 Welcome. Good morning. I have to be in surgery in a half an hour. So I think Eileen queried you guys and let you know. We have actually like I think four refractive surgery lectures, so we've got plenty of time to cover stuff. And I'm definitely interested in trying to actually teach you guys something that's not on all the canned lectures and I think the BCSC book is actually really good. So if you read that, you'll learn a lot and it's really applicable. One nice thing about refractive surgery it's actually very applicable to many of the things you do. Certainly all areas of anterior segment, refraction, contact lens fitting, etc. So it's nice from that standpoint that there's not a lot of esoteric stuff. It's pretty much nuts and bolts. So one thing about sometimes I feel like refractive surgeons are like or maybe corneas specialists are like orthopedic surgeons of ophthalmology. It's like pretty basic. We can count to four. Orthopedic surgeons can only count to three. That's one different, but really the basic things. I mean, it's structural. It's physics. But refractive surgery within that is a little different in that it's super, super precision oriented for one thing. It is kind of like oculoplastics in a way and it's, you know, it's fee-for-service, self-pay. So very high demand for perfection basically. And so if you can really set yourself up for failure, if you're not, if you cannot deliver the good, so to speak. But as I mentioned before, there's a lot of overlap with other things that we do all the time. Cataract surgery has become very, very much thought to be, at least by the the consumer, if you will, to be a form of refractive surgery. And corneal surgery is also very precise and very physics-based. And then, you know, finally, glasses and contact lenses are really important in what we do. And if you understand this stuff, it really helps you understand that as well. So again, we're not going to cover all of the assigned reading. You can kind of go through that. Again, we have about three more lectures after this. So if you have questions, one of the things I'm going to do is have like Q&A in those lectures. And so we'll let's see. So since Eileen's on the service now is what we could do is just email. If you have questions or things that you don't understand, email Eileen and she'll get it to me and we'll talk about it a little bit at the beginning of the next lecture. And I know that there will be things that people don't understand because, you know, there's lots of material. One of the, I think the biggest pitfalls in refractive surgery and also just in ophthalmology in general, and this is particularly pertinent to people who are in training, is you over-trust technology. It's like, you know, we have all these gadgets and machines and but your brain is still way better in terms of, you know, just kind of figuring out what makes sense and what's going to make the patient happy. So I really feel like that's an important point that I want you to take home is that just because an imager or a machine says that this is the shape of the eye or whatever, that is a perception. That's a data point. There's error in any measurement. And so it's really, really important to look at the big picture and the bulk of the evidence. And then one of my favorite expressions in surgery and it applies to, you know, things like hunting or target shooting. But if you're aiming for precision outcome, you're going to miss every single time. But if you're aiming small, then you're going to miss small. And that's a really good, really good concept for eye surgery. It doesn't matter what kind of surgery it is. If it's retina surgery, if it's cataract surgery, if it's refractive surgery, it's particularly important with refractive surgery. And then I think there's another really interesting aspect of refractive surgery in that it, because it is fee for service and it can be very lucrative, it is also has some potential for abuse in terms of maybe doing things that you really shouldn't do or kind of, you know, pushing the edge of the envelope a little bit and saying, I can get away with that and, you know, the patient's going to be gone and I think it'll be fine. But so number two, this applies to refractive surgery, but it also applies to everything you do as a physician. And I can think of, you know, my three reasons why it's not ever a good idea to compromise your patient's best interest. And this could apply to signing up a cataract at the VA or, you know, doing refractive surgery on some VIP or whatever. But number one is that, you know, it's just not the right thing to do. And at the end of the day, all you have is your integrity, you know, you got to go home and go to bed and feel good about yourself. And as a doctor, you know, you're going to make mistakes, you're going to have bad outcomes, you're going to have a lot of good outcomes as an ophthalmologist. You're going to help a lot of people. But if you kind of do things for the wrong reason, it takes away some of that great satisfaction that we get from the privilege of being a doctor. So just for your own integrity, just, you know, just choose not to do those things. You're going to make plenty of money and have plenty of success and you really don't need to even go there. Number two is that those kind of things definitely come back to you, you know, so if you kind of bend the rules a little bit, we all learn this when we're little kids, you know, a little libe, he gets a big lie or whatever. But really, if you're in practice and you have a reputation, it's really you have to take the long view. And if you do the right things for people, even if sometimes it's telling them no, that is really going to come back to you in, you know, in an exponential fashion as to just being a good provider. And that kind of word of mouth referral system to your practice is amazing. And, you know, it's not hard to stand out. Unfortunately, it's not hard to be someone who's viewed as a person of integrity and, you know, in our modern world. It's unfortunate. But so I think if you do that, and then, you know, the third one is maybe the least important, but just a practical thing is that, you know, everything you do is going to be scrutinized by kind of medical legal things and, you know, regulatory things. And you guys are coming up into a generation of practice where that's just the reality is everything's going to be measured outcomes scrutinized. You know, everybody is going to take a video of every surgery you do, you know, if they're watching on a monitor or whatever. And so you want to make yourself basically bulletproof. You want to make yourself, you know, you want you need to be able to continue practicing and do what you do. So another really important concept is to be very systematic about how you do refractive surgery. More so probably than other things because there are really a lot of reps. And that, and it's a little bit like cataract surgery, too, but it's a little bit more predictable and precise. But you really learn from your little tiny mistakes. And if you do things the same way and you're very dogmatic about your system, not dogmatic about how you treat every patient but your system, then you can adjust your system to approach perfection. So I did my residency and fellowship here. That was a long time ago. But in my fellowship, I had mentors, Dr. Olson, who was amazing, smart, probably still the smartest man I know, at least one of them. Dr. Claren Aldridge, some of you might know, is just amazing, amazing cornea specialist and surgeon. I learned so much from him and, you know, both men of super high integrity and just great examples. And then Tom Clinch, who was kind of the junior person, and I learned a lot from our mutual mistakes. And but, you know, he was a great teacher as well, because he was kind of young and learning things and not afraid to try things. And, you know, also a very good provider. But most of all, more than any, I learned from Charles Casper, who was, if you read about him and the history of ophthalmology and refractive surgery, he was a real radial keratotomy pioneer, which we know was kind of a bad surgery turned out to be not such a good thing. And you can read about that in the BCS book. But he was an amazing example to me, just in terms of how one should practice as kind of a leader of a team. And also this systematized approach to vision correction surgery. And he really, he kind of set the tone for that. And there's even a, you know, an ISRS named lecture after him, because he was kind of the person who really made teaching refractive surgery a science. And his whole thing was you got to have a system. And so, one of the most important things about vision correction surgery is you really have to understand if you're going to do something to the eye, what effect is it going to have. So, so you really need to understand the anatomy of physics. And you have to think logically about okay, if I do this, what's going to happen, you know, take into consideration what's going to happen when it heals, things like that. So even though he was kind of a proponent of some kind of crazy things that didn't work out very well, he really, you know, he understood that hey, I got to like really understand what I'm trying to do, and then be very systematic about it. And then preparation, he was actually a military person and a pilot. And so, you know, pilots, if the airplane doesn't perform right, or if they don't do their job, they might crash and die. So, you know, it's like every flight, you don't skip any steps, right? And so that was his point with vision correction surgery as well, is that you really have to, you know, just kind of be completely thorough and go through everything like three times before you actually start the surgery. And then the other things are, you know, somewhat self-explanatory. If you don't standardize your technique, you're not going to be able to compare, you know, one patient to another outcomes. And if you don't measure your results, you're not going to get that data. And then probably most importantly is, doesn't matter what you do technically, that is, you know, we should all be able to do that. Refractive surgery is not really hard surgery, technically. But just, you know, investing in making a great staff, having people be kind of mission oriented, like, okay, our mission is to serve our patients and make them happy and give them really good vision. It's kind of an obvious thing, but it's really important. And you don't really see it in training as much as you should, because, you know, it's a big institution. And I think that gets watered down a little bit. I kind of call it the lowest common denominator factor of being in an institution, because, you know, you have all of these things that kind of can sometimes keep you from being as excellent as you'd like to be. But, you know, it all starts with the people and case bearer, you know, he really rewarded his staff, he really took interest in them, and he really cared about them. And in turn, you know, that was transmitted to the patients. And, you know, I would, as a fellow, you were just like the dumping ground of everything, you know, call 24-7, all these complications or whatever. But the patients always thought, hey, I'm doing great. This is awesome. I mean, and it's not brainwashing, it's just having that positive attitude and really caring people, you know, kind of saying, hey, yeah, you're, you know, you're having this struggle, but you're way better than you were. And so it's really important how you present things to patients. And, you know, most of all just care about them. Medicine is a caring profession. So, you know, just regular, ask just kind of some of the benefits of being a refractive surgeon or incorporating that into your practice is that it is a very functional thing. I mean, I had a patient, and this was actually a clear lens surgery that I did. I saw her yesterday. She was in her 50s, I think, had a little early cataract. And she went from minus 15 plus to 2040 in her worst eye to 2025 uncorrected. And she's 20-20 plus in her other eye, which was, you know, minus 13 or something. And so, you know, I mean, it's just completely life-changing for people when you can do that kind of surgery. And it is very functional for people in our area. You know, so many people struggle with dry eyes and don't tolerate their contacts well, sports, et cetera, et cetera. You can just go on and on. There's a high demand for vision correction surgery. People want it. They like it, you know. They, for a lot of those reasons, it's a very gratifying surgery to perform, just like some of you are starting to perform cataract surgery. That's way cool to, like, take some, you know, person, you know, 2200 and take their cataract out in their 20-20 the next day. Well, that's how vision correction surgery is, but maybe even better because it's a little bit more precise. Usually, the patients don't have a lot of comorbidities. And so it's really, it's really cool. It's fun surgery. It's high tech. All these good toys to play with. And generally, it's a very upbeat atmosphere. And again, lots of new stuff, things to learn, and it's financially rewarding. I mean, it's a very lucrative surgery to perform. So if you choose to incorporate that into your practice, you don't have to deal with, you know, third-party payers, reimbursement, regulatory stuff. It's fee-for-service. So now we'll kind of delve into some of the, just some of the stuff in the basic science books. And this is, some of this is in the lecture that's already in the system, but I just cut it down because we don't have enough time today to go over all of it. But I really would encourage you to read through that book and look at the, the figures are actually really good in the book. Most of them are good. And there are some really important concepts. And so we'll just cover a few of them. So, so everybody knows that the cornea is the main refractive surface or lens of the eye. And hopefully we all understand how light is bent by the cornea. We're not going to spend a whole lot of time by that. Well, let's start with basic. So we know how the light is bent by the anterior surface of the eye. Does anybody understand or have a question about how light is bent by the posterior surface of the cornea? Remember that the anterior surface is an air cornea, you know, tissue interface. And so the index of refraction is pretty different. But what about the posterior surface of the cornea? If you can explain that, who understands that? Renee, you want to take a stab at it? No penalty for getting it wrong. I mean, these are kind of the important structural things that you just kind of want to understand, because it'll definitely show up on OCAPs and boards, things like this. So if you think about the curvature of the eye, they're both convex lenses, right? The anterior and posterior surface. But the index of refraction, you're going, you know, from cornea, which is a little bit more dense optically to aqueous on the posterior surface. So we can all visualize that the anterior surface converges light, right? You understand that? It smells, law and everything. The posterior surface will diverge light a little bit. So as Renee said, it's a minus lens. And so is that super important in refractive surgery? Surprisingly not at all, because it doesn't really matter for vision correction surgery very much, because you're just treating the whole refractive error. But what about cataract surgery? Why is it important for cataract surgery? Right. I don't know if you guys could all hear that, but so you can tell Julia's, you know, she's in the, you know, the seniors are like doing cataract surgery and choosing lenses and choosing toric lenses. And so it's like all this stuff you have to try to figure out to get a good outcome. I mean, people, that's fee for service. Well, at the VA it's not, but, but you know, in the real world it is. And so you really want to figure it out. So in general, so in it's, I think one of the important things about learning is like, you don't even really have to understand it completely. You can always kind of work backwards. But just know, so the take home points are posterior cornea does that aqueous corneal interface does diverge light. So it gives it, it subtracts a little bit from the corneal power. And so you have people all to say, well, it's 48 minus six in this slide. So it's 42. And that's where you get kind of that average value that's on the caratometer. So that's just kind of adjusted for the posterior cornea. And then the other really important take home message is how is that posterior corneal power usually oriented? Does anybody want to volunteer that one? So it's usually against the rule. So, so if you have so, so again, sometimes working backwards is the best way. So if you have a patient and they have with the rule of stigmatism, which most people know means, you know, more vertically oriented cylinder axis towards 90, and you're going to put a toric lens and you're choosing a toric lens, how would you adjust it for the average patient? Right. So, so again, take home message, this would show up on OCAPS for sure. You know, I can see this being a question. On average, do you under correct or over correct with a toric lens when the person has with the rule of stigmatism? The answer is, you would under correct because you expect them to have some kind of thinking of it as plus cylinder refraction against the rule more at 180. It's going to counteract some of what you're measuring. And so, even if you don't understand all of it, and you can kind of think about the ray tracing and all that, the take home message is if you kind of get there, then you're like, okay, you're halfway, and then you can work backward. The lens is also important, but not as important. And, you know, again, in refractive surgery, it's kind of nice because we're just really working on the total power of the eye. So it's a little bit easier in a lot of ways than cataract surgery. And it's definitely more precise. An important concept, just, you know, another really important concept in is to understand asphiricity. And it's important for corneal surgery. It's important for refractive surgery. It's important for cataract surgery. So this you can kind of think about too. And I'm not going to really talk about spherical aberration a lot. We don't have time to go through that. But the eye kind of naturally adjusts for spherical aberration. So if the cornea is really flattened out, and again, this is more of a take home message. So this would be like a radial keratotomy. It's actually more like an RKI than a lasik eye. But you could say a myopic lasik eye. The peripheral light is going to be bent a lot. These light rays coming centrally are not going to be bent as much. And you're going to get what's called an oblate cornea. It's flat on top. And so you can have to kind of take that into account in terms of quality vision and contrast. The normal cornea is more prolate. It's actually a little bit parabolic. So it's going to be a little bit steeper in the center than in the periphery. And that's the reason is because the peripheral light will be bent more. And that's what causes spherical aberration. So you can think about evolution. You can think about intelligent design. You can think about whatever you want to think about. But there is a reason that our eye is that way. And most people's eye is prolate. And we want to preserve that prolate. So those are probably two of the most important things that you can understand about. Just the cornea is understanding there's some influence from the posterior surface and then what's prolate and what's oblate. Topography definitely important. Super important. We use it all the time. So it's also really, really important to just understand basics about topography and tomography. Everybody knows placido disc is the reflective image that is used to generate most topographies. There are topographers now that project dots of light. We're not going to go into that. We're going to stick with the basics. But same principle, whether it's dots of light or rings, it's a simple reflection. And then the distance between the rings can be analyzed by the computer. And how many of you, many of you do, but how many of you have ever read a topographic map or have used a topographic map while hiking? So you know that a cliff is going to be a bunch of lines really close together. So again, just really, really basic stuff. But you need to understand that for refractive surgery, cataract surgery, cornea stuff. So if the lines are close together, it's really steep there. And it's really as simple as that. It's not that crazy. So the regularity of the pattern, the pattern, topography gives you pattern. And the pattern data is really what you're looking for in topography. It's not as good quantitatively as some of the other measurements. But pattern is everything because you're really trying to find diseases like keratoconus. And this is kind of, we would call it a non-orthogonal or kind of a sagging bowtie picture. The keratometry values are really super normal range, 45, low astigmatism, 1.5. But this person would be somebody that you would say, hmm, I wonder if that's normal or safe enough to do vision correction surgery on. You would need to do more tests to find out. But it would raise some suspicion. So pattern is really, really important for topography. And again, we kind of can spend time on this, but it's better to just read about it. And this could be something we could talk about in one of the follow-ups. But kind of understanding just really briefly the difference between the two common ways of looking at placido topography is the axial or sagittal power and then the tangential power. And one good way to think about it is, you know, if you're looking at the axial power, your reference point is the top of the mountain. So if you're up at snowbird and you're kind of deciding which way to go down, you're kind of looking at, well, that looks pretty steep. I'm not going to go that way or whatever. As opposed to tangential, where you're actually down on that next run saying, okay, this is pretty steep. And so the tangential gives you a little more kind of detail at the site. The axial gives you more of an overview. And if you understand it to that level, that's probably all you need to do. Don't worry about all the diagrams and stuff in the book. Not going to get asked that on the test. The other major type of imaging is called tomography, which we would all understand based on, you know, regular imaging in the body, CT. So this is just optical CT in a way. And the images can be captured in, and for historical purposes, you should know about Orbscan. Orbscan is kind of a scanning slit that moves across the eye and computer captures the data. And just it's kind of like a slit lamp beam. And you can just basically tell from that when it's reconstructed 3D shape. But a better form is called Shimeflug, which is a video camera that just spins and takes pictures from all different angles to reconstruct it. And so that's Pentacam and other things, but considered to be more of the gold standard. This would be just probably kind of the really, if you can kind of understand, you can get overwhelmed with maps and presentations of some of this data. But this is called the holiday view on Pentacam. And this again would be something that could show up on OCAPS or a test or something because it's just very standardized. And tomography data will always give you thickness. And so the thickness data is almost always represented in the center with the top being absolute and the bottom being relative. So relative to a reference point, you know, color changes are just used to represent, you know, again, what does that ski slope look like? Where's the steepest or thinnest areas? Where's the snow, the thinnest, if you will. And these two are just like the topography axial or sagittal and tangential curvature. So they just kind of, it's just another way of looking at what you get from your topographer. And then the most important thing, and this is really, really important to understand is the posterior cornea is can be a stumbling block in refractive surgery. And so again, this would be one of the most important take home messages of the whole lecture today is that the posterior cornea can be hiding abnormalities. And they may not show up on screening tests or refraction or anything like that. And so, and because laser vision correction surgery removes tissue from the cornea, you can actually create a huge problem. You can cause care to conus or we call it corneal ectasia. So it's really, really important to understand these maps. So in the few minutes that remain, actually, I'm supposed to be in surgery. But so this will be the last point of this. These are just the tomographic images compared to a reference surface. And almost everybody has a stigmatism. So we talk about best fit surfaces. So you'll see BFS sometimes, which is best fit sphere, but it's almost always compared to the best fit toric elliptical front. So that just means a dome shape that's closest to the amount of the stigmatism that they have. And you're comparing the anterior and posterior surfaces. And these are just values in microns. And so this person has a really symmetric anterior cornea. Almost no, you know, that's just noise. A couple microns. You can't. And the posterior cornea is actually really normal. Now there's little something there. Plus 17 means that that's 17 millimeters higher than the reference shape. But usually when you get out here, it's just noise, you know, there's tear film or something like that. So that's a super normal thing. So we can do more in the next slide. I'll be happy to, you know, take questions. We didn't get to wavefront today. But that's another thing to read about. Make sure you understand aberrometry and wavefront. And if you don't, so topography, tomography, just kind of how the cornea bends light, wavefront, you don't really need to understand all of this stuff. Focus on spherical aberration. That's probably the most important thing to understand because it really applies to cataract surgery as well. We'll go more into that. Yeah. And that's actually, so read about it, see what specific questions you have. But if you read about wavefront scanning and then aberrometry, I think you'll, and then we can like hone it down to what's practical about it. I mean, I think that's one of my goals for this year is to just really figure out what's practical about all this stuff because there's a ton of good practical information. All right guys, thanks a lot.