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

hey everyone welcome to the drive podcast i'm your host peter etia 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 right and everybody myself included is comically ignorant on this topic i i mentioned to you a few minutes ago the extent to 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 there you go you're ahead of the game i remember something called a fovea right 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 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 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 uh actually quite a lot obviously 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 there are a lot of crossovers to other medical disciplines all of the 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 there is a discipline of medical training or of visual training basically optometry yes which deals with the eye but not all of the the surgical stuff so we work in a collaborative fashion with optometrists and those are the folks who are fitting glasses they're screening for eye disease they're handling pre-operative and post-operative care in many cases they're treating some diseases that are specific to the eye like glaucoma for example and we work in a collaborative fashion with them and does everyone in an ophthalmology residency spend time operating there's no there's no non-surgical discipline to this right it doesn't bifurcate in the training 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 but there are for example neuro-ophthalmologists which are really more neurologists than eye surgeons in fact it's typical that they don't do eye surgery uh so there there are some ophthalmologists who don't do eye surgery you know one of my sort of lasting memories from residency was stealing suture from the ophthalmology or at hopkins because um i guess for people who don't know uh the number of the suture of course gets larger the suture gets smaller so an o suture is like you can see how thick it is it's like a piece of rope right 10203 by the time you're at 4-0 it's it's actually quite thin right we use 11-0 exactly and cardiac surgery you're using a 7-0 yeah 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 i mean just the slightest tug too much and it breaks but then in ophthalmology you guys were at 11-0 and so i used to steal 11-0 constantly every night i was on call and practice suturing with 11-0 right the thinking being if you can tie an 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 so i used it to help me develop a good feel for fine suture um yeah but and then i also realized i'm kind of being a schmuck here i bet this 11-0 stuff's really expensive and i'm just stealing it like there's taken to the call room all night more likely it was probably 10-0 but yes it's i mean our our tools are little tiny tools and i i can remember you know our operating room when i was in training was sort of near the orthopedic surgery exactly area and you hear this black and decker stuff going on over there and our little tiny tools are very it's just a totally different do you is everything you do under a microscope operationally like you don't operate with a naked eye right right yeah i mean there are right it's a it's all under a microscope either you know the just to put it in a visual for people who may not be familiar we have a binocular microscope so i'm looking through both eyes and this is either mounted from the ceiling and has controlled by my feet so 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 and so i'm sort of sitting i'm looking straight ahead but so the image is here but i'm operating down here and it's interesting because sometimes my wife will kid me i'll come home from a day of surgery exhausted but she said she says something like well i don't really get it you're just sitting in a chair sort of making these little tiny movements and there's soft music playing it all seems very very sedate it's incredibly stressful and exhausting although i will say in your wife's defense yeah she has it harder because of the kids yeah that's true for sure let there be no misunderstanding about that it's it's way easier well actually i didn't realize i never really thought about that but the other advantage you have is you don't have that cervical flexion problem that most surgeons have when they're in an open you know i mean nowadays with more robotic and laparoscopic surgery that's right you can be in an advantage neck position but we have a different problem though and that is that people tend to and i don't want to mess up the sound and microphone but they tend to hyper extend they had to send us to bring their head forward to come up to the oculars yeah yeah yeah and that creates a whole other set of problems so there are ergonomic challenges for sure and i remember early on in my career i was i was coached very carefully on how to sit how to have your spine arranged don't crane your neck forward and make sure that your shoulders are down it's interesting because when you train surgeons and you look at them they're all sort of raising their shoulders up and they're terrified that they're going to do something wrong so they're in a very very compromised and stressful position and then they tend to lift their hands up so they're actually and again i mentioned earlier that these are little tiny movements so very small positional changes can have a huge impact on the outcome of the surgery yeah i have a number of friends uh two in particular from residency who have had multiple neck surgeries uh including one that required such a significant extended fusion that he could no longer operate so he trained as a cardiac surgeon and now does cardiac critical care so still a great career but yeah you know after 10 years of training as a cardiac surgeon can't operate anymore yeah i mean surgery it takes a toll on the on the surgeon for sure um so when you went to medical school did you know you wanted to do ophthalmology not really i think i knew i wanted to do something surgical i wanted to do something with my hands i'd kind of always been good with my hands and i could draw reasonably well and and and you get as you kind of know you get feedback early on in your surgical in your medical career if you demonstrate that you're decent with your hands people say hey you're pretty good with your hands you should think about something surgical or maybe not they say have you thought about radiology or something along those lines and so i kind of knew that i wanted to be a surgeon um and but really didn't know what type and it was i remember a eureka moment where the first time i looked through what we refer to as a slit lamp which is basically like a microscope to look into the eye the very first time i looked through that instrument at an eyeball i was hooked i knew this was what i wanted to do and that was something you did during an ophthalmology rotation or were you doing an er rotation and somebody came in with something stuck in their eye it was during an ophthalmology rotation and i'd had some exposure to ophthalmology because a friend of mine's father was an ophthalmologist quite a famous one and i had a background in photography when i was a little kid so i kind of understood optics well but that was during one of those one week you know do a little ophthalmology do a little ear nose and throat do a little bit of whatever it is and that was that was the nice thing about medicine is you kind of get to taste a little bit of everything before you decide you're going down a particular pathway so um it's funny i didn't really overlap with ophthalmologists so you guys didn't do a general surgery internship i'm guessing right some of us do that i did what is referred to as a transitional residence uh internship where you do a little bit of everything you do general surgery internal medicine you you know you do a little bit of everything that's that's very helpful um and the the general surgery part i will confess that was rough i mean as as you well know um but it was nice to have exposure to a little bit of everything so um the that's probably a four-year residency i'm guessing when you include the internship that's right yeah and um back in the day when you did it how what was the bread and butter you always kind of judge a discipline by what the bread and butter is of the era right so general surgery if you did it in the 1960s and 1970s the bread and butter would have been bill roth procedures and things like that where you know the the most common thing you were doing was cutting out half of the stomach because of peptic ulcer disease and things like that by the time i got to residency like i never did one of those right because you know h2 blockers and ppis basically eliminated the need to surgically remove part of the stomach for gastric or peptic ulcers so um at the time you went through your training right what was kind of the where did 80 of the volume come from what type of cases yeah still cataracts cataract surgery and then retinal disease you know the scourge of essentially diabetes where you had these very very complex retinal problems so those were really the the two main ones so this is probably a good moment 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 cornea these are like i kind of know the retinas at the back of the eye that like it's just embarrassing right even how much of a luddite i am when it comes to this part of the body so um i can say this literally talk to me like i'm a four-year-old okay explain the eye to me that's good that'll work for both of us so you know it's funny it's funny you mentioned 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 what is this guy talking about a camera thing on your phone what is he talking about film what is that you know a 50 year old understands that 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 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 and 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 or light rays come in parallel and they're bent so that they fall perfectly on the retina and what does that mean fall perfectly on the retina meaning yeah they uh is there like if you think about the um back of the eye here right what fraction of the back of this sphere is considered retina all of it everything yeah all of it the whole back of the eye is coded 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 of the bullseye literally of the of the retina so when i'm looking at you images from you are falling on the phobia 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 problem and nearsighted again the way i used to remember this because this is literally how little i know nearsighted means you see things near well yes that's right and so those are people like me who need either glasses or contact lenses to see things at a distance correct so this is uh you know typical cocktail party banter or someone will say i think i'm nearsighted or maybe i'm i'm both nearsighted and farsighted um so nearsighted means you see better up close farsighted is a little trickier because far-sighted people see better at far but their far might also be kind of blurry it's just that the near vision is even worse so that person who says i'm neither i'm near and farsighted could be that's an accurate statement that's a plausible no it's actually probably that they're what we refer to as presbyopic which is that they see well far away but their focusing ability is compromised typically through age and they can't see up close and we'll get into i want to get to that in detail because i experienced that a few years ago in a manner that rocked my world because it didn't happen gradually yeah that seemed to happen overnight and so it yeah it's funny you say that 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 but the reason that comes into play is that when we are young when we're born the lens of our eye is extremely elastic it's like a gummy bear and it can change shape to bring near objects into focus but as we age and this is universal the elasticity of the lens goes down and we're no longer able to sort of zoom focus in and you have it have to start pushing things farther and farther away or get some sort of optical aid like a pair of spectacles to see up close that process continues as the lens becomes less elastic and harder eventually resulting in a cataract where it begins to begins to lose its optical clarity so now you have a lens that's stiff hard and starts to become opaque so that's kind of the so a cataract is a disease of the lens correct and it's a natural i guess this is kind of a gray area do we consider this to be 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 2 diabetes is a pathology not necessarily a normal consequence of aging that can be avoided yeah that's a that's a really good uh and interesting way to look at it so i think that cataract formation is a universal component of uh you know doe days on earth you know just the i i don'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 sort of surprising like being electrocuted can actually cause premature cataract formation but that's one sort of exotic weird one but trauma head trauma can certainly do it just head trauma not necessarily eye trauma you know the head i mean obviously they go hand in hand typically the 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 so right the point is it doesn't have to be direct trauma to the eye it's simply the the coup counter coup for example of the brain are presumably also being reverberated through the vitreous fluid that's exactly right so if you think about you know the eye as a fluid containing organ and when it receives trauma and just as you mentioned with coup and contra coup injuries of the brain inside the skull i think those same forces come to bear on the eye itself so i think it's more common when you do have direct eye trauma but i think even 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 so is the lens of vascular structure no it is not and the protein if you think about the lens it's kind of the shape and about the size of an m m candy just like a plain the chocolate ones yeah the chocolate ones right you know just the ones without the nuts or pretzels or whatever they're putting inside m ms now but the the you know a plain m m candy yep and it's got a coating kind of like the candy shell and the protein inside the chocolate is optically clear when you are a kid and that protein does not turn over or exchange but the membrane the can candy coating the so-called lens capsule can allow molecules to diffuse in and out so a classic example of this is someone will point out hey you know my vision my glasses prescription suddenly changed it i became much more nearsighted or i became much more farsighted in the space of a month and i i went to the eye doctor and they said wow your glasses are totally wrong and the first thing i think of is go get your blood sugar checked because glucose can diffuse into the lens cause it to swell and that will change the shape of the lens the lens becomes physically bigger so it's like a thicker more powerful lens so it's an osmotic chain correct basically and the the time frame for that to happen is over a period of several weeks so if the blood sugar goes up it may there may be a lag of a month or two before the vision changes and when the blood sugar goes down same thing it takes weeks for that to kind of go back to normal so is again i'm just so i'm almost struggling to organize my thinking around this but the other thing that comes to my mind when you think about an avascular structure is what is the immune what is the immune system's behavior around the eye are these immune privileged sites are they more or less susceptible to certain types of infections systemic infections that is obviously i know we'll probably talk a little bit about sort of local infections but yeah i mean 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 but 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 uh small molecules can and that's why it's going to be important from a pharmacotherapy standpoint it is it's and for example there is a technology there's a there's a medication that is a lipoic acid cholinester that is being examined as a way of softening the lens 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 so you're saying there might be a day when there's either a topical or injectable substrate that could go into the lens that could delay the onset of farsightedness and the onset of cataract that's the hope this is sort of at the moment it's a little bit of a pipe dream because it's in the early experimental phase but human trials have begun to look at the lens softening properties of this particular compound the trick is you've got to you've got to use it in a topical fashion so putting in an eye drop and that drop has to run the gauntlet of going through the cornea which has lipid layers and 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 and that's why it's that particular drug or compound is a choline ester because that allows it to get through that the lipid layer in the front through the aqueous through the water portion of the cornea and then hopefully into the lens itself uh and that's not easy to do so the lens is a relatively privileged area both from an immunological but also a pharmacological state so that that would help that that's what helps it also stay clean stay clear yeah you know it's gotta you want the lens to be optically clear let's go back to a little bit of the front of the eye so the pupil we all recognize is the dark part right and see you know we talk about the dilation and constriction of the pupil is the pupil itself actually changing in size or is it just that the iris is moving the colored part of the eye yeah is is it dilation means it's actually moving back and constriction means it's actually closing that's that is correct it's a the physical aperture changes in size it gets bigger it gets smaller so when they when you go to the eye doctor and they dilate your pupils they are physically opening up the pupil pharmacologically and that's mostly so we can see into the back of the eye and you do that by forcing the iris to move out of the way correct the iris has a it almost looks like the the like the the aperture of a of a camera yeah and so it you know you can either constrict it or you can 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 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 been you've expanded the depth of focus wait this is let me make sure i understand this you're saying that putting the lens aside for a moment which is a great source of the pathology the inability of the lens to move in and out and then call it the z-axis if we want 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 that's exactly right so imagine it's kind of like squinting yeah 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 now this is again is a little counter-intuitive to me because anybody who's in my shoes who's experiencing uh far-sightedness or i shouldn't say knows that nothing makes it worse than darkness correct and so you're in that rest 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 going to read their kids in bed when it's kind of dark it's beyond me like there should be a mandatory 24-point font for nighttime books for little kids but anyway he's got this one book and he even tells me before he wants that book ready he's like daddy go get your glasses right um and then the other place is the restaurant right where it's usually totally lit but in both of those situations isn't my aperture narrowed because oh no of course it's the opposite so if you put the sun on something you're going to be able to read it because you're a pupil so is that why light makes it different some of it is just the absolutely it's pupil effect alone and some of it is just the light there's much more light energy available for you 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 you can actually see so in the clinical trial that we performed to look at this um those competing forces were examined very closely and we found that the aperture effect the depth of focus outweighed any loss of velocity from from loss of light and how long would these um eye drops stay in effect how long would they be able to maintain after you put them in i think about it depends a little bit upon eye color believe it or not because uh something i want to ask about in a moment yeah you brought that up yeah a certain eye color like light eyes tend to react more to any given uh strength of dilating medic drop or or constricting um but about six to eight hours maybe up to 10 hours so this would be a once a day maybe a twice a day eye drop and would this have any impact would it compromise your far vision quite the contrary what was really interesting is that when we looked at patients who had their pupil size reduced pharmacologically their distance vision also gets better by the same principle because their depth of focus is so good so in the same way that you can squint and make out a highway sign if you're a little bit nearsighted or a little bit farsighted or have astigmatism which we haven't even talked about yet which i don't even know what that is even though i have one that's right and squinting makes that better by the same token the pharmacological manipulation of your pupil will do that as well and by the way i think you will see in early 2022 commercial availability of these of the first of these drugs so going back to the more complicated drug you were talking about that has it's complicated because it has to make its way into the lens that's right i can now see why that would be more about the cataract issue and not about the presbyopia issue because this would be a much easier way to solve presbyopia because you only have to basically get onto the iris yeah well you're looking at a drug that shrinks the pupil and works in 15 minutes versus something that softens the lens that might work in 15 months so i think it's they're very different markets and while that lipoic acid cholinester is being pursued as a presbyopia near vision aid or something to reduce the effects of i think their real goal is to reduce the incidence or delay the onset of cataract formation which would be really cool yeah 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 yeah it's a protection from uv light and from from visible light in the same way the different skin tones have emerged so typically you see dark-eyed people closer closer clustered closer to the equator because you know the 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 so the what's called the retinal pigment epithelium which is the pigmented layer behind the retina underneath the retina that is responsible from 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 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 so the other thing i do remember vaguely from medical school is rods and cones yeah and uh of course i also remember a few other things now that we're talking about it about you know where the um which part of the brain actually does the signal processing and stuff so let's go back to the light hitting and what are the rods and cones and how are they processing that signal 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 phobia 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 and is each rod and each cone what is it is it is each one a single cell yes that's right they're each highly specialized cells obviously they have mitochondria obviously they have is there what distinguishes them do they have photoreceptors like what makes them unique they are photo they refer to as photoreceptors and they have stacks of structures within them that are photosensitive and that causes a depolarization which so they work like channel opsins do they they use a photon to create an action potential 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 wow yeah okay so all of that ion flow ultimately makes its way to the optic nerve correct that's right and to the brain and most of the visual processing is in the very back of your brain so that's 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 now 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 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 how much of the visual processing is in that neocortex is it virtually all done there is any part of it done in the midbrain yeah stuff like pupil responses the autonomous those the autonomic stuff those are in the midbrain but the visual processing and the actual mapping of the visual sphere and even as hierarchical as parts of the brain that are specific to edge detection or moving edge detection or edges that move this way or that way that's all been mapped quite elegantly and it's in the cortex is there a cross yes is the left doing the right and vice versa that's right but remember you're you send information from your left visual sphere to the right side of the brain but you're getting information now there was this is the trick both eyes yeah so so both eyes yeah explain how that works because this i remember in med school needing to draw this a few times how long do you have it's you know the simplest way to think about something is that at the pituitary there is something called the optic chiasm you probably remember where the the optic nerve is right some of the fiber half about half the fibers cross so if a visual deficit is in one eye only we know that it is in front of the chiasm correct and if it's behind that it should affect both eyes maybe asymmetrically but it should affect both eyes and that could be very helpful in localizing where a particular problem is now a lot of that's done through imaging but it used to be there was quite an art to this clinical to this clinical exam which you know sadly we've lost a lot of yeah this is and i do remember both in neurology um and probably neuroanatomy kind of going into these really crazy tests that you'd see the patient performing the test and missing a certain thing and you'd think they must be faking it like there's no way you could produce such a bizarre deficit in this one part of this one visual field then of course you see and look there's a tumor and it totally explains this once you understand the the how the uh how the nerves cross 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 you know diagnose brain tumors we find things that are systemic diseases that have ocular manifestations so you're obviously well aware that your brother and i are close friends and he's become pretty obsessed with hunting now and uh i'll take full responsibility at least for that part did not see this one coming yeah well you'll see where this is going right so so he's become super obsessed with hunting and one of the things that hunting teaches you yeah um is how we stack up to wild animals right so if you're out hunting an elk or an axis deer or one of these remarkable creatures right especially with a bow and arrow yeah i was going to say how much technology do we have access to in this hypothetical scenario so no let's talk about yeah let's talk about bow and arrow hunting where you really i mean if you really want to reduce the margin of error you want to be inside of 50 yards to be able to take that shot sure 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 um but i generally think of the three big senses right which is the sense of vision the sense of smell the sense of hearing and there's simply no comparison in sense of smell we basically can't smell we're we're effectively useless creatures you know they can smell us with if they're downwind of us they can smell us a mile away literally one mile away if the wind moves from you to them they're gone you'll never get close to them right um it turns out that the closest sense we have to our prey is vision right 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 and birds yeah yeah um but for the most part like this is the one sense that we have right rivals the best right uh is that because we both had to as you said be hunters and be hunted for such a large part of our revolution is that i mean this is sort of teleologic explanation i'm looking for but 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 many many orders of magnitude of change of illumination like it's astonishing that you can function in both of those environments well that's actually interesting that you make that point because as it gets darker we do tend to have an advantage over some of the animals now it turns out to be very short-lived there's a very narrow window at dusk and dawn where i think we can outsee them and maybe that's the benefit we have in that we evolve slightly better to have this greater range if you will um but i've always been amazed at like why did we not develop a sense of smell i mean because we effectively can't smell compared to animals i mean it's really for sure absurd how different it is and i i don't know why evolution didn't push that harder and even our hearing i think is you know we're not even nothing compared to them yeah but vision you know and if you ask it's it's very common for patients to grab my arm as we're going into surgery and they'll say dr dell you don't understand my vision is really important to me i've got i i've got to see i've got to see it yeah and we i get that you know it's it's the one sense that if you asked people which sense they'd be most willing to give up it's the least it's the last one yeah and and in covid we saw many people at least transiently lose a sense of smell and a sense of taste and of course it's inconvenient but it's totally survivable yeah it's hard to function in the world as a blind person and you know it's a fear that many of us have so it's a sense that we value very highly and also evolutionarily it's valued highly just owing to the fact that so much of our brain has devoted division yeah this is a little bit off track but maybe good for a psa um i 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 right and we didn't think about it so i'd be out in the backyard chucking things around cutting wood right smashing sherlocks never a thought to put on safety goggles and now my kids who are both completely obsessed with cutting down trees and like just they're always they're very active outdoors i mean they just know like you're wearing your safety goggles if you do that stuff because i'm totally paranoid they're gonna you know have one of these tragic accidents um what do you see much of that stuff i mean do do we for sure and you you know you see a lot of eye injuries i think injuries are one of the main causes of devastating visual loss in young people you know if you take visual loss in general almost all of the big causes and movers of visual loss are senescence related they're age related but in terms of vision loss in young people it's it's a lot of trauma what are the most common traumas that you see you know i think like is it unrestrained flying into eye or is it more i think it's more blunt trauma frankly wow yeah more blood trying the eye is pretty well protected with the brow and the cheek but you know there are certain things that can get in there and can directly impact the eye and so i think you know in a young person trauma is something you have to certainly watch out for 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 he's like why and i said because you're hitting sharp objects yeah the sharp object if one of them flies up and hits your eye he goes i would see it and i would close my eyes no you wouldn't yeah let's just put it this way those objects are flying at supersonic speed and they you can't blink that fast so do we have a sense of like what our reaction time is to blink that is known but i've long since forgotten what that is because you get the sense like if somebody's throwing you a ball that's right and you misjudge it you're gonna blink like that's slow and for sure that you can catch it but yeah but then there's other objects where you can interestingly you know i've operated on a number of major league baseball players and for them seeing the laces on the ball as hitters is enormous as their career 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 2020 before they had surgery but they wanted to be 2015 or 2010 and what that means is you know again here's another nomenclature issue what is 20 20 vision 2020 simply means that you can see at 20 feet what a quote-unquote normal person can see it 20 feet if you're 2010 you can see at 20 feet what a normal person has to get 10 feet up to in order to see so 2010 is better than 2020. so some of these guys want to be 2010 or 20 you know whatever it is 2015. we've been able to achieve that with modern forms of laser vision correction because wait a minute how is the isn't this now getting into the performance enhancing side of things isn't this kind of amazing you know it's interesting 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 he just said it'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 and there are ways to boost human performance beyond 2020. 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 does that vary from person to person it has to but it's somewhere in the vicinity of about 2008 or or so and so if you can have a sharp enough image you could theoretically see better than 2010 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 so why would it be beneficial i guess we'll talk about laser surgery and maybe you'll want to park this question until then yeah 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 yeah so 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 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 has 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 can achieve with spectacles or laser vision correction so particularly soft contact lenses do a very very good job but they don't give you super human vision performance typically you know it's funny i experimented two years ago with a stronger prescription than normal right to get me to 2015 in my dominant eye for archery sure um goofed up your near though that's the problem i just abandoned it immediately after like six months of suffering because it made my presbyopia right worse yes it just isn't worth it yeah that's right yeah that's the that's the challenge when you if when you pull the image farther and farther away uh you you're doing the same thing with the near image as well so let's now talk about how to correct these oh i guess let's define an astigmatism since that is yet yeah i mean it's it's when the eye is shaped like a football instead of a basketball and when you say the eye which part of the eye specifically the cornea the very front part of the eye typically how thick is the cornea by the way it's about as thick as a credit card like 500 microns yeah yeah like 550 microns something like that so half a millimeter yeah exactly right 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 you probably don't remember which one i have do you i do which one do i have you have corneal astigmatism that's the so that's the normal one yeah it's very pedestrian you're very boring patient but the uh the so meaning just to be clear yeah i'm not perfectly shaped i'm a bit oblong that's right shaped like an egg or a a football an american football right so um it's if you're walking along the laces of the football you would encounter a fairly gradual curve but if you took a right turn and walked in particular it would be very steep okay and so that means that the power differs by meridian yep so uh you need a different glasses prescription in this meridian versus this meridian and what's the prevalence of this it's very high i think you know 60 some odd percent of patients with glasses prescription have some significant degree of astigmatism why has poor vision or i was going to say why has poor vision been allowed to evolve i was going to offer that maybe really poor vision hasn't right vision that would impair your ability to survive through reproductive age probably didn't evolve maybe maybe there was a day when the genetic variability of eyes was broad enough that a subset of people were had really poor vision the type of people today who maybe we don't encounter right this is a super interesting topic and it shows you how plastic the evolutionary or the actually the adaptive component of the eyeball is itself so the length of the eye is really what determines whether you are nearsighted or farsighted when you say length you mean distance from front to back okay 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 let me make sure i understand that okay very long ap access you're gonna have a real hard time seeing things far away correct and is that because the further something is the harder you have a time focusing all that light well let's talk about the genesis of this okay 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 over what time scale 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 so if you could do an awful experiment it's been done 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 yeah and you would put that kid into glasses as a child 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 percent 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 so this really transcends evolution because you can change if you can change something in years within the it's not evolutionary it's just within the eye it's adaptive within the eyeball itself so if you take a group of children and this has been done seven to 11 year old children and you send half of them outside for 80 minutes during the school day for recess and half of them stay inside in an indoor environment for their recess the risk of or the incidence of nearsightedness is 50 higher higher or it's half in the group that went outside so you cut your risk in half by going outside now we think that without any instruction to go and look at things far away but just by the very fact that if you're outside there's so much more to see and you're going to be looking further out right and it and this has been further studied in terms of is it just being outside or is it the light yeah it's actually both but the light is really the most important driver of protection from nearsightedness so if you are outside on a bright sunny day you're releasing a fair bit of dopamine from your retina and dopamine inhibits the growth of the eye so the worst thing you could do is stay inside in a dimly lit room and perform near tasks that raises your risk of nearsightedness 16-fold compared to kids who go outside i'm sure there's epidemiology that would suggest that the further you are from the equator does that imply that you have a greater risk of near-sightedness just based on the light part of this argument yes there is some data to look at that 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 8am where there was less illumination and we know from animal models that it is illumination that is critical in this dopamine release so you know does that mean we need more skylights in classrooms or more windows we need more natural light could we artificially mimic some of the sunlight by making these rooms brighter and predict and prevent some of this myopia epidemic is a photon a photon a photon i mean does it i mean i i don't think that it's known frankly peter whether that's the case because there are different there's a whole spectrum of light so is the blue light more important this is tangential and we'll talk about this i know but blue light you hear all this negativity about blue light blue light is critical for wakefulness or intention for i think for preventing myopia and by the way when we say myopia nearsightedness it's not just the inconvenience of wearing glasses or contact lenses or having laser vision correction when you're 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 so it's not just the inconvenience of spectacles these are disease-associated conditions so going back to my evolutionary question it's quite possible that over hundreds of millions of years any deficit in vision that would have prevented you from reproducing or in or impaired your ability to escape prey would have taken that out so from a genetic standpoint right our vision should be very good and in non-literate societies it typically was so if you look at hunter-gatherer tribes there is no nearsightedness there are no uh you know kalahari bushmen with spectacles it just doesn't happen this is amazing this suggests that because my parents wore glasses i should wear glasses is not true well there is or is there an epigenetic part of this world both there is a genetic component and if you look at siblings of individuals who uh wear spectacles there there is a higher incidence of of myopia or hyperopia but that could be susceptibility right it could be susceptibility and the environmental trigger is what's going to do it in anyone and we don't know whether parents of reading children were reading children themselves so you know it's hard to separate out the the genetic component but there does seem to be a genetic component as well but the environmental component seems to be way stronger and more powerful so if you take parents who don't wear spectacles and you 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 it near for hours on end odds are they're much more at risk for developing nearsightedness so when i just think about this soothing lens of my kids so so my wife has perfect vision i don't um what is my diopter i think i'm minus three and minus four it's about right yeah so what does that mean in terms of the 20 scale i'm 20. you're probably like you know it depends on how much you squint and look at the eye chart we honestly don't really attach a lot of significance to the 20 100 or 20 80 whatever it is you're probably in that ballpark 2100 maybe but i'm clearly at the point where without contact i can't drive i can't do anything right i mean i can get i'm not as bad i know some people who you know are minus 15 yeah they literally can't they have to put glasses near the bedside that's right i'll spend the first hour of the day without contact that's right because you could probably you know things are very easier for me to read without my content very things for you are very well in focus at a typical normal reading distance so your eyes have been tuned like post-natally for near work that's in your development you must have spent a lot of time reading or doing near tasks that's the thing i was thinking about it's like i grew up in canada so from a light perspective it wasn't so great right two months of no light whatsoever um but i mean i didn't watch tv much as a kid maybe 30 minutes a day right i was mostly outdoors um so i don't know how much of it but i also didn't 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 for sure so the classic example is we see law students um who have great vision when they enter law school and then they read for 12 hours a day and then they come in and they say you know i think my vision's going yeah and and you look at them and sure enough they've become nearsighted and that's not rare in in many graduate school situations where there's just just you know grinding reading for hours on end so when i think about our kids because now i just think well what can i it's too late for me right but but so get them outside so they are so fortunately they live outside yeah but when they're inside they're obsessed with like playing with legos and trains and trucks and you know i mean that's near right so is it that hey that's there's nothing wrong with that but you just have to make sure they're spending a couple hours outside a day i think the data would suggest that good illumination would be helpful uh as opposed to poor illumination okay but you know you don't want to discourage near activities because those are really important developments that was the flip true so you mentioned that hunter-gatherers or illiterate societies who are out by definition outside all the time right there's no such thing as nearsightedness in them do they develop farsightedness not really i think that they are fairly well tuned if we want to use that term to distance vision to pray hunting and things like that so distance vision is is very well 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 on to the next generation you can go ahead and get cataracts because you're you're you're done you know genetically useful your utility so the cataract is sort of like atherosclerosis 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 it seems to be fairly inevitable 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. maybe their visual needs are significantly reduced at that age but if you took an 80 year old lens and you'd put it in a 20 year old person they would be shocked at how poor their vision is that's really interesting now earlier you mentioned that we think that senescence cells or at least the soluble secretory products of senescent cells are probably playing a role in this well i think in the lens it's mostly that the lens proteins are degrading or becoming 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 going into the lens 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 the trauma ones got me worried because i boxed for so long i took out 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 let's just put it this way the cataract would be the easiest thing to fix yeah yeah yeah you know that's you know cataract surgery today is like a four or five minute procedure and it's astonishingly effective how often does one need to repeat that surgery cataract surgery typically is not repeated it's a once-in-a-lifetime deal so you and what you're noticing is like you're wearing glasses that are dirty is that effectively what the patient with cataract is experiencing i think the first thing they notice is probably changes in their night vision glare halos streaks around streaks off of lights at night problems with contrast sensitivity for those who can appreciate that loss of contrast those are really early signs of cataract formation so then the patient comes to you they're 74 years old or let's say it's sooner they're they're 70 years old more like you're 64 or 54 yeah okay and you're telling them hey billy you've got cataracts right we're going to just ride this out until you tell me you've had enough typically we let the patient decide when it's the right time for them to have the surgery once we determine 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 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 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 practice would have been cataract surgery that didn't involve intraocular lenses no it did it did and there's a there's a fascinating history about the the evolution of intraocular lenses 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 sorry i need to take a step back because i'm actually kind of confused right does all cataract surgery involve the placement of an extra lens yes that's that's correct we all you know i'm there are exceptions to nitpickers who will listen to this but virtually every cataract surgery that we perform involves the removal of the cr the the cataract and replacing it with an artificial lens does that mean again you have to pardon my ignorance does that mean removing the entire lens or removing a diseased part of the lens that has remember our analogy of the m m candy yes so we leave we leave the shell right we open a hole in the front of the shell yes we take out all the chocolate and then we now we have kind of like a flattened bowl looks like a japanese tea pot yes flattened and we put the implant lens in that bowl and that holds the implant in place and is it a viscous fluid that gets hardened or is it a hard object that goes directly in it's actually a bendable plastic object and the bendability of it is what allows it to get in allows us to fold it up and put it through a tiny incision and then it opens up so that was a very big advancement when did that happen 1980s was when that began to because what happened before this so this is a really amazing series of stories but i'll abbreviate them in the interests of of of time but in the old days you know like ancient in in the ancient world if you 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 you now had a clear optical pathway again to let light in and this took someone who was functionally blind and allowed them to see shapes so that was better than right because you don't have a lens so there's no way you can focus all you can see are shapes but it's basically like taking someone who has no light transmission right and saying we're gonna let unfocused light go through right so you know some lights better than no light so that's what happened in you know hammurabi time so amazing that they under i'm always amazing for sure we look at that now and we say that's barbaric yeah the fact that they knew enough to do that is kind of amazing they probably tried everything else first you know and that way they probably dissected catavaric lenses and tried to figure this out yeah but and there are there have been artifacts uncovered that i think a lot of them were made out of gold but they would take a gold needle and poke it through the cornea and then it was called couching the procedure 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 and you see some of these artifacts from egypt this was done in in china it was certainly done in ancient greece there are that was how you dealt with cataracts back then by the way it's just worth pausing for a moment to reflect like so we're if you're talking about the pharaohs you're talking about what 5 000 years ago right this is not in an evolutionary time scale that's a that's a pittance my profession is an old one and and you think like it would be better to be the poorest person on earth today than to be the pharaoh of egypt five thousand years i think in in many ways you know or certainly it would be better to be in the bottom 10 percentile economically today than the top 10 percentile 5000 years ago if the best you have to your cataracts is some guy sticking a hot poker in your eyes that's right so then you fast forward to right after world war ii and there's an ophthalmologist in the uk named harold ridley and he notices that some of the raf fighters would have fragments of their uh canopy their plexiglas canopy shatter when they were fired upon and these things would actually get inside the eyeballs shards of of plexiglas essentially would be inside the eyeball and the dilemma was well what do we do with this and he learned very early on that these fragments were biologically inert that the eye was perfectly happy and people could walk around the rest of their lives with plexiglass inside their eyeball and that's a shard of sharp plexiglas so and this is one of those this is in part because the lens is so immune privileged this is well 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 but there was something about sharp plexiglas that but something about plexiglas so the light bulb goes off that wait you can put plexiglas which is essentially poly methyl methacrylate you can put that in the eye and the body doesn't really care that it's there doesn't mount an immune response so in the in ridley's book which i've read it's really amazing but some intern asked him well when you take this cataract out are you going to replace it with a new lens and he looked at this young intern in a very british fashion i'm assuming just said you know that'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 and then they uh they lathed a lens from a from some spectacle maker that was about the size and shape of the human lens and they actually threw eight of these in patients and it's there's a there's amazing footage of of i think one of the first operations they dropped the lens on the floor of course it's the only one they had so they pick it up and uh rinse it off and they they it's fine they put it in and these patients did like shockingly well and this was viewed as heresy and there was you know 20 years of you're blinding people and but eventually the technology went out it became um so there were bad outcomes presumably i think in the early days for sure there must have been for sure and there were but like any new technology the first iteration of it is probably terrible and maybe just a little bit less terrible than the alternative and now it's it's it's a ubiquitously used so i never though because basically i didn't realize until you said it that polymethyl methacrylate is all over the body in terms of joints like and you do a you know when you replace a knee joint right that the tibial plateau i think is made out of polymethyl methacrylate so presumably there's something about it that is just well so visible to the immune system well we don't and we don't use that material anymore because it's stiff it is not deformable right so you had to you had to in the old days you had to make a fairly large incision to get the get this thing in first of all to get the cataract out and then to get the implant lens in two converging technologies made that go away the number one was we were able to take the cataract out through a tiny incision because you break it into we break it up we emulsify it essentially with ultrasound and now we even sometimes use a femtosecond laser to break up parts of it but the bottom line is that we can remove the cataract through about a two something millimeter incision which is very small like the thickness of a pencil lead basically and we can now take these implant lenses and fold them up and put them through that same tiny incision and then they can open up and be exactly where you want them to be now why is it important for the incision to be small well if you make a big incision obviously it takes longer to heal but it induces astigmatism so you want the incision to be tiny so does the um using your m m analogy does the coding on the surface of the m m grow back no it does not so it's it's fixed whatever hole you put in there they're stuck with yeah it's fixed now sometimes the coating the m m candy shell can begin to opacify after surgery and we can treat that in the office with a laser where we can just disrupt that that coating so this has got to be like my mom actually 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 yeah right my dad has he's 83. um i'm trying to think he must have had surgery then by now right now yeah odds are so i i i can't believe i've never really talked about this with him but is it it must be a game changer for a patient to come out of the the clinic or the or whenever that wherever these pro is this and do you do this in your well you have an or in your office we do but cataract surgery we do in an ambulatory surgery center but you know it may be that your dad didn't talk about it because it was such a non-event you know you go in for cataract surgery and the next day you're kind of back to your regular right but wouldn't it have been a big event in terms of his ability to see for sure especially now that the implant lenses can correct the near vision and the distance vision so that in addition to the added clarity from just removing the cataract they patients typically have this benefit of not needing so this is a procedure we should all be looking forward to when it comes like you're gonna know if i would go that far i mean it's still surgery there are risks associated what are the biggest risks you know i think that the number one thing we think about is infection but it's extraordinarily unusual to see an infection less less than one in ten thousand cases okay where you'll see a serious infection it's like any other surgery in the body you look for bleeding damage to the inside of the eye you have to keep tabs on the pressure it's basically everything that you would look for if you were taking out an appendix you're also dealing with in the eye what fraction of patients do not have a material improvement in their vision or have some deterioration of even another subset of vision so yes you've taken away my cataract i now i have i can see better in the sense of clarity but oh my god i became abjectly nearsighted as a result of it yeah i think that's that's pretty unusual because the science behind getting the prescription correct or very close to correct is pretty advanced and tell me what that entails so if i came in and right now i had a cataract right what are you assessing microscopically to make it so it's i'm getting the impression not everybody gets the same lens 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 money gets you what i mean i think the more money people pay the more spectacle independence they get in terms of optical quality all the lenses are how much does a lens cost a pair i guess since you're doing both i mean i i'm the wrong person to ask honestly i don't even know but directionally like if somebody has to pay out of pocket for one of these if they're getting just like regular cataract surgery and there is no attempt to get rid of spectacles it's probably going to be completely covered by their health insurance and if they're saying i want to go premium all the way get rid of it could be thousands of dollars out of pocket if they want to get rid of all their spectacle and dependents 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 this is this is amazing 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 right 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 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 want to see well and that's easy to achieve as well but as these lenses have gotten better our capabilities have gotten better if i needed cataract surgery today right knowing my diopter the minus four minus three business with the slight astigmatism although i still haven't figured out how that's impacting my vision right 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 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 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 going to see like a perfect 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 can you tune it like for example if i said you know stephen look i don't care if i have to keep wearing contacts right i would love to not have to wear reading glasses right because if i'm going to be honest with you the reading glasses are a way bigger pain in my butt than contacts because i just put my contacts in in the morning and take them out at night right it really doesn't faze me yeah reading glasses annoy the hell out of me because i never remember to bring them to restaurants ever so i'm shining a phone light at my menu and putting it out here and or i'll be reading the book to my kid at night and i'm like oh hang on buddy i got to go get my glasses like that's actually more of an imposition of my life yeah it's not an unusual request where we can intentionally set your vision for near or leave it for near you can certainly do that it's just an optical calculation to set the the point of focus where you want it to be you asked earlier about well what happens if i come into the clinic what gets measured yeah well one of the first things that we have to do is make sure that the surface of the cornea is tuned up from a dry eye standpoint because that those dry eye you know patients they're the surface of their corneas it's not optically pristine it's a little distorted the contact lenses make that better or worse it makes it a lot worse and it can throw off our measurements which can throw off our calculations because it's kind of pretty simple newtonian physics right if you know the length of the eyeball and you know the curvature of the front of the eye and you know the index of refraction of the stuff that's inside the eyeball how bendy this the material is light bendy the material is you can correct for as long as you know where the implant lens is going to reside you can correct for placing that image on the retina so the more perfect the shape of the cornea right the better that calculator that's right and that is probably the weak link in the measurement uh in the set of measurements that we take because we can measure the length of the eye we can measure the length of the eye from front to back very accurately with lasers so we can sort of it's almost like a sonar but with light we can bounce a beam off of the back of the retina and we know exactly how long the ret how long the eyeball is and we know roughly where the implant lens is going to rest when we put it in and if we know some other dimensions of the eye and use the front curvature as one of our pieces of data we can predict what power implant lens to put in wow okay so is there anything left on the uh iol front or has that like is there another huge step function of technology that's going to be coming there because it doesn't i it already sounds pretty remarkable well i you know i'd in the mid 2000s i started getting involved in product design for a type of implant lens that could actually zoom focus um front to back not a bifocal or a trifocal where you had different zones of focus but a lens that could actually move or change its shape and i developed an implant that we put in humans in multiple clinical trials outside the united states and we found that we could zoom focus kind of like the human lens would but the multifocals which are the lenses we've been talking about like bifocals trifocal implants surpassed the capability of what we could achieve with the lenses that i designed and 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 [Music] 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 from near to far that would be a game changer and um i assume that there's no you don't take like the lens from a young person who's passed away and ever try to implant that into no it doesn't work the way a cornea does that's right that's right in fact if you violate that capsule of the lens the lens immediately becomes cloudy so here's an example let's say that you talked about trauma so a typical scenario is uh somebody is uh working with a weed eater or whatever a weed whacker yeah and and a piece of 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 you violated the privileged site it's no longer privileged and within days you start to see a cataract and they need a new lens they need a new lens for sure do they need a new cornea by the way well they sometimes do 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 wow so um let's talk a little bit about corneal pathology so everyone's probably heard about corneal abrasions uh it's a very important reason i remember it's one of the few things i remember right in surgery you always tape the patient's eyes shut right because you know you don't want an eyelid flipping open in the middle of surgery and nobody's paying attention and the drape is running over the eye that's right scraping the cornea um is that the biggest insult that we think about for the cornea i mean that's probably one of the more common ones if you think about that eye that's being 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 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 being continuously bathed in in tears that they would be severely damaged so dry eye is intimately related to corneal abrasion because you lack the lubrication that normally takes place to prevent that type of thing and how much of a of an issue is that in our society yeah oh it's enormous it's uh i mean it's if you think about the things that cause dry eye um i mean there's obviously lots of medications that do it through cholinergic side effects absolutely but think about all the antihistamines you know hormonal influences are profound in terms of dry eye anything that causes dry mouth can also cause dry eye in that sense autoimmune conditions can cause dry eye so sjogren's rheumatoid arthritis all of the connective tissue diseases have a dry eye component to them perturbations of thyroid metabolism cause dry eye but you know a lot of women suffer from dry eye because they're i think it's mostly the influence of 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 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 i think it's the lack of testosterone why do you think that i think it has to do with the health of the epithelial cells on the conjunctiva 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 so what type of eye drops should we be using how do we apply them well it really depends on the type of dry eye that you have believe it or not because there are um you we think of tears as just salt water but that's really not what it is it's really an emulsion of lipids and mucin and all sorts of immune modulators and 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 salt water but the sebaceous glands that are in the eyelids we call them meibomian glands at the little where the lashes come out of the skin 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 all sorts of things that cause meibomian gland dysfunction some of that relates to diet and some people believe that a a diet high in saturated fats is more likely to cause meibomian gland dysfunction certainly colder weather like all like uh the secretions like the meibomian the sebaceous glands in your skin respond better to sunlight to heat 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 lacrimal gland shuts down even more so their dry eye is really multi-uh has it's it it's got uh a number of different causes now when i think about eye drops i i think about sort of the dropper that you try to get in your eye and you never get it at least i can never get it in my eye because i end up blinking all the time so then i you try and drop it into your into the corner yeah the corner and then let it but then i've also seen like the mist right yeah so so tell me about the different ways that one even applies yeah i think those are really the main ones i mean eye drops work pretty well for most people and but there are some mist sprays that believe it or not you can spray some of these there's one hypochlorous acid compound that you spray on the lids and it sort of migrates into the eye and 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 but most you know most artificial tears come in the form of an eye drop and that's okay so that's fine and it's okay if you can't manage to keep your eye open or should you force it and hold your eye open i mean it's you you gotta at some point you gotta get it in the eyeball yeah but that's one of just a whole bunch of strategies that we use for treating dry eye we add artificial tears but we think that there's a very significant benefit from supplementing with them omega-3 fatty acids especially high doses of omega-3 fatty acids and omega-6 certain types of omegas yeah which omega-6 is it again that's what you'd find in black currant seed oil or borage oil or evening primrose oil those are that's the gla yes gamma linoleic acid so that that is very helpful in in dry eye and interestingly you know there was a there was a very large randomized clinical trial looking at omega-3 supplementation in pretty high doses do you remember how high uh three grams wow of actual epa nda correct yes and the placebo arm was olive oil which is presumed not to have a benefit in dry eye and the it showed no superiority of omega-3 compared to olive oil however you know there's been a lot of criticism of this study it's called the dream study it was put on by the national eye institute it turns out that if you bring people into the eye doctor four times a year everybody gets better you know their compliance with artificial tears gets better and were they using artificial tears they were they were able to use whatever they would normally use to treat their dry eye so i i guess like in the same way that if you go to the dentist four times a year all of a sudden your flossing before you go to the dentist both arms of the study got better but it's our it is our very strong clinical impression that omega-3s in high doses help with dry eye primarily from a i think an anti-inflammatory standpoint let's go back to light for a minute yeah 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'm i'm kind of there's a part of me that thinks light is wow it's got to be really important i i think about you know all the time i get outside in the light it's great it's great but i also like wearing sunglasses because there's a part of me that's sort of afraid that too much uv light is damaging so what's the balance of of sunglasses versus not and i want to talk about polarized glasses are they right do they matter and all that kind of stuff 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 let's start with just the most obvious one the most common site of skin cancer the lower lid lots of basal cells squamous cell carcinomas sunglasses certainly reduce the incidence of that 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 and then the retina macular degeneration i think there's pretty clear evidence that uv exposure particularly of the magnitude that you can get outside is associated with an elevated risk of age-related macular degeneration now do we see this in hunter-gatherers who have otherwise amazing habits and therefore tend to be relatively privileged from uh optical pathology so the confounding variable there is that northern european ancestry is a risk factor for macular degeneration probably because of the lack of pigment because that pigment is protecting that very vulnerable vascularized component of the back of the eye oh wait so the darker your eye the more protected you are absolutely in the same way that your skin is more protected and more melanin so light eyed patients have more light getting in from the front of the eye and so their iris literally blocks less light hitting the lens yes and there the retina has less pigment behind it 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 but if you live near the equator or your ancestry is from that area then you're going to have more pigment and from an evolutionary standpoint but 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 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 so for example like let's so you you came over here today where it's middle of the day in austin it's a typical austin beautiful sunny day you're driving with sunglasses oh for sure absolutely 100 okay so you you're in sunglasses when you're outside i am after what time in the morning if i'm outside and the and my vision is better with sunglasses it's not worse with sunglasses than i'm gonna wear sunglasses i don't wear them at night and i don't wear them you know if it's very early in the morning but if if if conditions allow i'm going to wear them you know we talk about with um uh sunscreen right the importance of you know you're still susceptible to to sunburn in the clouds right if you're at the beach all day and it's kind of an overcast day you can still yeah do you do you recommend people still wear sunglasses even if it's not a clear clear blue day for sure and sometimes you know this kind of came up during the recent eclipse because you know people were saying okay i'll look at the eclipse this one was a few years ago i'll just use sunglasses well that's actually much much much much worse because you're increasing the aperture of your pupil because everything is dim but you're letting through all this very damaging light because no amount of sunglasses could block a straight shot looking at the sun correct so i think even on a cloudy day i do recommend that people wear sunglasses yeah okay what are polarized glasses doing you know as you know you know polarized lenses are essentially it's it's a lens that has a bunch of lines drawn in it all in the same direction so that some of the light is blocked but in one meridian all the light effectively is let through but perpendicular to that none of the light gets through and polarized lenses have some pluses and minuses one of the big minuses i found is that a lot of the displays in your cars now yeah you get this really messed up cross polarized effect where the light coming off of the screen is polarized and if you look at it through polarized glasses if you tilt your head it gets brighter you can not see it and by the same token many of the windows or winds i don't know if it's the windshield or the side windows but i've noticed wearing polarized lenses which i only wear for fly fishing now that i would get these very weird effects by tilting my head because of the cross-polarized effect essentially you have two different polarized filters and it's letting through variable amounts of light bending depending upon the orientation of your head and your eye and the spectacles i i've found myself more more comfortable in non-polarized lenses unless i'm on water yeah i think and then the issue there is that the light bouncing off the water or theoretically a highway it's all pretty much a lot of it is polarized in one direction that's the rationale behind polarized lenses and for seeing a fish if you're a fly fisherman for sure that's helpful i fly fish for the first time last month and i could see getting into that that is an art for sure it is but in terms of uh polarization there's no evidence that i've seen that polarization versus non-polarization in sunglasses helps it's really the uv filter that that is helpful for what we're doing in terms of protection of eye health you could wear clear spectacles as long as they had uv protection and still achieve the benefit of uh sunglasses yeah that's an important point right yeah the it's not the tint it's not the tin it's the ultraviolet protection and it's the same as true in a car right i mean the glass of the car is assuming you don't have tinted windows is still getting rid of most of the uv most of the uv but not all so you will see and dermatologists tell us this that in truck drivers who are in north america they 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 so you know even even you know car and truck windows let some uv light in okay so let's now go back to the standard situation of near-sightedness so a person comes in they're near-sighted right um decision one is i'm going to correct this with glasses versus contacts we'll start to talk about corrective surgery in a moment yeah um do you nudge people one way or the other i mean i wore glasses for the first four years that i needed 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 right because the call you know you're you're just you just couldn't be predictable about when you're going to put them in so i did all of residency in glasses and then since that time i've been 100 contacts yeah it's funny because well 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 internship started four months ago you know you know that sort of thing it was uh and so as you know residents are notoriously bad about their own uh health hygiene and and because you're so busy but uh and to answer your question more directly i don't really see patients for regular eye exams myself but so the people who see me are seeking surgery 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 wait do you use glasses and spectacles interchangeably yes when i say spectacles i thought so yeah referring to glasses to distinguish them from stuff you drink water out of so so yeah spectacles is our is the term of art for uh for glasses yeah um yeah so if you uh yeah you were thinking of some sort of exotic type of yes i was like oh there must be some mountain spectacular then there's a space it's like right down at ye olde spectacle something like that anytime my wife talks about pushing the gas pedal i'm like throttle it's a throttle application we need some gas now we need petrol okay right it's gasoline yeah or petrol it's not gas refers to natural gas when you push that thing it's throttle application yes okay yeah we're hard to live with aren't we yes okay so uh spectacles and glasses are synonymous okay um that's the safest thing you can do it's you you're 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 you might be susceptible to infection or is it laser vision correction but i tend to say if you're doing fine with spectacles or contact lenses do that i was kind of hoping you were going to tell me get laser eye surgery because there's a part of me that just wants to do it for the sake of doing it and getting rid of contacts once and for all but you were very much in the camp of you asked me a bunch of questions and at the end your 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 right they don't seem to bug you right and you like your near vision yeah yeah and so if you were to correct your distance vision with laser vision correction and set both of your eyes for a distance you would lose that near vision until maybe i get my cataracts fixed that's right then we can tweak it that's a whole other it's a whole other story right so let's talk about the advent of laser eye surgery so i think everybody listening to this has heard of lasik yes most people probably haven't heard of prk right um which we'll talk about when did pk came along first yeah a little bit earlier yes and that was when in the 90s right so the the approvals for prk and lasik were in the mid 90s 1995 1996 the first procedures were actually done in the first procedure was prk and it was done in new orleans and i happened to be uh in training there in new orleans and this was performed by a physician called marguerite mcdonald and she did the very first treatment on a human eye the way this came about was that eczema lasers which are the kind of lasers we use in lasik and in prk which stands for photorefractive keratectomy eczema 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 tissue could be etched or uh or cut and because it generated no heat there was no immune response generated typically 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 so the first eyes were treated in 89 and then that led to fda approval uh in 95. and the treatment in 89 was part of clinical trials i missed for sure it was part of the club so let's explain what prk does right before lasik 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 then again the cornea is about two millimeters thick now the coin's got a half a millimeter thick 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 by the way the length of the eye is the one that we talked about being somewhat malleable that's right development that's right and is the corneal shape hereditary is that the hereditary component of vision 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 so since we can't change the length of the eye what we can change is the curvature of the front of the eye and if you think about it you don't have to change the curvature that much think about how thin a contact lens is how thin is it i mean i know i can feel it but i don't know what that is is that also about half a mil no it's less i it's uh i honestly don't know i don't work in that world but it's pretty thin i mean it's like a little piece of cellophane if you think about like an acuvue disposal yeah it probably just feels thicker because of all the goo on it yeah it's so i don't i'm sure someone will correct me and say you should know how thick a contact lens is i don't but it's thin right it's pretty thin yeah so it's just that little curvature that needs to change in order to uh focus the light on the right and just to use an extreme example so you take somebody who has a very minimal degree of nearsightedness so let's say their diopter is minus one right then you contrast the lens that they would wear right to the lens that's someone who's near blind at like a minus 10. right what's the is the is the minus one creating more of a bend or less of a bend meaning is it a bigger curve or a smaller curve so the person who's minus one their cornea is less potent in bending light than the minus 10 person is that -10 means their eye is 10 units too strong and we need to uh to reduce the power of the eye so how would you fix that with a laser well well first of all how do you fix that with the contact so their lens has to look the curvature of their of their contact has to be effectively flatter than their eyeball so you need a a larger radius of curvature or a flatter eye i got it okay so you would actually build up the outside of the lens exactly right okay so it's even easier to explain with laser vision correction so let's take a crude analogy which is that the cornea is made out of wood and i have some sandpaper well i can sand down the center of the wooden cornea and take the flaps off and i'm removing some you know some sawdust goes away now that is flatter and so it's less powerful in bending the light and i can focus that on the retina so in your minus one example we would remove about 20 microns of tissue that's not a lot you figure a human human hair is about 50 microns so you know like less than half of one human hair's thickness and prk does that directly with an eczema laser on the very front part of the cornea so we the way we do it is that the very front coating of the cornea is called the epithelium it's a very thin layer kind of like how thick is the epithelium there so it's a it's about again about uh 50 microns something like that 50 55 microns so it's got a basement membrane it's but it's about call it 50 microns so we remove that layer of cells with i the way i do it is with a solution of some eye drops of uh of alcohol and it just sloughs right off and it grows back just like isopropyl alcohol yeah you could use that or ethanol and you so you've anesthetized the eye before doing that obviously that's it's that's a practice builder thank you for that tip how do we get the repeat business yeah i know he's not on the i first that would be really good yeah so you you anesthetize the eye and then you put some alcohol solution on the front of the cornea you remove that epithelial layer which is going to grow back in the same configuration and then you use a very carefully calibrated laser to change the shape of the cornea again dumb question the laser is coming at what angle it's essentially effectively perpendicular to the to the corneas the patient's laying down flat they're on their back and you put something in to wire their eyes we're holding their lid apart are they sedated they're they're i mean i honestly give people valium because it's just sort of an intimidating minute you know it only takes a minute here's what my fear would be in doing it is like my desire to blink would be so overwhelming and break the little eye barrier of course i wouldn't but i'd end up moving my head and you'd zap the wrong part of my eye and i'd be everyone that's everyone's fear you know it turns out valium is undefeated it's just a question of how much but the the it's a very good drug and and so but to address what you you brought up several things there first is a lot of patients fear that they'll do something to to goof up the surgery yeah and there are a number of reasons why that really can't happen but let's go through the procedure from the beginning long before this patient ever laid down on this gurney to have this laser treatment done their eye was digitally mapped using what we refer to as a wavefront sensing device so think about this we send in a very narrow beam of light with a laser and we look at how it bounces back from the cornea it bounces back in a distorted fashion so we send an ideal ray of light in or multiple rays of light in and they bounce back in a distorted fashion the amount of that distortion allows us to map the so you do a topo 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 so we look at the entire distortion pathway and there's more than one way to do this by the way there is a topography based way to do this as well which is very effective but the one i'm describing to you is sort of the easiest one to think of we send in a a known uniform beam of light and look at how it bounces back from the back of the eye that tells us what are the distortions present in this eye how much nearsightedness how much farsightedness but also all of these physics terms of we didn't do this in me right you only do this in someone who's going to be a candidate we may have done it in you just for grins okay we you know we diagnostically this is part of our work up for laser vision correction um and we look at how that how the uh this particular eyeball you know peter tia's right eye distorts light as it goes through the optical pathway this technology was developed for um [Music] telescopes that have to contend with atmospheric distortion so the way this works is that telescopes and i'm talking about like keck the best ones in the world 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 we have the benefit of not having to deal with real-time evolving distortion but we can take a snapshot of what are the distortions of peter's right eye and then we can build them into the laser vision correction that we do on peter's right eye part of doing that means that we have to be able to track your eye so we have to lock onto and register your eye with the with the equipment and any movement that you make part of your fear was i'm going to mess it up well the laser can contract far more rapidly than you can move your eye so while you're doing this patient's eyes can be moving they can and it doesn't matter because the laser is moving i mean it's sort of annoying when they you know so we tell that we coach them hey look at the flashing light yeah but that's really just to keep them in the ballpark of where the tracker can lock on to them i like knowing i'm not the only one that has this really nice ridiculous fear it's not reduced being himself first of all not a ridiculous fear secondly it's universal when i say when i say to patients hey i'm not going to let you do anything to mess this up they're like thank you thank you for saying that that was the thing i was worried about because you know it you don't want someone to laser your eye and you looked off to the side not only are you blind we also gave you a brain tumor that's right so the laser will not fire unless you are within its range of of tracking and it will move faster than you can move so prk is i like your analogy basically changing the shape of this via the mechanism of like kind of it's not sanding it off but it is it's it's vaporizing the tissue and it's a laser that's sort of scanning around the cornea where it does a little treatment here and then we know thermally that we don't want to do another shot right next to that one so we move over here and we want to let the tissue cool down for a few milliseconds and then we go over here so the laser dances around how many minutes approximately does it take does it take longer the worse the prescription is yeah for sure more to shave so like minus two it might be 15 seconds you know yeah maybe it's yeah so minus 10 would be how long like a minute or so you know it depends on the laser it depends on the overall treatment size how much astigmatism and how many are you fixing the astigmatism as well and all the little distortions how much coma trefoil all these these these are physics terms that i didn't really think i would become fluent in but all these little optical distortions that that optical physicists are very familiar with we measure and do our very best to eliminate with laser vision correction so the whole procedure yeah is what half an hour by the time you get the eye get the pres do you know put this thing in the eye put this thing in the eye give them their valium for prk yes um two or three minutes plus the valium time you know it's it's procedure volume an hour before or maybe it's yeah it's like half an hour we have them chew it up and then it works pretty quickly okay so talk about the recovery from prk because one of the things i remember you saying when i was sort of humming and hawing about this was the biggest drawback of prk is the recovery takes longer but you otherwise i think really talked about prk as the gold standard you know i think it's the only reason i might have said gold standard was that it came first it was the first procedure and if you look at prk and lasik which we'll get to in a bit if you look at those procedures say 30 days later they're indistinguishable in terms of results but the lasik patients get there way quicker so prk now i've removed your epithelium so now you have this let's say it's a seven or eight millimeter diameter area of your central cornea that has no epithelium it's like has a that's like having a big corneal abrasion essentially luckily we have drugs drops that can reduce the feeling of the foreign body sensation dramatically so we put those drops on the cornea put a contact lens over the eye like a band-aid it's really like a like a regular soft contact lens and then the epithelium begins to heal from the outside in and that takes 30 days no that takes about four days but here's the thing it's like you know if you were to if you were to have a cut on your arm it would heal over but you'd still be able to detect where that cut was because those cells have not fully remodeled themselves so the cut heals over or the defect in the epithelium heals over in about four days maybe less and then you take the contact lens off you can take the contact lens off then but the vision is still not perfect yet because those cells have to reorient themselves like you know a bunch of orderly bricks in a brick wall and when that when the 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 you from being susceptible to infection which is their job to quickly cover the defect but then it can the body can turn its attention to reorganizing those cells so you do one eye at a time obviously not not with prk or lasik no because because the level of vision typically we do both eyes on the same day because the level of vision is probably about 20 30 or 20 40 within a day or two so when i say the vision the visual recovery takes a while you get pretty good pretty quickly but that last little bit takes several days so you probably could drive a couple maybe two three days later but you wouldn't have 20 20 vision at that point so lasik the only thing i know about that is there's a flap involved that's right 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 cornea when the flap comes back right so 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 a hundred micron flap so we are now under the epithelium so you've taken 20 percent of the cornea up 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 now i open it to page 100 and i'm taking out 100 through 110 and then i close the book the beauty of lasik is that because that that the 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 and that's why lasik was developed post prk presumably as a way to get around the healing process of prk yeah that was sort of a technological race and the way it developed was interesting and some of it was uh in pursuit of more rapid visual recovery so what percentage of corrective eye surgery in the united states today is prk versus lasik i assume the lion's share is lasik yeah i think it's it's it changes but it's probably about 80 to 85 percent 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 more risks in lasik than prk well the risks are are different because the risks of infection with lasik are lower because you don't have this type of way that's right but you introduce another step in the procedure where you now have a flap and that flap can you know 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 you temporarily sever some of the nerves that are sending the signal and eventually over time those nerves typically regrow back and you re-establish that feedback mechanism but i think you get more dry eye with lasik than with prk and for longer 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 what about night vision or low life yeah so that's fascinating they're 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 going to 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 is there a difference in the cost of these procedures i i mean for us no but i'm sure there are some surgeons who charge more for one than the other the the added step of lasik adds some cost but prk has more post-operative care frankly because he requires more visits to to see these folks but we we price them the same what are the uh and how much does it cost by the way i mean it's direction it's probably come down a lot in 20 years right you know i i don't think that it has i think it's been pretty stable i think that you can i think it's probably a about a couple thousand dollars per eye is about the average in north america that you'll find what are the exclusion criteria like who can not who is not a candidate for either one yeah there are certainly contraindications some of them relative but some of them are absolute i'll give you an absolute one there are conditions of the cornea where the cornea is biomechanically unstable where the cornea is actually has a tendency to bow forward in a pathological state and that means that the cornea is not it's a moving target essentially so further biomechanically weakening the cornea makes no sense and doing 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 based on the risk of healing or based on the risk of healing or perhaps the just the overall health of the eye and that sort of extends to people who have other eye diseases like cataract or maybe glaucoma or retinal pathology you are typically operating on healthy eyes when you're doing laser vision correction so if there's some other issue involved you might not be a candidate and is there anything that like well i guess given the differences you've explained why are 15 percent of people still opting for prk well there are certain patients where that's a far better option so we talked about how you're removing pages from a book yep well what if you have a really deep treatment that you need to do and the book is sort of thin to start out with maybe it's better to begin on page one than to begin on page 100. so sometimes the stronger the diopter and the thinner the cornea that might move you more towards pr2 sometimes the thickness of the cornea will dictate it sometimes it might be related to someone with pre-existing dry eye and we're thinking well we have data that these two procedures are about the same in terms of dry eye but our clinical impression is that lasik makes them a little drier so maybe let's do prk on this particular individual um there are and there used to be some restrictions in branches of the military i remember that you couldn't have a flap in your eye if you were a pilot that all went away uh so pretty much every all the 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 um but there are a couple of holdout special forces branches where they don't want you to be a you know i think a maybe an army ranger and that has to do with getting poked in the eye and the possibility that a flap could be damaged and some of this is sort of vestigial lore and it's hard to change the military's rules but they'll just say prk or nothing yeah but that's i'd say that the overwhelming majority of the branches of service allow either treatment and certainly all the commercial airliners you know they allow uh prk or or lasik but the with the caveat that you have to get to the point where you can pass the flight physical so and the same thing's true of people who want to be pilots or aviators they if they need to have 20 20 uncorrected vision to be a pilot they have to have 20 20 vision after laser vision correction is it pretty much a given that you can at least get someone to 2020 after laser corrective vision i mean the way the lasers are built today it's typically the case that you can get them to 2020 or better than 2020 as we were describing before and if you take them to 2015 and they have presbyopia to begin with does it get any worse or is it just that now they're they're noticing it all the time because they never get a break from it they never get to take their glasses off their spectacles so to speak well you know if you if you nail it perfectly so that their prescription is 0.00 i think their distance vision will be phenomenal and their near vision will be whatever it is based upon their age so if they're 50 years old they're probably going to need some near correction some spectacles for reading if they're 41 2 3 4 maybe even 45 they may not need glasses for close up and then you mentioned this smile procedure i haven't heard of that what is that yeah you know it's an interesting procedure it's using a single laser a femtosecond laser and this is 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 that procedure has gained some traction outside the u.s and in the u.s it seems to be an effective procedure i don't i have problem is it solving given how effective lasik is i would say the problem it was designed to solve was dry eye but i think the problem it really solved especially outside the united states was needing two lasers versus one so maintaining and although you could do one with prk you could do one with prk but then you have the the law so it's the prolonged you know recovery time so the idea was could you get lasik like velocity of return of vision with a single laser with a single laser and maybe along the way reduce dry eye yes there are pros and cons to smile you know the technology is evolving i have not seen any data that shows that smile is in any way better than lasik or even equal to lasik frankly but it seems to be a very good procedure are you doing it 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 um we didn't talk about glaucoma yet i know every time i go to an optometrist or even when i came and saw you you is that the one where you blow the air at my eye well that's sort of a that's just an intraocular that's a way of measuring the intraocular pressure that we don't use but 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 the disadvantage to the air puff and it's not really considered 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 with that type of air puff tonometry and we we typically don't use so how do you measure interest you measure it with two ways both of which indent the cornea physically indent the cornea that's why you anesthetize the 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 and what's the definition of glaucoma well glaucoma is probably about a hundred 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 that is somehow related to pressure 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 is too high for them and they can develop damage to their optic nerves and the symptoms of glaucoma are they all this i mean is it always some change in vision is that what would bring someone to attention if they weren't getting a screening 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 i was explaining to a patient that you know glaucoma is totally has no symptoms at all 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 until the very end so and what happens is that your peripheral vision is damaged and most people will not detect 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 but as glaucoma progresses it can affect central vision and then it becomes symptomatic how much of a problem is this in the united states first of all and then in the rest of the world 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 minimally invasive uh basically the uh the management of this has gotten way way better what are like that what's the 80 20 of this what 80 percent of them are caused by what basically 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 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 over production of fluid inside the eye and the pressure is too high inside the eye is the vitreous fluid no it's the aqueous fluid and what causes that is that endocrine is that that may not know we do not know i think this has a multi-factorial pathogenesis there are certainly family history components to this where we see it run throughout families but it's not like inheriting does this run in parallel with diseases like type 2 diabetes or is it uncoupled completely no not really it's not really coupled with diabetes there's some there's some relationship to hypertension but uh you know blood pressure but um ocular hypertension we refer to eye pressure being too high you know you see it in patients who are not hypertensive at all wow the lifelong incidence is what i think you got me there it's i honestly don't know but it's common it's very common we every eye surgeon sees glaucoma patients daily in multiple glaucoma patients daily so um presumably like any neuropathy if you catch it early enough it's fully reversible and if you catch it too late there you you damage it or is it because this is not a center this is a central nerve not a peripheral nerve so i don't yeah yeah i think it's it's you can arrest the progression but i don't think you can undo the damage that has occurred so once there's been optic nerve damage it's not like sciatica no i don't think so i think once there's been damage we expect that damage to remain so it's not unusual for a patient to have what we refer to as a visual field defect so a little area missing from their field of vision and our goal becomes to prevent that from defect from getting any bigger and you can typically do that once you identify it at what age does it start to become enough of a concern that we should be screening for it yeah i think everybody when they go to the eye doctor for a yearly exam gets screened for glaucoma there 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 so if you're screening annually you're you're being checked for you're in good shape yeah you're being checked for it the incidence does go up with age and so in the 50s it's much more important to pay attention to glaucoma and beyond and presumably in the developing world where people aren't going to get eye care or even in the united states if people don't choose to get eye care or can't afford to get eye care it's a bigger risk because they'll only present when they have symptoms that's right that's exactly right yeah all right so to summarize you know again we think about kind of the longevity of the eye is a pretty important thing right if you want to figure out a way to live to a hundred 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 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 yeah those all sound bad 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 we can certainly make a change in our kids so we can make sure that they are outside in natural sunlight right i don't put sunglasses on my kids should i be doing that yeah i mean probably you know it's trying to get a kid to wear sunglasses is tough i we kind of 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 right this would be good yeah it's tough i mean you see kids who are snow skiing for example and they're they should be wearing goggles because those have built-in uv view 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 there's a certain goggles these days are pretty good that's true yeah yeah i that'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 so the trade-off is when in doubt keep them out yeah you know hats are important as well we didn't really talk about that yeah you know i think that that's a very good and effective way but it's not enough because a certain amount of light bounces off and hits the bottom of your cheek and goes right into your eye so it's so for those of us that are now adults basically we've kind of cast our lot uh with respect to that malleable period of changing the the length the well you know we didn't really talk about like what nutritional supplements might have an effect and you know it's interesting because we know that with cataract that vitamin c deficiency is associated with an elevated risk of cataract but it's been shown really conclusively that vitamin c supplementation to supranormal levels does not protect against cataract formation and the things that have been looked at i know a c and e basically antioxidants have been looked at they've had no effect on on cataract formation there is a little bit of mixed weak evidence for lutein and zeaxanthin as possibly being protective for cataract also antioxidants right yes that's correct and you know the macular degeneration we didn't really touch on that very much but that's a huge problem um you may have seen in the drugstore they sell arids a-r-e-d-s formula for macular degeneration that stands for the age-related eye disease study that was again a national eye institute initiative and first they looked at ce and beta-carotene with zinc and a little copper i guess they put the copper in because they were worried about copper deficiency with zinc supplementation and then they got concerned about beta-carotene so they did another study where they took beta-carotene out and put in lutein and zeaxanthin powerful antioxidants and what they showed was that you could delay or reduce the conversion of mild macular degeneration to severe but it had no effect on severe disease and it also interestingly had no effect on people who didn't have macular degeneration it didn't prevent them from prevent them from going on to get it but i think most of us believe that there's something there there's some signal embedded in that noise is light also a big risk for macular degeneration it is it is so again it's this dose thing we want enough light so you don't become nearsighted but not so much that you're frying your retinas and giving yourselves cataracts but i do think that some form of of broad spectrum antioxidant protection makes sense we don't really talk explicitly about screen use yeah is there i mean you talked about a little bit in that study in asia where but i don't know if that was specific to screen use or just it could have been just as much reading yeah it was not specific yeah it wasn't specific to screen use so what do we know about phones specifically in computers yeah so you know this is a super interesting obviously topic and everything from people ask me about blue blocking glasses they ask about am i damaging my eyes am i going to get macular degeneration because i'm looking at a computer screen for 10 hours a day i'll start with the easy ones 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 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 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 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 think about like you have a turtle let's say you take a species of turtle that spends 90 percent of its time in the water 10 on land and we take that and flip it now it's 10 percent 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'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 pm 11 p.m and then asking them to go to sleep is a problem so you know i really try to there's not it's not clear that it's damaging their eyes it's not damaging their retinas or they're giving them cataracts but i think it's messing up circadian rhythms so 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 right thinking it's yeah i mean you know 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 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 like flux or something i love flux yeah you know and flux is free by the way i think for end users and it will take the blue light sequentially out of your monitor as the day goes on as the evening goes on to the point that it's like super amber as you get ready to go to bed i really think that's great 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 to make more sense than the two week ones that you have to wash every night yeah so you know i think the most important thing is you just get them out of the eye we really don't like extended wear contact lenses so whatever type of contact that is 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 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 talked about eye protection yeah you can't again i think we're a little more aware of that now than when we were kids 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 it is interesting that we once word got out in the community that this was something that could be done 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 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 you wore those post cataracts post cataract yeah because there were no implant lenses wow and your prescription was typically about a plus 10. so you know that a minus 10 is a very so there's very there's these people can't see without these glasses that's right and so these are like the coke bottles that and that's where i don't even know spectacles do people even know what coke bottles are anymore so the bottom of a coke bottle is a really thick piece of glass and this would magnify your eyes and make your eyeballs look enormous and then you would have this all sorts of optical distortions because it's very hard to make a super powerful magnifying glass with a long enough focal length peripheral distortion and so you in that context would put off cataract surgery as long as humanly possible so that's really not it's cataract surgery one and done i mean you said it is it should be but do people ever need re-operations 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 is it difficult to get the old lens out since you can't use the same technique to melt it away not really you can just fold it pull it out or so it doesn't cut it and it doesn't re-epithelialize or the the the crispy or whatever the the candy coating of the m m doesn't stick to the new lens a little bit but you can free it up and take it out you can swap out an implant lens it's something that we don't do it it's not like changing your shirt but you you can certainly do it it's another operation one other question i had on the laser surgery i forgot to ask was um do you 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 that's right but the shape of the cornea you're actually fixing so if there's anything that's changing there do you care 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 so we know that the lens is going to 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 so you just have to make sure this length is fixed 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. so does that mean our prescriptions shouldn't be worsening much as we age they really should not be worsening unless you're developing some cataract formation 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 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 going to 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 i didn't mention radiation is another you know we see people who do fluoroscopy like health professionals who are involved and exposed to ionizing radiation i mean if you are the if you're the tech worker if you're the ship captain who smokes uh on a boat that's carrying nuclear waste and you're diabetic you're gonna get cataracts uh a lot sooner a lot sooner yeah 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 right i've ranted on this elsewhere so 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 don't know why i just think the eye is the most sensitive end organ to excessive glycosylated hemoglobin and it's also one of the few things you can look directly at yeah 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 non-invasively non-invasively and um i thought that was really cool i liked knowing that i had beautiful little vasculature background your capillary network was the envy of everyone in the office really really good no but what's what's so like what stands in i mean is there going to be a day when everybody's 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 you're not quote unquote normal right but that might actually reflect higher turnover of rbcs and in reality there's a problem you know so one of the really interesting things about the eyeballs that it's a transparent organ as you point out 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 yeah it's a spleen where you have to use more complicated 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 and that's a very early sign 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 normal individual to have in their lens might that be a screening technique for for diabetic disease but i think probably yes and what about the fact that diabetes manifests primarily as a microvascular disease in so many end organs 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 and again it's not binary right so it's not you know we we we make the diagnosis in a very binary fashion when the hemoglobin a1c it's 6.5 person has type 2 diabetes but you know at 6 percent 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 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 the 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 that 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 is the cost of doing that test if a person said 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 you measured that via pressure or shape as well so the technology to measure glucose in the lens doesn't exist commercially although it's being studied you could look at how the lens essentially reacts to light that you shine 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 we can do that with ocular coherence tomography or optical coherence tomography i should say and we can image in a non-invasive way the capillary network but again i think that's going to hap the changes there would happen after but i bet you see a lot of damage there in people who are unaware of their metabolic state right you do for sure uh and but it's not the canary in the coal mine you're saying that canary in the coal mine is actually going to be the lens distortion due to the osmotic effect of glucose in initial diagnosis and screening yes 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 and we look at their retina and there's no way they're under great control they have fluid exudating into their retina there are what we refer to as hard exudates there are uh micro aneurysms and their mu and their capillary vasculature these are signs that their diabetes is out of control and then we'll say um i i'm glad that your a1c was normal would you mind going back to your doctor and mentioning that we see direct evidence of problems with your microvasculature and it's probably all over and how did the endocrinologist receive that news yeah typically they will accept it they'll say okay well for this individual that level of a1c is not acceptable yeah yeah and they've been typically very receptive because you know they know we can directly visualize i mean look i i this is sort of my soapbox but i really think that ophthalmology should be more integrated into medicine than less because you guys do in some ways operate sort of outside of you know what the surgeons and the internists and endocrinologists do obviously here's an example of where you're kind of saying look i'm seeing something and it's relative it's it's important to your systemic health i i think there should be more of an integration of this i i think again you you you said it earlier and i think people might not have appreciated what you just said you get to directly look at the brain you get to directly look at the central nervous system in a way that an a gastroenterologist can directly look at the colon right that's why colon cancer screening is so freaking effective you get to look with the naked eye directly at a polyp as it becomes cancerous that's one of the reasons i didn't become a gastroenterologist and we are thankful for them because of all they have to say this from absolutely no doubt no but it is amazing that we have the ability to directly observe brain and the vascular tree and so that's that's very very helpful steven this has been super interesting to me i was a little intimidated coming into this one because i didn't have the amount of time i normally have to prepare for this and try to get up to speed on the topic so i came in blind and ignorant but you did a masterful job of accommodating my ignorance and i learned a hell of a lot and i'm sure everybody else did well thanks for having me peter we really appreciate it thank you for listening to this week's episode of the drive if 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Channel: Peter Attia MD

Views: 357,987

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Id: 1SavpBUUy2Q

Length: 169min 17sec (10157 seconds)

Published: Mon Mar 07 2022