Peter Attia MD198 - Eye health—everything you need to know | Steven Dell, M.D.
EVERY SPOKEN WORD
150 min read · 30,194 words- 0:00 – 0:10
intro
- PAPeter Attia
[upbeat music] Hey, everyone. Welcome to the Drive podcast. I'm your host, Peter Attia. [upbeat music]
- 0:10 – 11:33
Why Steven chose ophthalmology, and the crossovers to other medical disciplines
- PAPeter Attia
Hey, Steven. Thank you so much for, for coming over. As we were talking about, I don't really do many of these in person anymore, uh, often just out of sheer laziness, but I, I do enjoy it a lot more, so it, the, the fact that, I know it was a bit of a hassle, you had to probably change clinic or something today, but anyway, really appreciate you coming out. And, uh, this is a topic that, you know, I think everybody has questions on this topic.
- SDSteven Dell
Right.
- PAPeter Attia
And everybody, myself included, is comically ignorant on this topic. I, I mentioned to you a few minutes ago the extent of my knowledge from medical school. I remember there's an optic nerve. I remember it's a cranial nerve. I think it's even the second cranial nerve.
- SDSteven Dell
There you go. You're ahead of the game.
- PAPeter Attia
I remember something called a fovea.
- SDSteven Dell
Right.
- PAPeter Attia
And I know there's a blind spot, but I've kind of forgotten why. So it's safe to say my knowledge of this topic right now is probably at par with everybody's, right?
- SDSteven Dell
Well, that's, you know, 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.
- PAPeter Attia
Has there ever been a discussion about suggesting that ophthalmologists, um, don't need to do the four-year MD degree? Like how much of what you learned in medical school became relevant in your residency?
- SDSteven Dell
Uh, actually quite a lot, honestly.
- PAPeter Attia
Yeah?
- SDSteven Dell
Yeah, because you think about it, the eyeball, there's really 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. Um, there are a lot of crossovers to other medical disciplines. All of the, uh, cellular processes are the same. We operate adjacent to the eye. I think it's important for us 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, of visual training, basically optometry-
- PAPeter Attia
Yes
- SDSteven Dell
... which deals with the eye, but not all of the, the surgical stuff. So we work in a collaborative fashion with optometrists. Uh, and 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, like glaucoma, for example. Um, and we work in a collaborative fashion with them.
- PAPeter Attia
And, um, does everyone in an ophthalmology residency spend time operating? Th- there's no, there's no non-surgical discipline to this, right? It doesn't bifurcate in the training?
- SDSteven Dell
Well, it does, actually. There are non-surgical ophthalmologists, but I think they all start out as surgeons. To become an ophthalmologist, you're really training to become an eye surgeon.
- PAPeter Attia
Mm-hmm.
- SDSteven Dell
But there are, for example, neuro-ophthalmologists, which are really more neurologists than eye surgeons. In fact, they, it's typical that they don't do eye surgery. Uh, so there, there are some ophthalmologists who don't do eye surgery.
- PAPeter Attia
You know, one of my sort of lasting memories from residency was stealing suture from the ophthalmology OR at Hopkins because, um [lip smack] I guess for people who don't know, uh, the number of the suture, of course, gets larger, the suture gets smaller.
- SDSteven Dell
Right.
- PAPeter Attia
So a, a, an O suture is, like you can see how thick it is. It's like a piece of rope.
- SDSteven Dell
Right.
- PAPeter Attia
1-0, 2-0, 3-0. By the time you're at 4-0, it's-
- SDSteven Dell
Yeah
- PAPeter Attia
... it's actually quite thin.
- SDSteven Dell
Right. We use 11-0.
- PAPeter Attia
Exactly.
- SDSteven Dell
Yeah, so.
- PAPeter Attia
In cardiac surgery, you're using a 7-0.
- SDSteven Dell
Yeah.
- 11:33 – 25:21
Anatomy of the eye, common types of vision loss, and age-related vision changes
- PAPeter Attia
So this is probably a good moment to, to sort of take a step back and get into some of the anatomy and, and get me up to speed, and everybody else by extension, on what it is we are talking about here. Because even the word retina-
- SDSteven Dell
Yeah
- PAPeter Attia
... cornea, these are like, I kind of know the retina's at the back of the eye.
- SDSteven Dell
[laughs]
- PAPeter Attia
That, like, it's just embarrassing-
- SDSteven Dell
Right
- PAPeter Attia
... Steven, how much of a Luddite I am when it comes to this part of the body. So, um, I, I can say this: literally talk to me like I'm a four-year-old. [laughs]
- SDSteven Dell
Okay. All right.
- PAPeter Attia
And explain the eye to me.
- SDSteven Dell
That's good. That'll work for both of us. So, you know, uh, it's funny, it's funny you mention that because I don't typically see kids in my practice, but there is one disease state where I do see kids, and that's because we did some research in that area that- Anyway, allows me to see kids. And when you explain the eye to a kid and you say, "Well, the eye is like a camera, and the film in the back, that's the retina," and they look over at their parents like, "What is this guy-"
- PAPeter Attia
What's a camera?
- SDSteven Dell
"What is this guy talking about?" [laughs]
- PAPeter Attia
Isn't a camera the thing on your phone? [laughs]
- SDSteven Dell
[laughs] What is he talking about? Film?
- PAPeter Attia
[laughs]
- SDSteven Dell
What, what is that? You know, a s- a 50-year-old understands that.
- PAPeter Attia
Yeah.
- SDSteven Dell
But literally the eye is kind of built like a camera, where in the very front you have the cornea, which is kind of like the covering on the front of a watch. That's the thing that a contact lens would sit on.
- PAPeter Attia
Sure.
- SDSteven Dell
And then the next thing you encounter is the pupil, which is the hole in the iris. Behind that is the lens. We refer to it as the lens, but it's really one of a couple of different lenses inside the eye, but the lens behind the pupil. Then you have the vitreous cavity, and then in the very back, the retina, which attaches to the optic nerve, and that's what goes to the brain. So images come in, they're bent by the cornea first, then bent again by the lens, and then they focus hopefully on the retina. So 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 our discussion, about 20 feet or beyond, where li- r- li- light rays come in parallel, and they're bent so that they fall perfectly on the retina. And-
- PAPeter Attia
And what does that mean, fall perfectly on the retina?
- SDSteven Dell
They come, yeah.
- PAPeter Attia
Meaning they, uh, uh, is the r- like h- if, if you think about the, um, back of the eye here-
- SDSteven Dell
Right
- PAPeter Attia
... what fraction of the back of this sphere is considered retina?
- SDSteven Dell
All of it.
- PAPeter Attia
Everything.
- SDSteven Dell
Yeah, all of it. The whole back of the eye is coated essentially by retina. But there is the fovea you mentioned earlier. That's the point where you cast your gaze. So the image that, of the thing you're looking at falls on the fovea, which is the very center, the bullseye, literally, of the, of the retina. So when I'm looking at you, images from you are falling on the fovea of both of my retinas. Now, if someone is nearsighted, those images come into focus in a point that is not exactly on the retina. And so that, that can become a, a problem.
- PAPeter Attia
And nearsighted, again, the way I used to remember this-
- SDSteven Dell
Yeah
- 25:21 – 31:25
Eye drops that can potentially improve vision
- SDSteven Dell
make it bigger. And interestingly, one of the big pharmacological, I think, frontiers that we're on the cusp of seeing are drugs that intentionally shrink the aperture, uh, in the pursuit of increased depth of focus. So students of photography will know that the smaller the aperture, the smaller the hole, the more stuff is in focus at the same time. So if you can make the pupil small pharmacologically and get it into the sweet spot, which is probably about 1.6 millimeters, you can suddenly see up close again because you've inc- you've expanded the depth of focus.
- PAPeter Attia
Wait, this is... Let me make sure I understand this.
- SDSteven Dell
Yeah. [laughs]
- PAPeter Attia
You're saying that putting the lens aside for a moment-
- SDSteven Dell
Right. Right
- PAPeter Attia
... which is a great source of the pathology, the inability of the lens to move in and out on the, call it the Z axis, if we want-
- SDSteven Dell
Right
- PAPeter Attia
... to think of it that way, you now have another way to manipulate your ability to see things close up if you could force the aperture to be in a position that isn't necessarily dictated by the availability of light?
- SDSteven Dell
That's exactly right. So imagine, it's kind of like squinting.
- PAPeter Attia
Yeah.
- SDSteven Dell
You know, if you can, you squint, you're reducing the aperture through which you're looking, and you're filtering out... Optically what's happening is you're filtering out all of the light rays that are not perfectly parallel. And if you 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, you can actually resolve it. You can actually see it. And that's why pharmacologically, if you shrink the pupil, you could once again see up close.
- PAPeter Attia
Now, this again is a little counterintuitive to me because anybody who's in my shoes who's experiencing, uh, farsightedness-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... or, or I actually shouldn't say that. Presby-
- SDSteven Dell
Presbyopia.
- PAPeter Attia
Presbyopia.
- SDSteven Dell
Yeah.
- PAPeter Attia
Um, knows that nothing makes it worse than darkness.
- SDSteven Dell
Correct.
- PAPeter Attia
And so you're in that rest- Th- th- this, there's two scenarios where it, it wreaks havoc. The first is one of my children has a train book that why these guys wrote a book in, like, six-point font that they know parents are gonna read their kids in bed when it's kind of dark, it's, it's beyond me.
- SDSteven Dell
Right.
- PAPeter Attia
Like, there should be a mandatory 24-point font for-
- SDSteven Dell
Mm
- PAPeter Attia
... nighttime books for little kids. But anyway, he's got this one book, and he even tells me before he wants that book read. He's like, "Daddy, go get your glasses."
- SDSteven Dell
Right.
- PAPeter Attia
Um, and then the other place is the restaurant-
- SDSteven Dell
Right
- PAPeter Attia
... where it's usually dimly lit. But in both of those situations, isn't my aperture narrowed because-
- SDSteven Dell
No.
- PAPeter Attia
Oh, no, no, of course not. It's the opposite.
- 31:25 – 33:04
The explanation for different eye colors
- PAPeter Attia
Um, is there any clear evolutionary explanation for why different eye colors have emerged? Why, why is-- What, you know, what's the advantage of brown iris versus blue?
- SDSteven Dell
Yeah. It's, uh, protection from UV light and from, from visible light in the same way that different skin tones have emerged.
- PAPeter Attia
I see.
- SDSteven Dell
So typically you see dark-eyed-
- PAPeter Attia
People closer to the equator
- SDSteven Dell
... people closer, clustered closer to the equator because, you know, the l- visible light and UV light and infrared light or infrared radiation are really destructive. And as you might remember, this is one of the few things that people remember from medical school about the retina, but it's one of the most metabolically active tissues in the body, if not the most metabolically active tissue. And because it's constantly being bombarded with radiation effectively, it's prone to free radical formation.
- PAPeter Attia
Mm.
- SDSteven Dell
So the, what's called the retinal pigment epithelium, which is the pigmented layer behind the retina, underneath the retina, that is responsible from sh- for shielding the vascular supply behind the retina from all of this radiation because that, that vascular network behind the retina has a very high oxygen tension, and it would be prone to pr- free radical formation if it were constantly being bombarded by UV light, infrared radiation, visible light. And that's why you see in people near the equator more pigment. And that's also true of the iris as well.
- 33:04 – 39:37
Physiology of the eye and its connections to the brain
- PAPeter Attia
So the other thing I do remember vaguely from medical school is rods and cones.
- SDSteven Dell
Yeah. [laughs]
- PAPeter Attia
And, uh, of course, I also remember a few other things now that we're talking about it, about, you know, where the, um, wh- which part of the brain actually does the signal processing and stuff.
- SDSteven Dell
Yeah.
- PAPeter Attia
So, uh, let's go back to the light hitting, and what are the rods and cones and how are they processing that signal?
- SDSteven Dell
Right. So, you know, you might remember cones are primarily for your daytime vision, and they're clustered in the center of your visual sphere. So in the center of the-- near the center of the what we refer to as the macula, which is the central portion of the retina, and the very center of the macula is the fovea.
- PAPeter Attia
Fovea, right.
- SDSteven Dell
Right. So that's primarily 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, you know, 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, "Oh, that's a, some kind of a tiger over there. Something's moving in my periphery. I need to be aware of that." So, um, that's primarily the difference in responsibility.
- PAPeter Attia
And is each rod and each cone-- W- is it, is it, is each one a single cell?
- SDSteven Dell
Yes, that's right. They're each highly specialized cells.
- PAPeter Attia
Obviously they have mitochondria.
- SDSteven Dell
They do.
- PAPeter Attia
Obviously they have-- W- i- is there-- What distinguishes them? Do they have photoreceptors? Like, what makes them unique?
- SDSteven Dell
They are photo-- they're referred to as photoreceptors.
- PAPeter Attia
Okay.
- SDSteven Dell
And they have stacks of structures within them that are photosensitive and that causes a depolarization which-
- PAPeter Attia
So they work like channelopsins do?
- SDSteven Dell
They, uh, they-
- PAPeter Attia
They use a photon to create an action potential or to-
- SDSteven Dell
Correct. Once the photon hits that particular cell photoreceptor, then there's a change in the, the membrane and ions flow, and that's how a signal is generated.
- PAPeter Attia
Wow.
- SDSteven Dell
Yeah.
- PAPeter Attia
Okay. So all of that ion flow ultimately makes its way to the optic nerve?
- SDSteven Dell
Correct. That's right, and to the brain, and most of the visual processing is in the very back of your brain. Um, so that's-- And, and about half of the overall brain structure deals with vision in some capacity. And that's why, for example, when people have a stroke, there's almost always some component of visual involvement in a stroke. So you may have a droopy face on one side and then a limb is droopy as well, and then-- but if you map out the visual sphere, you will detect some deficit in the visual sphere from, from most strokes.
- PAPeter Attia
Now, uh, people who listen to this podcast have-- we've-- on various episodes we've got into the brain and people understand that I think there's sort of the brain stem, the most, you know, primitive piece of our brain that is basically responsible for autonomic function. You then have sort of this midbrain that sits on top of it that we call the sort of reptilian brain.
- SDSteven Dell
Mm.
- PAPeter Attia
A lot of emotion there. But of course, what in theory distinguishes us from all the other animals is this remarkable cortical piece that sits on top of it and is it-- how much of the visual processing is in that neocortex? Is it virtually all done there?
- SDSteven Dell
Yeah.
- PAPeter Attia
Is any part of it done in the midbrain?
- SDSteven Dell
Yeah, stuff like pupil responses.
- 39:37 – 46:06
Understanding human vision through an evolutionary lens
- PAPeter Attia
let's, let's talk about, uh-
- SDSteven Dell
Yeah
- PAPeter Attia
... let's talk about bow and arrow hunting, where you really... I mean, if you really wanna reduce the margin of error, you wanna be inside of 50 yards to be able to take that shot.
- SDSteven Dell
Sure.
- PAPeter Attia
So the way I always talk about this is animals have superpowers, and we just have to decide, as do we, we have superpowers, our greatest one being our intelligence, which allowed us to make the bow. [laughs]
- SDSteven Dell
Right.
- PAPeter Attia
Um, but I generally think of the three big senses, right? Which is the sense of vision-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... the sense of smell, the sense of hearing. And there's simply no comparison in sense of smell. We basically can't smell. Uh, we're, we're effectively useless creatures in nature.
- SDSteven Dell
Agreed, yeah.
- PAPeter Attia
Um, you know, they can smell us with... If they're downwind of us, they can smell us a mile away. Literally-
- SDSteven Dell
Wow
- PAPeter Attia
... one mile away, if the wind-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... moves from you to them, they're gone. You'll never get close to them.
- SDSteven Dell
Right.
- PAPeter Attia
Um, it turns out that the closest sense we have to our prey is vision.
- SDSteven Dell
Right.
- PAPeter Attia
It's the only thing where we're almost on par with them. Now, there are some animals that can see better than us. You know, if you... There are certain types of rams that if you break skyline within two miles of them, they'll see it.
- SDSteven Dell
And birds.
- PAPeter Attia
Yeah.
- SDSteven Dell
Yeah.
- PAPeter Attia
Um, but for the most part-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... like this is the one sense that we have-
- SDSteven Dell
Right
- PAPeter Attia
... that rivals the best.
- SDSteven Dell
Right.
- PAPeter Attia
Uh, i- is that because we both had to, as you said, be hunters and be hunted for such a large part of our evolution? Do you... Is that... I mean, this is sort of teleologic explanation I'm looking for, but...
- SDSteven Dell
Well, I think so, but think, just think about this for a moment. 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 at high noon in that same desert where there may be 200,000 lux illumination, you can still function and see well. So many, many, many-
- 46:06 – 50:42
Enhancing vision beyond 20/20
- PAPeter Attia
objects where you can't.
- SDSteven Dell
Interestingly, you know, I've operated on a number of Major League Baseball players, and for them, seeing the laces on the ball-
- PAPeter Attia
It's huge
- SDSteven Dell
... as hitters is enormous.
- PAPeter Attia
It's their career.
- SDSteven Dell
It is their career, and it's the difference between them hitting, you know, well or average. And, and some of these players that we've operated on have been 20/20 before they had surgery, but they wanted to be 20/15 or 20/10, and what that means is, you know, again, here's another nomenclature issue. What is 20/20 vision? Uh, 20/20 simply means that you can see at 20 feet what a, quote unquote, "normal person" can see at 20 feet. If you're 20/10, you can see at 20 feet what a normal person has to get 10 feet up to in order to see.
- PAPeter Attia
Yeah.
- SDSteven Dell
So 20/10 is better than 20/20. So some of these guys wanna be 20/10 or 20, you know, whatever it is, 20/15. We've been able to achieve that with modern forms of laser vision correction because-
- PAPeter Attia
Wait a minute. How is th- Isn't this now getting into the performance enhancing side of things? Isn't this kind of amazing?
- SDSteven Dell
You know, it's interesting.
- PAPeter Attia
I never even thought of this.
- SDSteven Dell
Yeah, for sure, and, and I had a discussion yesterday with a guy who owns a soccer team, and I said, "Have you ever had your players tested for their vision?" And he sort of froze and turned white, turned white for a second, and he just said, "It's so crazy you say that because we put them through this barrage of tests physically to see with their heart, their lungs, their kidneys, all that stuff. We didn't check their vision." And there are ways to boost human performance beyond 20/20. The theoretical limit of how well you could see is defined by essentially the pixelation of your retina, the spacing of the cells of those photoreceptors that we talked about earlier.
- PAPeter Attia
And does that vary from p- person to person?
- SDSteven Dell
It, it has to, but it's somewhere in the vicinity of about 20/08 or, or so. And so if you can have a sharp enough image, you could theoretically see better than 20/10, and the only way you can really achieve that is to remove some of the optical irregularities that we are all born with and somehow neutralize them along with the glasses prescription, and we can actually do that with laser vision correction currently.
- PAPeter Attia
So why would it be beneficial, I guess we'll talk about laser surgery, and maybe you'll wanna park this question until then.
- SDSteven Dell
Yeah.
- PAPeter Attia
Why would it be beneficial to an athlete who for understandable reasons needs the best vision possible to g- undergo laser corrective surgery versus just using contact lenses to To accomplish the same thing. Is that possible?
- SDSteven Dell
Yeah. So th- if you think about contact lenses, anyone who's ever worn contact lenses knows that when you put in a brand-new pair of contact lenses, you can see pretty well with them, and then you begin to regard that contact lens as a foreign object, so your body just begins to attack it, coat it with all sorts of i- immunological debris. You are susceptible to pollen, uh, dust, whatever it is that coats this, this, you know, formally pristine object. And let's say it ha- uh, there is correction for astigmatism in that contact lens, where its orientation is important. Every time you blink, that contact lens moves a little bit. All of those factors contribute to optical performance that is less than what you could achieve with spectacles or laser vision correction. So s- particularly soft contact lenses do a very, very good job, but they don't give you superhuman vision performance typically.
- PAPeter Attia
You know, it's funny, I experimented two years ago with a stronger prescription than normal-
- SDSteven Dell
Right
- PAPeter Attia
... to get me to 20/15 in my dominant eye for archery.
- SDSteven Dell
Sure.
- PAPeter Attia
Um-
- SDSteven Dell
Goofed up your near, though.
- PAPeter Attia
That's the problem.
- SDSteven Dell
Yeah.
- PAPeter Attia
I just abandoned it immediately-
- SDSteven Dell
Yeah
- PAPeter Attia
... after, like, six months of suffering-
- SDSteven Dell
Yeah
- 50:42 – 53:17
Astigmatism: definition, cause, and high prevalence
- PAPeter Attia
So let's now talk about how to correct these. Oh, I guess let's define an astigmatism, since-
- SDSteven Dell
Sure, yeah
- PAPeter Attia
... I don't know what that is yet.
- SDSteven Dell
Yeah, I, I mean, it's, it's when the eye is shaped like a football instead of a basketball.
- PAPeter Attia
And when you say the eye, d- which part of the eye specifically?
- SDSteven Dell
The cornea, the very front part of the eye typically. They're-
- PAPeter Attia
And how thick is the cornea, by the way?
- SDSteven Dell
It's about as thick as a credit card, like 500 microns.
- PAPeter Attia
Oh, that thick.
- SDSteven Dell
Yeah.
- PAPeter Attia
Okay.
- SDSteven Dell
Yeah, like 550 microns, something like that.
- PAPeter Attia
So half a millimeter.
- SDSteven Dell
Yeah, exactly right.
- PAPeter Attia
Yeah.
- SDSteven Dell
So half a millimeter. And it's typically that is the location of astigmatism. There can be astigmatism in the lens itself, the lens behind the pupil. But-
- PAPeter Attia
So you probably don't remember which one I have, do you?
- SDSteven Dell
I do.
- PAPeter Attia
Which one do I have?
- SDSteven Dell
You have corneal astigmatism.
- PAPeter Attia
That's the n- so that would be the-
- SDSteven Dell
That's the normal one
- PAPeter Attia
... more common one. Okay.
- SDSteven Dell
Yeah, it is very pedestrian. You're a very boring patient. But [laughs] the, the, uh, uh, the, uh-
- PAPeter Attia
So meaning, just to be clear-
- SDSteven Dell
Yeah
- PAPeter Attia
... I'm not perfectly shaped around here.
- SDSteven Dell
Spherical. Yeah.
- PAPeter Attia
I'm a bit oblong.
- SDSteven Dell
That's right, shaped like an egg or a, a football, an American football. Right?
- 53:17 – 1:04:58
Nearsightedness (myopia): causes, epidemic in children, and prevention strategies
- PAPeter Attia
you mean distance from-
- SDSteven Dell
Front to back.
- PAPeter Attia
Okay.
- SDSteven Dell
So anterior-posterior length of the eyeball. Primarily, that is the main driver as to whether you are 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. 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.
- PAPeter Attia
Let me make sure I understand that.
- SDSteven Dell
Okay.
- PAPeter Attia
Very long AP axis.
- SDSteven Dell
Mm-hmm.
- PAPeter Attia
[lip smacks] You're gonna have a real hard time seeing things far away.
- SDSteven Dell
Correct.
- PAPeter Attia
And is that because the further something is, the harder you have a time focusing all that light?
- SDSteven Dell
Well, let's talk about the genesis of this.
- PAPeter Attia
Okay.
- SDSteven Dell
Right? So if most of your work, most of your visual environment is close, then the image, the light rays from that close object are diverging, and so they are falling behind the retina of someone who's perfectly targeted for distance. So your 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. So-
- PAPeter Attia
Over what timescale?
- SDSteven Dell
Over a period of months. So if you take a young person And you exclusively have them perform near tasks. Their eye will grow longer so that those near objects are in perfect focus.
- PAPeter Attia
So if you could do an awful experiment-
- SDSteven Dell
It's been done
- PAPeter Attia
... you would take a child and not sh- put them in a white room where there's nothing that they can see that's far away, and just have them play with close objects that they can reach.
- SDSteven Dell
Yeah.
- PAPeter Attia
And you would put that kid into glasses as a child.
- SDSteven Dell
That's called society in 2021, is children looking at screens, near objects for hours on end and not going outside. There are two drivers of nearsightedness in the plastic developing human. Number one, uh, deprivation from outdoor light, and number two, near work. So for example, there have been cohorts of children, these, most of these studies have been done in Asia where there is an epidemic right now of myopia of astonishing proportions. I'm talking about 90% of the population is now nearsighted in certain Southeastern Asian cities. Um, when that becomes such a dominant phenotype, something is really oddly off. So-
- PAPeter Attia
Wow. So this really transcends evolution.
- SDSteven Dell
It trans-
- PAPeter Attia
Because you can change, if you can change something-
- SDSteven Dell
It's plastic
- PAPeter Attia
... in years or months-
- SDSteven Dell
In, within the... It's not evolutionary.
- PAPeter Attia
Yeah, it's just that-
- SDSteven Dell
It's, it's within the eye. It's w- it's adaptive-
- 1:04:58 – 1:20:07
Cataracts: impact of aging and how they can be repaired
- SDSteven Dell
tuned. Now, there's a whole host of other problems that come into play. Once you've outlived your genetic usefulness, you've reproduced and you've imparted your knowledge onto the next generation, you can go ahead and get cataracts because you're us-
- PAPeter Attia
Yep
- SDSteven Dell
... you're, you're done y- you know, genetically useful. Your us- utility is-
- PAPeter Attia
So the, the cataract is sort of like atherosclerosis if, functionally, which is it really, it's, it's the one thing that really has no bearing on your reproductive capacity but is otherwise inevitable to our species.
- SDSteven Dell
It seems to be fairly inevitable, uh, uh, to our species, and I've, as I mentioned earlier, I just haven't seen patients in their 70s typically that 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. Uh, maybe their visual needs are significantly reduced at that age. 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.
- PAPeter Attia
That's real interesting. Now, earlier you mentioned that we think that senescent cells, or at least the soluble secretory products of senescent cells, are probably playing a role in this.
- SDSteven Dell
Well, I think in the lens it's mostly that the lens proteins are degrading or becoming, uh, damaged over time, maybe with UV light. Because we know light exposure is certainly related to cataract formation, as are some of the other things that I mentioned, like glucose-
- PAPeter Attia
Mm-hmm
- SDSteven Dell
... going into the lens, uh, corticosteroid use. We don't know what it is specifically about trauma that causes a premature, uh, you know, lack, a loss of clarity of the lens proteins.
- PAPeter Attia
The trauma one's got me worried because I boxed for so long. I took a, way too many hits to the head. I hope that doesn't come back to... I mean, I've already been, I'm worried about that for other reasons, but-
- SDSteven Dell
Let's put it this way. The cataract would be the easiest thing to fix.
- PAPeter Attia
Yeah, yeah, yeah, yeah.
- SDSteven Dell
You know, that's, [laughs] you know, cataract surgery today is like a four or five-minute procedure, and it's astonishingly effective.
- PAPeter Attia
How often does one need to repeat that surgery?
- SDSteven Dell
Cataract surgery typically is not repeated. It's a once in a lifetime deal.
- PAPeter Attia
So you A- a- and what you're noticing is like you're wearing glasses that are dirty? Is that effectively what the patient with cataract is experiencing?
- SDSteven Dell
I think the first thing they notice is probably changes in their night vision, glare, halos, streaks around, you know, streaks off of lights at night, um, problems with contrast sensitivity for those who, uh, can appreciate that, loss of contrast. Um, those are really early signs of cataract formation.
- PAPeter Attia
So then l- the patient comes to you, they're 74 years old, uh, or let's say it's sooner. They're, they're 70 years old, and you s-
- SDSteven Dell
More like 64 or 54. Yeah.
- PAPeter Attia
Okay. And you're telling them, "Hey, Billy, you've got cataracts."
- SDSteven Dell
Right.
- PAPeter Attia
"We're gonna just ride this out until you tell me you've had enough"?
- SDSteven Dell
Yeah, typically we let the patient decide when it's the right time for them to have the surgery, um, once we determine that the cataract is visually significant. Uh, 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, because now the lenses, the implant lenses that we put in to replace the cataract, have advanced in function to the point that they can fix the near vision as well as the distance vision, as, you know, the astigmatism, the nearsightedness, the farsightedness, the presbyopia. All those things that we've been talking about, they're all correctable with artificial lenses that we put in the eye to replace the cataract.
- PAPeter Attia
Wow. But earlier when you talked about during your residency, the bread and butter was, one of the pieces of bread and butter of your, uh, practice would've been cataract surgery.
- SDSteven Dell
Right.
- PAPeter Attia
That didn't involve intraocular lenses, did it?
- SDSteven Dell
No, it did.
- PAPeter Attia
It did.
- SDSteven Dell
It did. And there's a, there's a fascinating history about the, the evolution of intraocular lenses. Uh, but back in those days, uh, the implant lenses that were put in were simply designed to give the patient good vision with spectacles, just to replace the cloudy lens with something that was in the ballpark of good distance vision.
- PAPeter Attia
Sorry, I need to take a step back-
- 1:20:07 – 1:27:50
Lens implants that can correct and improve vision
- PAPeter Attia
So if I came in and right now and I had a cataract-
- SDSteven Dell
Right
- PAPeter Attia
... what are you assessing microscopically to make it so, so it's... I'm getting the impression not everybody gets the same lens.
- SDSteven Dell
No, they do not. And some of these lenses are expensive, so, and they involve the patient having to pay some extra money to get it.
- PAPeter Attia
And more money gets you what?
- SDSteven Dell
I mean, I think the more money people pay, the more spectacle independence they get. In terms of optical quality, all the lenses are-
- PAPeter Attia
How much does a lens cost? Or pair, I guess, since you're doing both.
- SDSteven Dell
I mean, I- I'm the wrong person to ask, honestly. I don't even know.
- PAPeter Attia
But directionally, like if somebody has to pay out of pocket for one of these.
- SDSteven Dell
If they're getting just like regular cataract surgery and there is no attempt to get rid of spectacles, it's probably gonna be completely covered by their health insurance.
- PAPeter Attia
And if they're saying, "I want to go premium all the way, get rid of my glasses,"
- SDSteven Dell
It could be thousands of dollars out of pocket i- if they want to get rid of all their spectacle and, uh, dependence. And what patients will tell us is they'll say, "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, and then the vacation is over. But we find that patients value, as we pointed out earlier, their vision, they value it pretty highly, and their independence, I think, is really what they're trying to preserve.
- PAPeter Attia
This is, this is ama- I had no idea that when... Look at, look at how much I didn't know. I didn't know you were... I literally, this is how dumb I am. I thought cataract surgery is literally removing the sort of crud that's in the lens, and I don't know, I just naively assumed it would, like the good stuff would grow back.
- SDSteven Dell
Right.
- PAPeter Attia
I, 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.
- SDSteven Dell
That's right. And, uh, you know, so the technology has evolved to the point where you can actually correct those, those, uh, those spectacle requirements. Now, many of our patients don't really care about spectacle independence. They just wanna see well, and that's easy to achieve as well. Um, but as these lenses have gotten better, our capabilities have gotten better.
- PAPeter Attia
If I needed cataract surgery today-
- SDSteven Dell
Right
- PAPeter Attia
... knowing my diopter, the minus four-
- SDSteven Dell
Right
- PAPeter Attia
... minus three business with the slightest astigmatism, although I still haven't figured out how that's impacting my vision.
- SDSteven Dell
Right.
- PAPeter Attia
Um, I guess I sort of have it, just, but we'll come back to that. If, if you were gonna swap out my lens, would you be able to correct the deficit of my magnitude?
- SDSteven Dell
We could, yes. Yeah. Now, you know, the problem with a lot of these eyes is they're, they are attached quite firmly to people, [laughs] and sometimes the patient's set of expectations can be unrealistic in terms of what we can deliver. And so we have to really carefully educate them on, well, what can these lenses actually do? Am I gonna see like a perfect, uh, hunter at dusk while still be able, while still being able to read up close? And maybe the answer is yes, maybe the answer is no.
- PAPeter Attia
And can you tune it? Like for example, if I said, you know, "Steven, look, I don't care if I have to keep wearing contacts."
- SDSteven Dell
Right.
- PAPeter Attia
"I would love to not have to wear reading glasses."
- SDSteven Dell
Right.
- PAPeter Attia
'Cause if I'm gonna be honest with you, the reading glasses are a way bigger pain in my butt than contacts, 'cause I just put my contacts in in the morning and take them out at night.
- SDSteven Dell
Right.
- 1:27:50 – 1:30:14
Effects of eye trauma
- SDSteven Dell
right. That's right. In fact, if you violate that capsule-
- PAPeter Attia
The, the-
- SDSteven Dell
... of the lens, the lens immediately becomes cloudy. So, and here's an example. Let's say that-
- PAPeter Attia
Makes sense
- SDSteven Dell
... you talk about trauma. So a typical scenario is, uh, somebody is, uh, working with a weed eater or whatever, a, a weed whacker.
- PAPeter Attia
Weed whacker, yeah.
- SDSteven Dell
Yeah. And, and a piece of, a, a shard of rock or glass or something goes through the cornea and embeds itself in the lens. And it 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, inflammatory cells become, uh, uh-
- PAPeter Attia
You violated the privileged site.
- SDSteven Dell
It's no longer privileged, and within days you start to see a cataract.
- PAPeter Attia
And they need a new lens.
- SDSteven Dell
They need a new lens, for sure.
- PAPeter Attia
Do they need a new cornea, by the way?
- SDSteven Dell
Well, they sometimes do. Uh, 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. And, and, and some, some of these objects can be left alone. But, um, if the cornea has been damaged sufficiently that it's no longer able to transmit a clear image, then it has to be replaced.
- PAPeter Attia
Wow. So, um, let's talk a little bit about corneal pathology. So, um, everyone's probably heard about corneal abrasions. Uh, it's a very important reason I reme- it's one of the few things I remember, right? In surgery you always tape the patient's eyes shut-
- SDSteven Dell
Right
- PAPeter Attia
... because, you know, you don't want an eyelid flipping open in the middle of surgery and nobody's paying attention, and a drape-
- SDSteven Dell
Right
- PAPeter Attia
... is running over the eye-
- SDSteven Dell
That's right
- PAPeter Attia
... and scraping the cornea.
- SDSteven Dell
Yeah.
- PAPeter Attia
Um, is that the biggest insult that we think about for the cornea?
- SDSteven Dell
I mean, that's probably one of the more common ones. If you think about that eye that's been left open in surgery while a patient is asleep and not blinking, that's sort of the extreme version of dry eye, where the, the, the cornea has completely dried out. And even if you weren't to, if you were, if you didn't abrade the cornea, those epithelial cells would be so damaged by exposure just by not, uh, being continuously bathed in, in tears that they would be severely damaged.
- 1:30:14 – 1:36:54
Corneal abrasion from ‘dry eye’: causes, treatment, and prevention strategies
- SDSteven Dell
Uh, so dry eye is intimately related to corneal abrasion because you lack the lubrication that normally takes place to prevent that type of thing.
- PAPeter Attia
And, and how much of a, of an issue is that in our society?
- SDSteven Dell
Dry eye?
- PAPeter Attia
Yeah.
- SDSteven Dell
Oh, it's enormous. It's, uh... I mean, it's... If you think about the things that cause dry eye, um-
- PAPeter Attia
I mean, there's obviously lots of medications that do it through-
- SDSteven Dell
For sure
- PAPeter Attia
... anticholinergic side effects.
- SDSteven Dell
Absolutely. But think about all the antihistamines.
- PAPeter Attia
Mm-hmm.
- SDSteven Dell
Um, you know, hormonal influences are profound in terms of dry eye. Anything that causes dry mouth, uh, can also cause dry eye. In that sense, autoimmune conditions can cause dry eye, so Sjogren's, rheumatoid arthritis.
- PAPeter Attia
Yep.
- SDSteven Dell
All of the connective tissue diseases have a dry eye component to them. Perturbations of thyroid, uh, metabolism cause dry eye. Um, but you know, a lot of women suffer from dry eye because they're... I think it's mostly the influence of, uh, honestly, a lack of testosterone that is probably most intimately linked to, to dry eye, but we see women on hormone replacement therapy that have miserable dry eye.
- PAPeter Attia
So meaning even... So you think the addition of estrogen and progesterone post-menopause could be an issue, or do you think it's still just the lack of testosterone that you-
- SDSteven Dell
I think it's the lack of testosterone because-
- PAPeter Attia
Why, why do you think that?
- SDSteven Dell
I think it has to do with the health of the epithelial cells on the conjunctiva. Um, but there may be also influences on the, the, the secretion of tears from the lacrimal gland as well. Um- But dry eye is, I mean, it's... I don't want to say it's universal in patients who are over a certain age, but it's extremely common.
- PAPeter Attia
So what type of eye drops should we be using? How do we apply them?
- SDSteven Dell
Well, it, it really depends on the type of dry eye that you have, believe it or not. Because there are, um, uh, you-- We think of tears as just saltwater, but that's really not what it is. It's really an, an emulsion of lipids and-
- PAPeter Attia
Hmm
- SDSteven Dell
... uh, mucin and all sorts of immune modulators and, uh, and antibodies and all sorts of things in this soup. Some of it is just what we refer to as the aqueous component of tears, really just the saltwater. Um, but the, uh, sebaceous glands that are in the eyelids, we call them meibomian glands at, at the little where the lashes come out of the skin. Um, though the, 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, um, all sorts of things that cause meibomian gland dysfunction. Some of that relates to diet, and some people believe that a, a, a diet high in saturated fats is more likely to cause meibomian gland dysfunction. Um, certainly colder weather, like all... like, uh, the secret- like the meibomian, like the sebaceous glands in your skin respond better to sunlight, to heat. Um, in a cold environment, those can become plugged up and bacteria can build up along the eyelid margin, causing inflammation, and when there's inflammation, the, the, the, the lacrimal gland shuts down even more. So there are-- dry eye is really multi, uh, has, has... it's, uh, it's got, uh, a, a number of different causes.
- PAPeter Attia
Now, when I think about eye drops, I, I think about sort of the, the dropper that you try to get in your eye and you-
- SDSteven Dell
Right
- PAPeter Attia
... never get it-- at least I can never get it in my eye-
- SDSteven Dell
Right
- PAPeter Attia
... because I end up blinking all the time. So then I-- you try and drop it into your, the corner-
- SDSteven Dell
Into the corner, yeah
- PAPeter Attia
... the corner and then let it sort of... But then I've also seen like the mist, right?
- SDSteven Dell
Yeah.
- PAPeter Attia
So, so d- tell me about the different ways that one even applies these-
- 1:36:54 – 1:44:32
Sunglasses for eye protection
- PAPeter Attia
Let's go back to light for a minute.
- SDSteven Dell
Yeah.
- PAPeter Attia
So I've got some friends who are so fanatical about the importance of light that they never wear sunglasses. Um, now I... and I, and I'm, I'm kind of-- there's a part of me that thinks light is, wow, it's gotta be really important. I, I think about, you know, all the time I get outside in the light, it's great, it's great.
- SDSteven Dell
Right.
- PAPeter Attia
But I also like wearing sunglasses-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... 'cause there's a part of me that's sort of afraid that-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... too much UV light is damaging. So what's the balance of, of sunglasses versus not? And w- I wanna talk about polarized glasses. Are they-
- SDSteven Dell
Right
- PAPeter Attia
... do they matter, and all that kind of stuff.
- SDSteven Dell
Yeah, I mean, clearly there's a dose-related phenomenon here. You know, too much light is bad, too little light is bad. What's the right amount? I tend to recommend sunglasses for our patients. Um, let's start with just the most obvious one. The most common site of skin cancer, the lower lid. Lots of basal cell, squamous cell carcinomas. Sunglasses certainly reduce the incidence of that. Uh, then we look at the photo aging of the lens itself. I think it's not a bad thing to delay the onset of cataract. Um, and then the retina, macular degeneration. I think there's pretty cl- clear evidence that UV exposure, uh, particularly of the magnitude that you can get outside, uh, is associated with an elevated risk of age-related macular degeneration.
- PAPeter Attia
Now, do we see this in hunter-gatherers who have otherwise amazing habits, and therefore tend to be relatively privileged from, uh, uh, optical-
- SDSteven Dell
Yeah
- PAPeter Attia
... pathology?
- SDSteven Dell
So, so the confounding variable there is that, um, Northern European ancestry is a risk factor for macular degeneration, probably because of the lack of pigment.
- PAPeter Attia
Hmm.
- SDSteven Dell
Because that pigment is protecting that very vulnerable, uh, vascularized component of the back of the eye.
- PAPeter Attia
Oh, wait. So the darker your eye, the more protected you are?
- SDSteven Dell
Absolutely, in the same way that your skin is more protected-
- PAPeter Attia
Got it
- SDSteven Dell
... with more melanin. So light-eyed patients have more light getting in from the front of the eye, and-
- PAPeter Attia
So their iris literally blocks less light hitting the lens?
- SDSteven Dell
Yes. And their, the, the retina has less pigment behind it.
- PAPeter Attia
Hmm.
- SDSteven Dell
And so 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. Um, but if you live near the equator or your ancestry is from that area, then you're gonna have more pigment, um, and from an evolutionary standpoint. But, um, I understand the fanaticism about wanting to have lots of blue light or, you know, bright light, but I think that it probably is fanaticism. I d- I don't think that, uh, you know, at least if your goal is to reproduce, teach your children until they're 15 and then die, then get all the light you want. But if your goal is longevity or the, the postponement of senescence, certainly ocular senescence, I think it makes sense to protect your eyes from UV light.
- PAPeter Attia
So for example, like, let's, so you, you came over here today where it's middle of the day in Austin.
- SDSteven Dell
Yeah.
- PAPeter Attia
It's a typical Austin beautiful sunny day. You're driving with sunglasses when you came over?
- SDSteven Dell
Oh, for sure. Absolutely, 100%.
- 1:44:32 – 1:48:27
Solutions to correct nearsightedness
- PAPeter Attia
Okay, so let's now go back to the standard situation of nearsightedness. So person comes in, they're nearsighted.
- SDSteven Dell
Right.
- PAPeter Attia
Um, decision one is I'm gonna correct this with glasses versus contacts. We'll start to talk about corrective surgery in a moment.
- SDSteven Dell
Yeah.
- PAPeter Attia
Um, do you nudge people one way or the other? I mean, I, I wore glasses for the first four years that I needed pr- corrective lenses, um, so that meant basically college. Trying to think in med school. I think by med school I was wearing contacts. By residency, I went back to glasses-
- SDSteven Dell
Right
- PAPeter Attia
... because the call, you know, you're, you're-
- SDSteven Dell
Sure
- PAPeter Attia
... just, you just couldn't be predictable about when you were gonna put them in. So I did all-
- SDSteven Dell
Right
- PAPeter Attia
... of residency in glasses, and then since that time I've been 100% contacts.
- SDSteven Dell
Yeah, it's funny 'cause we'll, like, we'll see residents or fellows or whatever, and they come in and on their one day off, and they're seeing one of our optometrists, and, "When did you last have your contacts out?" And they're like, "I think it was June 30th, right before my, uh, internship started four months ago." You know?
- PAPeter Attia
Oh, God.
- SDSteven Dell
You know, that sort of thing. It was, uh... A- and, and so as you know, residents are notoriously bad about their own, uh, health hygiene and, and 'cause you're so busy. But, uh, uh, to answer your question more directly, I don't really see patients for regular eye exams myself, but, uh, so the people who see me are seeking surgery-
- PAPeter Attia
Okay
- SDSteven Dell
... already. But in terms of, hey, I'm at a cocktail party and someone says, "Should I wear glasses or contact lenses or spectacles?" Like, well, you know, the safest thing you can do is wear spectacles for sure.
- PAPeter Attia
Wait. Do you use glasses and spectacles interchangeably, that term?
- SDSteven Dell
Yes. When I say spectacles, I'm-
- PAPeter Attia
Okay. Okay
- SDSteven Dell
... I'm-
- PAPeter Attia
That's what I thought so, yeah
- SDSteven Dell
... referring to glasses to distinguish them from stuff you drink water out of. [laughs]
- PAPeter Attia
[laughs]
- SDSteven Dell
So, so yeah, spectacles is our, is the term of art for, uh-
- PAPeter Attia
Very well
- SDSteven Dell
... for, uh-
- PAPeter Attia
Very well
- SDSteven Dell
... for glasses.
- PAPeter Attia
[laughs]
- SDSteven Dell
Yeah. Um, yeah. So if you, uh... Yeah, you were thinking of some sort of exotic type of-
- 1:48:27 – 2:05:41
Laser eye surgery—photorefractive keratectomy (PRK)
- SDSteven Dell
that's a whole other story. Right.
- PAPeter Attia
So let's talk about the advent of, of laser eye surgery.
- SDSteven Dell
Right.
- PAPeter Attia
So I think everybody listening to this has heard of LASIK.
- SDSteven Dell
Yes.
- PAPeter Attia
Most people probably haven't heard of PRK-
- SDSteven Dell
Right
- PAPeter Attia
... um, which we'll talk about.
- SDSteven Dell
Mm-hmm.
- PAPeter Attia
When did... PRK came along first, I assume.
- SDSteven Dell
Yeah, a little bit earlier, yes.
- PAPeter Attia
And that was when, in the '90s?
- SDSteven Dell
Right. So the, the approvals for PRK and LASIK were in the mid-'90s, 1995, 1996. The first procedures were actually done in, uh, the first procedure was PRK-
- PAPeter Attia
Yeah
- SDSteven Dell
... and it was done in New Orleans. And, um, I happened to be, uh, in training there, uh, in New Orleans, w- and this was performed by a physician called Marguerite McDonald, and she did the very first, um, treatment on a, on a human eye. The way this came about was that excimer lasers, which are the kind of lasers we use in LASIK and in PRK, which stands for photorefractive keratectomy, excimer lasers are and were used to etch microchips. And an engineer at IBM realized that you could change the curvature or you could 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, the, the tissue could be etched or, uh, or cut- And because it generated no heat, there was no immune response generated typically, uh, so that these incisions or whatever the, it was, they would heal without scarring. And I can remember vividly looking at the very first patients that were in, uh, an FDA clinical trial that had PRK, and I was astonished that you could look at them under a microscope, and you could not detect that surgery had been done. 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. [smacks lips] So the first eyes were treated in '89, and then that led to FDA approval, uh, in '95.
- PAPeter Attia
And the treatment in '89 was part of clinical trials, I'm assuming.
- SDSteven Dell
For sure.
- PAPeter Attia
Yeah.
- SDSteven Dell
It was part of a clinical trial.
- PAPeter Attia
So let's explain what PRK does-
- SDSteven Dell
Right
- PAPeter Attia
... before LASIK.
- SDSteven Dell
Yeah, so the way it works is that you, uh, you have 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. The cornea in that person is a little bit too steep to focus the light perfectly on their retina. Another way of looking at it is that their-
- PAPeter Attia
And again, the cornea is about two millimeters thick?
- SDSteven Dell
No.
- PAPeter Attia
Or the cornea's half a millimeter.
- SDSteven Dell
It's about a half a millimeter thick.
- PAPeter Attia
Okay.
- SDSteven Dell
It's about 500 microns, maybe a little more. Um, so either the cornea is a little too steep or the eyeball is a little too long, probably a little of both. We can't change the length of the eye.
- PAPeter Attia
By the way, the length of the eye is the one that we talked about being somewhat malleable during-
- 2:05:41 – 2:16:01
Laser eye surgery—LASIK
- SDSteven Dell
but you wouldn't have 20/20 vision at that point.
- PAPeter Attia
Mm-hmm. So LASIK, the only thing I know about that is there's a flap involved.
- SDSteven Dell
That's right.
- PAPeter Attia
So presumably you're not shaving off the epithelium, you're cutting a flap, and how much of that tissue you take off determines the shape of the new-
- SDSteven Dell
Right
- PAPeter Attia
... cornea when the flap comes back?
- SDSteven Dell
Right. So sa- so the laser that does the vision correction, all the little distortions, the nearsightedness, the astigmatism, that's all the same laser. So that part of the procedure is identical. But instead of doing that on the surface of the eye, now we're using a step before that where we create a flap in the cornea using a different type of laser. So we use a femtosecond laser to create about a, let's say 100 micron flap. So we are now under the epithelium.
- PAPeter Attia
So you've taken 20% of the cornea up.
- SDSteven Dell
That's right, about 20% of the cornea up. And now think of it as in our analogy where we were sanding a wooden eye before, now think of the cornea as a book, and in PRK, I'm removing the first 10 pages of the book.
- PAPeter Attia
Here you're opening the cover page, I think.
- SDSteven Dell
Now I open it to page 100 and I'm taking out 100 through 110.
- PAPeter Attia
Yeah.
- SDSteven Dell
And then I close the book. The beauty of LASIK is that because that, that, that tissue removal is sequestered under that flap, the body doesn't perceive that anything has been done. So it's very typical for patients who have LASIK to be 20/20 the next morning. And so that's the appeal of that procedure.
- PAPeter Attia
And, and that's why LASIK was developed post-PRK, presumably as a way to get around the healing process of PRK?
- SDSteven Dell
Yeah, that was sort of a technological race, and the way it developed was interesting, and some of it was, uh, uh, uh, uh, in pursuit of more rapid visual recovery.
- PAPeter Attia
So what percentage of corrective eye surgery in the United States today is PRK versus LASIK? I assume the lion's share is LASIK.
- SDSteven Dell
Yeah. I think it's, it's, it changes, but it's probably about 80 to 85% LASIK. And not to confuse things, there's another procedure called SMILE, which is a very small but, but perhaps growing segment of the market, and we can talk about that in a sec. But the lion's share of it is, is LASIK. And there is a, but a significant chunk PRK. And we actually-
- PAPeter Attia
Are there more risks in LASIK than PRK?
- SDSteven Dell
Well, the risks are, are different because the risks of infection with LASIK are lower because you don't have this open-
- PAPeter Attia
You don't take the epithelium away.
- SDSteven Dell
That's right. But you introduce another step in the procedure where you now have a flap, and that flap can, you know, if, if it's not performed correctly, that can lead to problems. I think there is a little bit more dry eye issue with LASIK compared to PRK as well because when you create that flap, the way tearing works is that a signal from the front of the eye goes to the lacrimal gland, which then secretes tears. If you create a flap-
- PAPeter Attia
It cuts out that innervation
- SDSteven Dell
... you temporarily sever some of the nerves that are sending the signal, and eventually over time, those nerves typically regrow back and you reestablish that r- uh, feedback mechanism. But I think you get more dry eye with LASIK than with PRK and for longer. Um, that is a controversial statement. There are people who have data to show that they're equal, but I think they both result in temporary dry eye in most patients. Some patients have dry eye for really long periods of time after both procedures, but the majority of patients are kind of back to their baseline in about probably 60 to 90 days.
- PAPeter Attia
What about night vision or low light vision?
- SDSteven Dell
Yeah. So that's fascinating. There, in the early days of LASIK and PRK, the weakest part of vision was night vision, and that was because the shape of the treatment that we did and the diameter that we treated was limited, so we couldn't really treat the peripheral part of the cornea that comes into play when your pupil gets big. So if you are treating a central part of the cornea that is smaller than a big pupil at night, you're gonna see halos from that untreated peripheral part of the cornea. Over the last like, I don't know, 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 we find to be pretty unusual with laser vision correction.
- PAPeter Attia
Is there a difference in the cost of these procedures?
- SDSteven Dell
Uh, I mean, for us, no, but I'm sure there, there are some surgeons who charge more for one than the other. Um, the, the added step of LASIK adds some cost, but PRK has more postoperative care, frankly-
- PAPeter Attia
Mm-hmm
- SDSteven Dell
... um, because it requires more visits to, to see these folks, but we, we price them the same.
- PAPeter Attia
What are the, uh... And, and how much does it cost, by the way? I mean, it's direction- uh, it's probably come down a lot in 20 years, right?
- 2:16:01 – 2:18:02
Laser eye surgery—small incision lenticule extraction (SMILE)
- PAPeter Attia
And then you mentioned this SMILE procedure.
- SDSteven Dell
Yeah.
- PAPeter Attia
I haven't heard of that. What is that?
- SDSteven Dell
Yeah, it, you know, it's an interesting procedure. It's using a single laser, a femtosecond laser, and this is... I, I want to go back to the book analogy, where we opened the book to page 100. Well, imagine if you could somehow create a little tunnel down to page 100 and snatch out pages 100 through 110 while keeping the incision really tiny and perform it through a very small keyhole procedure. Um, that procedure has gained some traction outside the US and in the US.
- PAPeter Attia
Hmm.
- SDSteven Dell
Um, it seems to be an effective procedure. I don't, I have-
- PAPeter Attia
What problem is it solving, given how effective LASIK is?
- SDSteven Dell
I would say the problem it was designed to solve was dry eye.
- PAPeter Attia
Oh, okay.
- SDSteven Dell
But I think the problem it really solved, especially outside the United States, was needing two lasers versus one. So maintaining and-
- PAPeter Attia
But you could do one with PRK.
- SDSteven Dell
You could do one with PRK, but then you have the-
- PAPeter Attia
The, the long... So it's, yeah
- SDSteven Dell
... the, the, the prolonged, you know, recovery time. So the idea was could you get LASIK-like velocity of return of vision-
- PAPeter Attia
With a single laser
- SDSteven Dell
... with a single laser.
- PAPeter Attia
And maybe along the way, reduce dry eye.
- SDSteven Dell
Yes. There are pros and cons to SMILE. Uh, you know, s- the technology is evolving. I have not seen any data that shows that SMILE is in any way, uh, better than LASIK or even equal to LASIK, frankly. Um, but it seems to be a very good procedure. Uh-
- PAPeter Attia
Are you doing it as well?
- SDSteven Dell
I am not performing SMILE, and doesn't mean that I won't in the future. And there are a number of competing second- and third-generation versions of SMILE that will come on board, and if one of them ever rises to the point where I think it's better than what we're doing, we'll offer that.
- 2:18:02 – 2:24:35
Glaucoma: definition, causes, symptoms, and care
- PAPeter Attia
Um, we didn't talk about glaucoma.
- SDSteven Dell
Yeah.
- PAPeter Attia
Yet I know every time I go to an optometrist or even when I came and saw you, you... I, is that the one where you blow the air at my eye?
- SDSteven Dell
Well, that's sort of a, a-
- PAPeter Attia
Well, that's just an intraocular pressure test
- SDSteven Dell
... that's a way of measuring the intraocular pressure that we don't use, but it, it has the advantage of not requiring the patient to be touched with anything. So you can indent the cornea with a known amount of force from an air puff and look at how it optically deforms. Uh, the disadvantage to the air puff, and it's not really considered a, a, I don't think, a gold standard of measuring pressure, is that if you blink really quickly and squeeze, then you can have a false reading-
- PAPeter Attia
Yeah
- SDSteven Dell
... with that type of air puff tonometry. And we, we, we typically don't use that.
- PAPeter Attia
How do you measure intraocular pressure?
- SDSteven Dell
We measure it with two ways, both of which indent the cornea, physically indent the cornea after you-
- PAPeter Attia
So that's why you anesthetize the-
- SDSteven Dell
After you anesthetize the eye with a known amount of force, and then you look at the amount of force required to cause a certain amount of, of indentation.
- PAPeter Attia
And what's the definition of glaucoma?
- SDSteven Dell
Well, glaucoma is probably about 100 different diseases, honestly, but they all share the final common pathway of damage to the optic nerve, the nerve in the back of the eyes, the cranial nerve that you mentioned at the beginning, um, that is somehow related to pressure. Uh, so 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.
- PAPeter Attia
And, and the symptoms of glaucoma, are they all the s- I mean, is it always some change in vision? Is that what would bring someone to attention-
- SDSteven Dell
Yeah
- PAPeter Attia
... if they weren't getting a screening test?
- SDSteven Dell
It's, it's funny, you just sort of, like, triggered a memory of mine. I had a patient, I was, I was in training years ago, and, and I, I was explaining to a patient that, you know, glaucoma is totally, uh, has no symptoms at all. Um, you wouldn't notice it at all. And, and yet if we don't find it, it could be really bad. And the patient said, "Well, if it has no symptoms, what do I care?" You know, like, what's the point? And what I should have said was, "It has no symptoms-
- PAPeter Attia
Until it does
- SDSteven Dell
... until the very end."
- PAPeter Attia
Yeah.
- SDSteven Dell
So and what happens is that your peripheral vision is damaged, and most people will not detect A, a, a slight reduction in their peripheral vision, particularly if it's segmental. There's just one little area off to the side that they're, that they can't see, particularly if the other eye is covering for that area. Um, but as glaucoma progresses, it can affect central vision, and then it becomes symptomatic.
- PAPeter Attia
How much of a problem is this in the United States, first of all, and then in the rest of the world?
- SDSteven Dell
Well, luckily, glaucoma has become much more treatable. So the pharmacological management of glaucoma has gotten way better, and there are numerous laser procedures that can treat glaucoma and what are referred to as minimally invasive glaucoma procedure, or it stands for, you know, MIGS, minim- minimally invasive... Uh, basically the, uh, the management of this has gotten way, way better. And-
- PAPeter Attia
What, what are like the, what's the 80/20 of this? What, 80% of them are caused by what, basically?
- SDSteven Dell
Yeah. So 80, 80% of them are caused by what we refer to as garden variety, chronic open angle glaucoma, which means that it's n- the, the, 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 as a result.
- PAPeter Attia
The vitreous fluid?
- SDSteven Dell
No, it's the aqueous fluid.
- PAPeter Attia
And what causes that? Is that endocrine? Is that-
- SDSteven Dell
That's-
- 2:24:35 – 2:29:11
Tips for preserving eye health
- PAPeter Attia
to summarize, uh, you know, again, we think about kind of the longevity of the eye as a pretty important thing, right? If you want to figure out a way to live to 100-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... you, we, we spend a lot of time thinking about, well, you've got to really, really delay the onset of atherosclerosis. You have to have a very aggressive strategy around the mitigation of cancer, Alzheimer's disease, and all these things.
- SDSteven Dell
Right.
- PAPeter Attia
But it's these other things, teeth, ears, and eyes, that I don't think get enough attention, right? I mean, it's, you don't want to get to be 100 and have no teeth, and you don't want to get to be 100 and be deaf, and you don't want to get to be 100 and be blind.
- SDSteven Dell
Yeah, those all sound bad.
- PAPeter Attia
Yeah. So I mean, the things I'm picking up, unfortunately for many of us listening to this, we can't go back and change what we did as kids.
- SDSteven Dell
Mm-hmm.
- PAPeter Attia
Uh, we can certainly make a change in our kids, so we can make sure that they are outside in natural sunlight.
- SDSteven Dell
Right.
- PAPeter Attia
Um, I don't put sunglasses on my kids. I don't... Should I be doing that?
- SDSteven Dell
Yeah, I mean, probably. You know, it's, trying to get a kid to wear sunglasses is tough. I-
- PAPeter Attia
We gotta come up with better toys. Like, my kids love trains, so if I could figure out a way to tell them that wearing sunglasses was train-like-
- SDSteven Dell
Right
- PAPeter Attia
... this would be good.
- SDSteven Dell
Yeah. I, it's tough. I mean, you see kids who are snow skiing, for example, and they're, uh, they should be wearing goggles because those have built-in UV-
- PAPeter Attia
Yep
- SDSteven Dell
... UV protection. Um, so that typically works, you know, for that type of thing. But gosh, when they're water-skiing, they certainly can't wear glasses. If they're swimming, they can't wear sunglasses. Um, there's a certain-
- PAPeter Attia
Although goggles these days are pretty good.
- SDSteven Dell
That's true.
- PAPeter Attia
From what I've heard, yeah.
- SDSteven Dell
Yeah. I've, that's, it's hard to get my kids to wear goggles, but you know, there's a certain amount of just UV exposure I don't think it's possible to avoid.
- PAPeter Attia
So the trade-off is-
- SDSteven Dell
Yeah
- PAPeter Attia
... when in doubt, keep them out.
- SDSteven Dell
Yeah. You know, hats are important as well. We didn't really talk about that.
- PAPeter Attia
Yeah.
- SDSteven Dell
You know, I think that that's a very good and effective way, but it's not enough, 'cause a certain amount of light bounces off-
- PAPeter Attia
Yeah
- SDSteven Dell
... and hits the bottom of your cheek and goes right into your eye. So it's-
- 2:29:11 – 2:32:41
Screen time and eye health
- PAPeter Attia
We didn't really talk explicitly about screen use.
- SDSteven Dell
Yeah.
- PAPeter Attia
Is there... I mean, you talked about it a little bit in that study in Asia-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... where... But I don't know if that was specific to screen use or just could've been just as much reading or-
- SDSteven Dell
Yeah, it was not specific-
- PAPeter Attia
... playing with tinker toys.
- SDSteven Dell
Yeah, it wasn't specific to screen use. And-
- PAPeter Attia
So what do we know about phones specifically and computers?
- SDSteven Dell
Yeah. So, you know, this is a, a super interesting obviously topic and, and, uh, everything from people ask me about blue blocking glasses. They ask about w- am I damaging my eyes? Am I gonna get macular degeneration 'cause I'm looking at a computer screen for 10 hours a day? I'll start with the easy ones. Uh, the amount of UV radiation coming off of screens is sufficiently low that there has been no evidence at all that it's gonna cause macular degeneration, um, in the same way that you can't get a sunburn from a screen. I mean, the amount of blue light that you get from going outside is many, many, many orders of magnitude greater than what you can get from screens. Um, but I do think that blue light can mess up your circadian rhythm. And, you know, it's if you take someone and expose them to blue light at noon, that's great. If you expose them to that at 11:00 PM and then you try to go to sleep, that's messed up. It's almost like we're running this gigantic experiment with humans where, uh, think about like you ta- you have a turtle. Let's say you take a species of turtle that spends 90% of its time in the water, 10% on land, and we take that and flip it. Now it's 10% in the water. And then we look at these turtles and we think, "There's something weird going on with these turtles." Yes, they're surviving, but we're, we've got them 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. So, you know, I really try to limit-
- PAPeter Attia
But there's not, it's not clear that it's damaging their eyes per se.
- SDSteven Dell
It's not damaging their, their retinas or they're giving them cataracts, but I think it's messing up circadian rhythms. So-
- PAPeter Attia
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, which is the stimulation.
- SDSteven Dell
Right, you're thinking.
- PAPeter Attia
Like it's, it, it's... Yeah. I, I mean-
- SDSteven Dell
You know
- PAPeter Attia
... there seems to be a difference between watching TV and checking email before bed. Maybe none of them are... Maybe neither are ideal, but one seems demonstrably worse, at least for me.
- SDSteven Dell
Yeah, I think that's pretty universal. People feel that way, that passive watching a TV is different than, "I'm gonna... I wonder where Winston Churchill is buried." You know, you go down some wormhole and you're just, you know, you're just seeking information that takes you on these journeys. But, um, one thing I do, I do have software embedded in all of my, uh, PCs that changes the color temperature.
- PAPeter Attia
Like f.lux or something like that?
- SDSteven Dell
I love f.lux.
- PAPeter Attia
Yeah.
- SDSteven Dell
I, I, you know, I... And f.lux is free, by the way, I think for end users and it, it will take the blue light sequentially out of your monitor as the day goes on, as the evening goes on-
- PAPeter Attia
Yeah
- SDSteven Dell
... to the point that it's like super amber, uh, as you get ready to go to bed. I, I really think
- 2:32:41 – 2:34:11
Contact lenses: good hygiene and considerations
- SDSteven Dell
that's great.
- PAPeter Attia
Anything else we should be thinking about? I mean, the big takeaways for me have been the importance of sunglasses, artificial tears- Taking your contact lenses out as frequently as possible, right? So don't, don't sleep in them and stuff like that. Um, I know it's not your field, but do you have a point of view on daily versus the ones... I mean, it just seems to me dailies, if you can afford them, make more sense than the two-week ones that you have to wash every night.
- SDSteven Dell
Yeah. So, you know, I think the most important thing is that you just get them out of the eye. We really don't like extended wear contact lenses, so whatever type of contact that is. Um, w- as eye surgeons, we tend to see a selected sample of patients who are the problems, the people who have sight-threatening infections from sleeping, typically, in contact lenses. So yes, I realize there are millions of people who sleep in their contacts and don't get infections, but the people who end up in my, uh, you know, office have had problems, and some of them quite devastating problems. So I'm not a big fan of, of sleeping in contact lenses in general, but if you're going to sleep in contact lenses, I'd rather they be a perfect, pristine, new pair every single time, and get them out as, as quickly as you possibly can. So yeah, I-
- PAPeter Attia
Talked about eye protection.
- SDSteven Dell
Yeah.
- PAPeter Attia
Can't... Uh, again, I think we're a little more aware of that now than when we were kids.
- 2:34:11 – 2:36:48
A bonus benefit from repairing cataracts
- PAPeter Attia
Um, I, the other thing, takeaway for me is not to be so afraid of cataracts. They're inevitable, and you can actually, there's a, there's a, 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.
- SDSteven Dell
It is interesting that we s- w- once word got out in the community that this was something that could be done, y- you do see people coming in asking for cataract surgery, I think a little bit sooner than they otherwise would because they know that this added benefit is a, is a potential possibility. Um, so and, uh, you know, in the old days when we did not have intraocular lenses, or the generation a couple eye surgeons before me did not have intraocular lenses, you'd have to wear these, what were called cataract glasses, these super thick lenses that were very, very powerful and magnified everything and didn't really work all that well optically. So in that context, people-
- PAPeter Attia
Wait, you wore those post-cataract?
- SDSteven Dell
Post-cataract, yeah, 'cause there were no implant lenses.
- PAPeter Attia
Oh, wow.
- SDSteven Dell
And your prescription was typically about a plus 10. So you know that a minus 10 is a very-
- PAPeter Attia
Yeah. So there's-
- SDSteven Dell
... very nearsighted
- PAPeter Attia
... these, these people can't see without these glasses.
- SDSteven Dell
That's right. And so-
- PAPeter Attia
These are like the Coke bottles
- SDSteven Dell
... that, and I don't even know if people-
- PAPeter Attia
That's where glasses and spectacles meet
- SDSteven Dell
... do people even know what Coke bottles are anymore?
- PAPeter Attia
[laughs]
- SDSteven Dell
So the bottom of a Coke bottle-
- PAPeter Attia
Yeah
- SDSteven Dell
... is a really thick piece of glass, and this would magnify your eyes and make your eyeballs look enormous.
- PAPeter Attia
Yep.
- SDSteven Dell
And then you would have this, all sorts of optical distortions, because it's very hard to make a super powerful magnifying glass that you-
- PAPeter Attia
With a long enough focal length that you can-
- SDSteven Dell
With, without peripheral distortion.
- PAPeter Attia
Yeah.
- SDSteven Dell
And so you, in that context, would put off cataract surgery as long as humanly possible. So that's really not the case.
- PAPeter Attia
Is cataract surgery one and done? I mean, uh, you said it is, it should be.
- SDSteven Dell
Mm.
- PAPeter Attia
But do people ever need reoperations?
- SDSteven Dell
I mean, it's not unheard of where someone will have an implant lens put in that isn't functioning the way it should, and that can be replaced.
- PAPeter Attia
Is it difficult to get the old lens out, since you can't use the same technique to melt it away?
- SDSteven Dell
Not really. You can just f- fold it, pull it out, or cut-
- 2:36:48 – 2:39:05
Questions about corrective eye surgery
- PAPeter Attia
One other question I had on the laser surgery I forgot to ask was, um, uh, do you have, how stable does your prescription need to be? Um, because if I understood correctly, again, there's two things that are driving that, right? There's the length, which presumably that's the part that needs to be stable. You don't want the length to be changing.
- SDSteven Dell
That's right.
- PAPeter Attia
But the shape of the cornea you're actually fixing, so if there's anything that's changing there, do you care?
- SDSteven Dell
Well, there's really three variables if you think about it. There's the cornea, the retina, the, the length of the eye, I shouldn't say retina, but the length of the eye, and the lens itself.
- PAPeter Attia
The lens, yeah.
- SDSteven Dell
So we know that the lens is gonna continue to change throughout life, but typically not until you're in your 50s, 60s, 70s when cataract formation will start to affect the light bending power of, of the, of the lens. The cornea should not be changing. That would be a sign of-
- PAPeter Attia
So you just have to make sure this length is fixed.
- SDSteven Dell
That's right. And typically that, unless you're someone going back to law school or you're reading 30 hours a day, that is typically finished changing in the early 20s, like around 23, 24.
- PAPeter Attia
So does that mean our prescriptions shouldn't be worsening much as we age?
- SDSteven Dell
They really should not be worsening unless you're developing some cataract formation.
- PAPeter Attia
Okay. Yeah, I think mine have been stable for about 15 or 20 years, so that means I'd be safe to have laser eye surgery from the standpoint of stability of prescription.
- SDSteven Dell
From the standpoint of stability of the prescription, that's right. And then at some point in your future, and we tell patients this, at some point you're gonna start to develop some cataract formation, and hopefully the boxing won't have any effect on that, UV exposure, you, you know, won't have any effect on that. Genetics will be in your favor and, you know, but if you're a, uh, I didn't mention radiation is another, you know, we see people who do fluoroscopy, like f- health professionals-
- PAPeter Attia
Yeah. Yeah
- SDSteven Dell
... who are involved and exposed to ionizing radiation.
- PAPeter Attia
Oh, wow.
- SDSteven Dell
I mean, if you are the-
- PAPeter Attia
If you're the tech working the fluoro-
- SDSteven Dell
If you're the ship captain, uh, who smokes, uh, on a boat that's carrying nuclear waste and you're diabetic, you're gonna get cataracts, um-
- PAPeter Attia
A lot sooner
- SDSteven Dell
... a lot sooner,
- 2:39:05 – 2:49:17
How an eye exam can be a window into metabolic illness
- SDSteven Dell
yeah.
- PAPeter Attia
Yeah. So the last thing I want to talk about was, are we ever going to have a day when just as we look at hemoglobin A1C today, which is a pretty crude, unimpressive way to assess glycosylation.
- SDSteven Dell
Right.
- PAPeter Attia
Um, I've, I've ranted on this elsewhere, so I don't, I won't waste your time with my rant on why I think hemoglobin A1C is not especially helpful outside of extremes. But I, I, I don't know why. I just think the eye is the most sensitive end organ-
- SDSteven Dell
Mm-hmm
- PAPeter Attia
... to excessive, uh, glycosylated hemoglobin, and it's also one of the few things you can look directly at.
- SDSteven Dell
Yeah.
- PAPeter Attia
Um, so, you know, I know when I was in your office just for giggles, I wanted to have you do, like, basically an angio of my eyes noninvasively.
- SDSteven Dell
Noninvasively, yeah.
- PAPeter Attia
And, um, I thought that was really cool. I liked knowing that I had beautiful little vasculature back there.
- SDSteven Dell
Yeah. Your, your capillary network was the envy of everyone in the office. Really, really good. No, but what's, what's so cool-
- PAPeter Attia
Like what stands in-- I mean, is there going to be a day when everybody-
- SDSteven Dell
Yeah
- PAPeter Attia
... is doing this every year, and when we see changes there, we say, "You know what? I don't care what your... Your hemoglobin A1C might only be 5.5."
- SDSteven Dell
Right.
- PAPeter Attia
You're, quote, unquote, "normal."
- SDSteven Dell
Right.
- PAPeter Attia
But that might actually reflect higher turnover of RBCs, and in reality, there's a problem.
- SDSteven Dell
You know, so it-- one of the really interesting things about the eyeball is that it's a transparent organ, as you point out.
- PAPeter Attia
Yeah.
- SDSteven Dell
So you can just sort of look in and see what the problem is. It's not like, okay, there's belly pain, we need to do some testing. You can just sort of-
- PAPeter Attia
Yeah, it's not like the spleen, where you have to use more complicated tricks to look at it.
- SDSteven Dell
That's right. You can just look in and, and because, for example, we have a layer of brain tissue readily available for us to observe, including its capillary network. So we can look and see, are these capillaries damaged, which is something you see in diabetics. Are they exudating fluid? Are they leaking fluid? Uh, and that's a very early sign of, of diabetic retinopathy. Could you, for example, image the lens and determine is glucose leaching into this lens? Does it contain more glucose than you would expect a, a normal individual to have in their lens? Might that be a screening technique for, for diabetic disease? But I, I think probably yes. Um, and what about the fact that diabetes manifests primarily as a microvascular disease in so many end organs-
- PAPeter Attia
Mm-hmm
- SDSteven Dell
... and we can actually directly visualize this microvascular disease occurring. So if it's in the eye, it's probably in the kidney, it's probably in the toes, and those are things that we can directly observe.
- PAPeter Attia
And again, it's not binary, right? So it's not... You know, we, we, we, we make the diagnosis in a very binary fashion. When the hemoglobin-
- SDSteven Dell
Mm. Right
- PAPeter Attia
... A1C hits 6.5%, person has type 2 diabetes. But, you know, at 6%, we just say they're pre-diabetic, and at 5.6%, we say they're normal. But of course, if you understand everything we're talking about here, that couldn't be further from the truth. It's not like a person's going to be perfectly pristine and then they're going to be diabetic. This is a spectrum. And I, I just think that this, to me, is a much more interesting way to go about gaining kind of a foothold in our understanding of a person's metabolic health, is to sort of create this as now a new standard, right? Th-there's something I'm going to create as a standard for myself, right? Which is I want to make sure that these, you know, nearly invisible arteries and capillaries are perfect, and when they cease to be, it's going to prompt investigation, right? Whether it be lipids, whether it be glucose, whether it be any other thing that we can... You know, blood pressure, right? I mean, all of the things that can damage a microvascular system, this becomes a beautiful window in which we can look at them. What, what, what is the cost of doing that test? If a person said, "I just want to-"
- SDSteven Dell
Well, it's super... Yeah, it's super inexpensive to do, but 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. I think that the first-
- PAPeter Attia
And you, you measure that via pressure or shape as well?
Episode duration: 2:49:17
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Transcript of episode 1SavpBUUy2Q
