 Good morning everybody. I think we'll get started. Our first presenter is Ryan Hogan. He did his undergraduate degree here at Weber State. He's a medical student here at the University of Utah. He's going to talk to us about angle kappa and its importance in refractive surgery. So I want, as he said, my name is Ryan and I'm one of the fourth year students here. I first want to just take the time to thank you all for the opportunity to present a little bit of what review article that is hopefully going to be submitted later this month that I did with Dr. Moshefar on angle kappa and its importance in refractive surgery. I want to take the time to thank Dr. Moshefar and Dr. Mahoptan as well as Dr. Crandall and Dr. Mifflin and Dr. Bernstein for having me with them. Although now that I'm standing up here, I think I'm probably out to go see Dr. DeGree or Dr. Warner because clearly I'm seeing double the amount of people sitting out there that were sitting there when I was comfortably seated in my seat a moment ago. So one thing I want you to keep in mind as I talk about this is this does represent what the current literature says about this topic but this is a very small area of research. And so what the literature says is maybe not exactly what we do in practice or even what is going to be the most recommended. And that's probably just due to the fact that there's a small amount of research out there to represent that and I'll clarify that throughout the study. So like I said this is a review article and there's a picture of me completing the literature review. That's actually about how many papers I ended up reading I think. This was me before and obviously now that I'm done since then I've been applying copious amounts of Rogaine. I've started talking to my razor again and Dr. Katz has fixed my need for those glasses there. So a couple things that you have to understand if you're going to understand Anglicapa and why it's important in refractive surgery and in a lot of ophthalmic surgery in general is what is the difference between the visual axis and the pupillary axis. The visual axis is defined as a straight line that connects a fixation point to the fovea through the eye. Now this as we know there are various refractive indices in the eye that light will pass through and so this is a purely theoretical concept. So we identify this clinically by looking at the corneal light reflex. The pupillary axis on the other hand is a ray of light that will pass through the center of the entrance pupil running perpendicular to the geometric center of the cornea. When you understand this then you can understand Anglicapa because Anglicapa is the angle between these two lines and in most patients in fact almost all patients it will be slightly positive and even superially nasally deviated but when we identify it clinically it's when there is a large discrepancy with a nasal displacement of the corneal reflex from the entrance pupil and who you're going to worry about this primarily in is in hyperopic patients that are severely hyperopic. They tend to have larger Anglicapa values. So here's just a little schematic to help you understand this if I haven't explained it clearly so far. You can see up here the fixation point straight line going straight through the fovea represents the visual axis whereas up here a line passing through the geometric center of the cornea and through the entrance pupil center defines the pupillary axis and clearly the angle between them is Anglicapa. Now if you're looking at this from a corneal topography map or if you're the surgeon looking through the scope this is what you're likely to see in a normal patient. A small amount of deviation between the two with this representing the corneal reflex and that representing the center of the entrance pupil and it's usually superially nasally displaced but in somebody who's a real high hyperop, you know, plus eight plus nine diopters you're more likely to see something like this where there's quite the discrepancy between the two. So why does this matter? Why is it that we care about Anglicapa? The real reason why we care about it in patients who have a large Anglicapa is that this represents a misalignment between the pupillary axis and the visual axis and you can kind of think about it that the pupillary axis since it has everything to do with where light hits the cornea it has to do with the refractive portion that the patient sees the most from whereas the pupillary axis is going to have everything to do with what light, bundle rays end up hitting the retina and what forms the retinal image. So in refractive surgery especially where we're doing things to the cornea and we center these procedures, if we center them on one without regards to the other we set ourselves up for misalignment. This is extremely important in LASIC and PRK and in multifocal IOLs. It may also be important in monofocal IOLs and it's got its importance in pediatrics but I'm not going to talk about those two issues today. So what happens when we don't account for this and we end up getting misalignment of ablation zones in PRK and LASIC? A patient often will come afterwards and complain of ghosting, irregular stigmatism they may even get monocular dyplopia or they can get decreased visual acuity which if we're trying to do a refractive surgery to fix their visual acuity they're not going to be very happy with the outcome. Also if we de-center multifocal IOLs because of the different powers in the concentric rings we can give them photic phenomena most specifically glare and halos. They often are dissatisfied and the lens can actually lose its effectiveness depending on the type of the lens and if it's fairly severe it's one of the indications for explanation of the lens. So the debate for this regularly started about where to center all of refractive procedures really started in the late 80s. There's a paper put out by Yuzato and Geiten that basically said the entrance pupil should be the center of all reference points for refractive surgery and the reason why they said is because obviously the entrance pupil you can easily identify clinically and then as well they cited some work from the early 70s from Inican lattes that showed that the photoreceptors inside the retina actually orient themselves to grow toward the center of the entrance pupil. Well in 1993 Pondie and Hillman came out and they said well actually we probably ought to use the corneal light reflex. They did a pretty complicated study in which they identified what they called the visual axis and then they measured the distance from their visual axis to the geometric center of the cornea that coaxially started corneal light reflex and the entrance pupil and showed that the entrance pupil was the furthest away from the visual axis and the corneal reflex was the closest. They also cited the fact that we shouldn't really center on the entrance pupil because the center of the pupil will change as the pupil dilates and constricts during different light conditions which happen frequently during surgery. So again this is more important in people who have a large angle cap because the distance between these two points is much greater and there's a greater risk for de-centration. So again I said I'm going to talk about this in terms of how it relates to multifocal IOLs, how it relates to LASIC and to PRK. So what does the literature tell us about multifocal IOLs and angle capa? Well the debate started originally with a study where people were looking at this and thinking well I mean these concentric rings have different powers what happens if we end up de-centering them and how does angle capa play into that? So Prakash had all did a study where they looked at predictive factors for patient dissatisfaction with multifocal IOLs and they showed that if a patient had a positive angle capa pre-operatively they had a statistically significant likelihood of complaining of glare, halos and a minor amount of decreased visual acuity. They showed that this was an R-square of 0.26. But then later Woodward at all came out and Woodward said well okay but let's look at all of the reasons why people complain of dissatisfaction with multifocal IOLs. They said that their number one complaint hands down in their study of 60 patients was that people had blurry vision afterwards. They did say okay as some of the people in our study had glare and halos but of those people there were 48 or 41 percent of them but only two of them had de-centration of the lens which is what angle capa would have accounted for. DeVries et al also published a study that was pretty similar that looked at the reason why patients complain about dissatisfaction with multifocal IOLs and they showed again blurry vision hands down number one reason. They said photic phenomenon glare and halo was number two but again of the 29 eyes in their study that had 73 eyes and now only five of those actually had de-centration of the lens. And then Rosales et al published a small paper in which they took aberration models that they generated from human eyes and then they used computer models of those and then they used laser ray tracking of light to see what would happen if you de-centered the lens and they showed that de-centration of the lens probably only minimally contributes to higher order aberrations of the eye. So what do we say about what you should do with multifocal IOLs? Well it's very clear that de-centration of a multifocal IOL is a bad thing and we do not want patients to deal with that and it's decently clear that angle capa probably plays a role in that but it is multifactorial for sure and there's only been one study that's shown that angle capa is predictive of this and it has several issues with it. The study actually included many people in the population that probably had by normative standards what would have been a normal angle capa value. There's always a pretty small study and their statistical significance wasn't that overwhelming. The other thing to consider with this is even though we know that this can contribute to de-centration there is no proven method for a way to offset this. A lot of people will do things like purposely offset it or they've tried even a pupiloplasty to make the pupil larger but none of those has actually been borne out in the literature. However anecdotally understanding the optics of multifocal IOLs it probably is not a bad idea for us to do that and again this is a small topic so there probably just isn't the research there to support it. So what about lasik and angle capa? So I'm going to run through these studies fairly quickly as to not bore you all into tears but a couple things to understand about this is with lasik they also tried to say well you know if the visual axis really applies to the cornea and we're doing work on the cornea if somebody has a large angle capa we probably ought to try and see if it is more effective to center on the corneal reflex. So this series of studies set out to do that exact thing. So Boxer et al came out and this was a case report where a gentleman had bilateral angle capa and needed lasik in both eyes so they said okay we're going to center one on the entrance pupil and one on the corneal reflex. They did this and in all measures that they recorded the eye that was centered on the corneal reflex did significantly better post-operatively. Then Pemko came out in 2004 and they said okay let's do a retrospective review and see if all the people that we've tried to center on the corneal reflex was it safe and effective and they were able to show that in no way threatened best spectacle corrected visual acuity or best spectacle corrected contrast sensitivity post-operatively. Then Chan and Boxer came out and they did a study where they measured the theoretical amount of decentration that would happen if you centered on the entrance pupil versus centering on the corneal reflex and showed that theoretically decentration was more likely to be larger if you centered on the entrance pupil. Then Dior Tueta came out and they actually said okay well let's not try the entrance or the corneal reflex let's try the corneal vertex which is the highest topographical point of the cornea and it lies very close to the corneal reflex and they showed that it was safe and effective as well. Then Karimani came out and they actually did a study where they compared retrospectively centering on the entrance pupil to a distance halfway in between the corneal reflex and the entrance pupil and they showed that it again had good uncorrected visual acuity and in no way was dangerous. Solar et al. in 2011 came out with a study which was the first randomized double blind which or double mast I'm sorry which I don't understand how they mast it to be honest but they compared entrance pupil versus centering on the corneal reflex and showed statistically there was no difference but the corneal reflex tended to have better uncorrected visual acuity after surgery. Then Canopolis did a study where they said we're going to purposely center on the corneal reflex in all patients that have angle kappa and retrospectively look at what happened. They looked at 212 patients and again showed they compared to the patients they had centered on the entrance pupil versus the corneal reflex there was no statistical difference but again tended to have a slight increase in uncorrected visual acuity. So what do we say about what you should do for Lasik? It's pretty clear that centering on the corneal reflex or a distance halfway in between the corneal reflex and the pupillary center is safe and probably a better bet than centering on the entrance pupil because even though there's no trial that specifically shows that centering on the entrance pupil is dangerous we have seen a couple of case reports where when they did that they had worse outcomes than if they were centered on the corneal reflex and quite simply there's more research needed in this area to fully clarify this. So what about PRK and angle kappa? The first thing to understand is that the data on this is about as limited as it comes. There are several trials and none of them even specifically address the idea of angle kappa but the idea of centering over the corneal reflex versus the entrance pupil is addressed. Kavanaugh at all was the first to do this in 1993. They did PRK on a bunch of people and they said well as decentration isn't more than a millimeter post operatively than all of our patients and there were about 145 of them I believe had an uncorrected visual acuity of 2020 and we had best spectacle corrected visual acuity that was preserved. Again this doesn't specifically address angle kappa but it's along the same lines due to the differences in centeration points. And Kim at all came and they said well we're going to measure post op decentration from three different methods. They looked at the corneal reflex with the surgeon looking through both lenses in the scope. They looked at centering on the corneal reflex at the surgeon looking just through the left eye of the scope and they centered on the corneal or on the entrance pupil with the surgeon looking just through the left eye of the scope. They did this they showed that the most amount of decentration happened when you centered on the corneal reflex viewing from the left eye only. However that likely had to do with the fact that they looked at a lot of right eyes through the left lens of the scope. And then Rheinstein et al had a case report that they reported in 2011 where a person had a large angle kappa had previously had an RK had an irregular corneal surface and they said well what should we do in order to do PRK on them. They looked at the aberration model and saw if you center it on the pupil this is going to give him something that's not going to fix his problem and actually probably make it worse. They looked at the topography guided model and saw which is centered on the corneal reflex and saw that it was probably going to fix his problem better so they did that and the patient had an increase in his uncorrected visual acuity and a symptomatic report that his symptoms had decreased drastically. So what we say for PRK is the evidence isn't really there for one or the other but what we know is that centering on the entrance pupil is safe but not necessarily tested in angle kappa. Centering on the corneal reflex however is probably a better bet considering that there's plenty of evidence to show that it's safe and effective in Lasik and the principle behind Lasik and PRK are essentially the same. Again this is inconclusive and we need more research to fully understand this. So the conclusions and what I want you to take away from this is that this is important for all people who are doing any surgery on the eye because this may also be important in simple cataract surgery. If you're aligning the refractive power with the center of the pupil and they have a large angle kappa you may predispose the person to having glare and halos afterwards and if you're a refractive surgeon this is definitely something that you need to consider. For multifocal IOLs the evidence is not there to suggest that we have to do anything or even anything that we do is going to be effective or anecdotally it probably is not a bad idea and Lasik patients who have a large angle kappa is very likely that centering on the corneal reflex or a point halfway in between the entrance pupil and the corneal reflex is the best option. And then in PRK even though the evidence is not there to suggest centering on the corneal reflex it's likely that because the evidence is there for Lasik it is also probably the best approach. And then what is really needed now is we need large head-to-head trials that compare the differing centering methods of entrance pupil, corneal reflex, corneal vertex and a difference halfway in between with varying levels of angle kappa or sub-analysis that would tell us specifically that a patient has an angle kappa this large this is the best treatment for them. That's the rest of my talk. Here's my references. Questions? Yes, James. So you can center on the corneal reflex when you look through the scope. Depending on what your machine is the machine actually has a platform and it lets you pick where you center the ablation zone for Lasik and PRK and so you have to kind of manually as far as I understand punch it into the computer or move it over to where the corneal reflex is instead of centering it on the entrance. I believe so. And so wherever you choose to center it is where the computer will center the ablation zone. Yeah, and it's actually important that you point that out because when I presented the original debate the people who argue for centering refractive surgery on the corneal reflex, Pondie and Hillman back in 1993, when they measured the distance from where they defined the visual axis to be, they showed that the geometric center of the cornea was the space that was the furthest away from that. Further away even in the entrance pupil and the corneal reflex. So that's a very good point. And like I said, I didn't delve in too much into where exactly for monofocal IOLs that you should center but that's a good point to keep in mind for even that when you're making the rexis that it should be centered on where the patient is going to see it the most. Yeah, and unfortunately the literature just isn't there to support that. I mean, and I would totally agree with you. I think that that's another place where we need some more research for TORC lens specifically to show that this is important to consider as well. Thank you so much for your time.