : Topical lipoic acid choline ester eye drop for improvement of near visual acuity in subjects with presbyopia: a safety and preliminary efficacy trial | Eye (M S Korenfeld et al . 2021) | [25:00]

Review of interventions to treat myopia and discussion of eye drops : Myopia: attempts to arrest progression | The British Journal of Ophthalmology (S M Saw et al. 2002) | [30:30]

Book about Harold Ridley, the inventor of ocular implants : Sir Harold Ridley and His Fight for Sight: He Changed the World So That We May Better See It by David J. Apple (2006) | [1:14:00]

Effects of Omega-3 supplementation on dry eye : Effects of Omega-3 Supplementation on Exploratory Outcomes in the DREAM Study | Opthalmology (M Oydanich et al . 2020) | [1:33:45]

The DREAM study on dry eye : The DREAM Study | Emma Wells, PENN Medicine (2017) | [1:34:15]

Pathophysiology of dry eye : Intense pulsed light for evaporative dry eye disease | Clinical Ophthalmology (S J Dell 2017)

People Mentioned

Harold Ridley (British ophthalmologist who invented intraocular lenses) [1:12:45]
Marguerite McDonald (The first person to perform PRK) [1:46:15]

Steven Dell is a board certified ophthalmologist in Austin and the Medical Director of Dell Laser Consultants . He is an internationally recognized leader in refractive eye surgery specializing in: LASIK laser eye surgery, cataract surgery and refractive lens exchange. He is the chief Medical Editor of the medical journal Cataract and Refractive Surgery Today . He is the Chair-emeritus and President-emeritus of The American-European Congress of Ophthalmic Surgery . He is a principal investigator for a variety of FDA clinical trials in the field of eye surgery. He has invented several surgical instruments and devices, and holds over 20 US and international patents in eye surgery including the: Dell Astigmatism Marker™, Dell Fixation Ring™, Dell PlumeSafe Ophthalmic Evacuation System™, and Dell PlumeSafe Handpiece™. He is also the author of numerous textbook chapters and peer-reviewed journal articles. [ Dell Laser Consultants ]

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