Lecture: Orthokeratology: Troubleshooting Patient Cases

Orthokeratology contact lenses are becoming increasingly popular as a method of slowing the progression of myopia in children as well as providing reversible corrected day time vision. In this live webinar, Dr. Levine follows on from this year’s earlier introductory orthokeratology webinar, by presenting patient cases and the common pitfalls when fitting orthokeratology lenses.

Lecturer: Paul E. Levine OD, FIAO, FAAO, Vision Care Specialists, Boston, USA


DR LEVINE: My name is Paul Levine. I practice in Southborough, Massachusetts, in the United States. I know we probably have several international people joining us this morning or this afternoon, depending on your time zone. And I appreciate that, and I hope to be able to get through a lot of the basic troubleshooting and things you can kind of look for, and look out for, when it comes to doing orthokeratology. Just a quick little disclosure here. I am the president of the American Academy of Orthokeratology and Myopia Control, which is a volunteer position, and there are no commercial biases during this presentation. We’re gonna talk about what to do when your OrthoK fits don’t go exactly as planned, and that can occur in either less than optimal lens positions, and also the adverse physiological responses that sometimes we have to watch out for, if you have a… So here’s the first question I have for the attendees here today. How many OrthoK fits have you performed to date? Just so I get a sense of what my audience is, and what your level of experience is. So we’ll give you about 15 or 20 seconds to click on those buttons. Okay. So about 62% of the response is no fits, 23% under 20, so we’re talking about basically almost 85% of you have done fewer than 20 fits, and a we have a couple of experts here, at the 100+. So that tells us we can keep things basic, but we’ll also get into some more intermediate and maybe we’ll touch a little bit on some advanced issues. So the first thing I just want to talk about: When it comes to troubleshooting, the first way you troubleshoot is to know what kind of trouble you might potentially be getting into. And so you want to do as much as you can before the fit even starts, so that you can anticipate things that may not go perfectly well or go right or how things are gonna go. So the first question always people ask, especially new fitters to OrthoK, is: Do I really need a corneal topographer? And the simple answer is no you don’t. You could take K readings and you could take refraction and call a lab and they’ll send you lenses. But the problem is, when you need to troubleshoot, the topography couldn’t be more important for telling you what position those lenses ride in, when the patient is asleep. You can put a lens on an eye, and you can put fluorescein underneath that lens, so that you can look at the topography pattern, and help that guide your fitting, but there are a couple of problems with fluorescein patterns. The first is that fluorescein doesn’t fluoresce, if it’s less than 20 microns thick. So if you have a lens that is displaying areas on the cornea that are black, they may not actually be touching. It just may be that there’s not enough fluorescein there for you to see. There may be only 5 or 10 microns of fluorescein, so it’s not as accurate as would you like to be. The other problem is that if patients are sitting upright, they’re leaning into the slit lamp, you’re looking at them, and the lenses are moving every time they blink, so you don’t understand how that lens will position itself, once the patient is asleep. So the topography after the wearing is really important, to see how that lens is centered. Most topographers nowadays, the Placido disc topographers, are measuring 9 millimeters. But the Scheimpflug ones can get up to 12 millimeters. The topographical data represents the central 3 millimeters of this cornea, but when you open up to the 9 millimeter, you can see that this clearly is a cornea that you should probably stay away from, when you’re doing OrthoK, because of how asymmetrical it is. Probably an example of pellucid degeneration there. So I can’t state enough how important topography is, and how important your initial topographies are. You only have the one chance to get your first topography, and your first topography is how you make all your decisions as to what that lens is gonna be. You know, what parameters you want to adjust in that lens. So this is an example of a good topography. You can see that the rings are nice and even and clear, and the topography data looks decent. Now, this same eye captured a moment or two later — you can see that the tear film was starting to break up. As you can see on the left, and you can see what that does to the topography on the right. And so that starts to corrupt the data. This is another example of a bad topography, where you have tremendous shadowing from the upper and lower eyelids. These are really common, especially with your Asian patients, and you have to really do your darndest to get those lids up and out of the way, when you’re getting these first initial topographies. So there’s a question on the floor that I will just answer live. Which is: Is there a preferred model of corneal topographer for OrthoK fitting? Not really. I would say that the industry generally uses the Medmont E300 as kind of the gold standard in corneal topography. The keratograph by Oculus is a major player in this space now, and the Keratron Scout — those are probably the three biggies that most experts use. This image that you’re looking at here was captured with the Keratron Scout. But any topography is better than no topography. If you have a topographer, and you’re not in the — it’s not in your budget to replace it, if it’s not one of the three I mentioned, you can still do just fine with what you have. If you’re looking to buy one, you might want to seriously consider those three that I just mentioned. And I just want to touch really quickly — I know that Dr. Watanabe already gave a lecture of what the basics of OrthoK are, but just because I’m gonna be showing so many of these types of screens, I just wanted to repeat that there are a few forces at work during OrthoK. You have the downward force, centrally, which creates our treatment zone, which is the flat zone in the center. So we have… Just bear with me for a moment. So we’ve got it — right here is our treatment zone. And then we have the red area. Which you can see is — where the lens lifts up a bit. I’m trying to just see if I can get this… Annotation to work. But it doesn’t seem to be giving me exactly what I want. At any rate, you can see we have downward pressure, which is, as the eyelids push that lens toward the eye, and then you have a negative suction, or a sucking force that pulls the cornea up into the reverse curve, and then you have your landing zone. And there’s a question about SPK, but we’re gonna talk about that a little bit later. And then here’s, again, just another look at how our lens on eye will translate to topographical changes. And we’re gonna talk in just a moment about the anatomy of the OrthoK lens, so we’ll get into those parts in just a moment. So when it comes to trouble shooting, there are a few different things that you can do. The first is you just have to take a step back sometimes, and try to understand where things went wrong. You can call colleagues. One of the things that I found very helpful, when I first started with OrthoK, is I had a group of friends that were at varying degrees of proficiency with OrthoK, and we would share cases, and we would go over issues that we were having, and we would try to come up with solutions to help each other, and then your lab consultants are also very, very, very important. The lab consultants really are experts on whichever lens you choose to use. So I do encourage you to speak with your lab consultants, if you start getting into a little bit of trouble with the fit. And then some of the best education that you can get is if you go to an OrthoK meeting, the time spent in the lounge, after the day’s lectures, oftentimes is when you can almost learn the most about doing this. And people who do OrthoK tend to like to share. So we get a lot of after-hours education done, to be sure. One of the things that I really stress is using your retinoscope. The retinoscope is a very important piece of equipment. Not only does it tell you what you need to know about the refractive condition of that eyeball, but it also tells you about the position of the treatment zone, and you’ll see in the next slide — if this video will start playing — you’ll see as I’m scoping the eye, you can actually see the treatment zone within that pupil. I think hopefully you can all see that. Fortunately, this patient had a large — larger than average pupil. Which really makes seeing that treatment zone kind of pop right out at you. So I find that’s a really important thing to do. Especially when you have decentered topographies, which I’ll show you some examples of a little later. This is just, again, looking at that same treatment zone, centered inside that pupil, which you can see in the topography pattern. The black circle represents the pupil, and you can see where we’ve got that well-defined treatment zone, right in the center. So please remember to use that retinoscope for more than just figuring out what the power of that eye is. So when it comes to troubleshooting, you need to understand the lens. So… Just hold on one moment, please. (phone ringing) I apologize for the phone ringing in the background. Sorry about that. The anatomy of an OrthoK lens. You’ll see on the left the actual picture of the lens on eye, with the fluorescein pattern, and you see on the right an OCT that I took of that lens, and you can clearly see that the treatment zone, which is the center, creates an applanation to the center of the cornea. You can then also see, if we jump to the next component, we’re now looking at the reverse curve of the lens. And you can see the reverse curve in the OCT is quite a bit steeper than the base curve, which is very flat. And that’s extremely important, because that is where that negative suction force occurs. The alignment curve or the alignment zone of the lens is where the lens touches back down onto the cornea. So again, flatter than the reverse curve, but steeper than the base curve, because the base curve is typically flatter than K, and then the alignment curve is really very important. This is where the lens holds its place, assists in centration, and it assists in the suction forces that need to occur underneath that lens. And it’s really important to get a seal in that zone, 360 degrees around. That’s how we get this water seal in the lens that assists the hydraulic forces needed to reshape that cornea. And then the last zone that we talk about is the peripheral curve, or the edge lift, if you will. And you can see that that lens just starts lifting up. A little bit off the cornea. But not so much that it causes a flared edge, which could be uncomfortable. There’s a question that I’ll address right now. It says that the treatment zone is different when the eyes close, as the lid pushes the lens. So I guess to know the real position of the lens, only the topography could do the job. The ret would only help when the eyes are open. That is true, but remember that the ret is done after the lens had already been long worn and taken off the eye. So this was like… This was the naked eye that — that video I took of the retinoscopy reflex was of the eye after it had been molded. I hope that answers the question. So now we will get into some actual troubleshooting. And some malpositioning of lenses. So you can see in this particular example we’ve got a lens that is sitting high on the eye, and of course, that could be an artifact, because the upper eyelid may very well just be pulling that lens up. So when the eye is closed, the lens may center properly. But as you can see in the topography, the lens did indeed decenter while it was being — while the eye was closed overnight. And you can see that the treatment zone is displaced superiorly, and you also have kind of a deep indentation with that blue semi-circle underneath the red, which is where the lens kind of pressed a little too hard and flattened that area. So our steepening and our flattening are displaced, and then there’s even a little steep zone below the blue compression zone, because you can see that the lens is just lifting up off the eye. So this is an example where the fluorescein pattern could have fooled you, but the topography completely verifies that the lens did not position properly, when this patient was asleep. And so the lens will decenter up, and you’ll get this crescent-shaped area of steepening inside the pupil zone. And the apex is decentered superiorly. So this is just another way of looking at the same thing. So you can see in this schematic version that a flat lens will cause excessive force centrally, and the peripheral zone, the alignment zone, is failing to hold onto the cornea, so the lens will slide upward, and the applanation zone or the compression zone, where we want the treatment, is gonna displace superiorly. So in a case like this, we need to raise the lens on the eye. The sagittal height of the lens, as you can see, is insufficient. So when the sagittal height is insufficient, and if we use the nomenclature that we get from the Paragon CRT system, in other words, in this system, the return zone depth is too small, or insufficient, the lens will decenter or ride high. And you’ll get little or no peripheral touch. You can see how the edge is lifting off quite a bit, inferiorly, on that left photo. And then the other component that is adjustable with the CRT system is the LZA, or the landing zone angle. And so the landing zone angle is creating much too much edge lift, and you can see that that needs to be steepened, to bring that back down toward the cornea. This will give too much edge lift, and the lens will land more toward the return zone, or the reverse curve. And you’ll get too much fluorescein pooling at the edge of that lens. So we have to figure out a way to fix that. The easiest way to fix it is to increase the sagittal depth of the lens. Now, that could be accomplished by steepening the alignment curve. Or increasing the return zone depth, depending on which lens you’re working with. If the edge lift is too great, you need to decrease it or tighten the edge lift by pushing the edges down a little bit. It will pop the lens up just a little bit. The tight lid thing — sometimes can be a problem, but sometimes it’s not a problem, because as you’ll see after the patient sleeps, sometimes the lens will center properly, and it only looks like it’s riding high. But if you have very tight lids that’s causing that lens to stay upward, there are a few tricky things that you can do. You can try… Some manufacturers can apply prism. Now, prism doesn’t really help when you’re lying on your back or on your side, but when you’re sitting upright and putting the lenses on, it will help to keep that lens dropped down just a little bit. I will say that this is not done very frequently. Another thing that you could do is increase the thickness of the lens or increase the mass of the lens, literally make the lens a little bit heavier, so it will want to drop downward, rather than ride upward, due to the gravitational force. The OAD, which stands for overall diameter, so in other words, the lens diameter can be increased to assist better centration of the lens. The bigger the lens, sometimes the more room you have in that alignment curve area, to hold the lens in place. And then the other thing that can really give you trouble with centration is if the peripheral cornea is toric. So if you can look at your 0/180, versus your 90/270, and you see a great difference there, then that means your alignment curve is going to fail, to give you 360 degrees of hold, of grab, if you will. You won’t seal off, and fluorescein will start to bleed in under the steep meridian of the cornea, and therefore you may need toric peripheral curves. Now, we’re gonna talk about that in a little bit greater detail later. So I’ll hold that part of the discussion for now. So I want to talk about elevation next. I stressed earlier in the presentation that before you start a case, you really want to inspect and try to understand the cornea that you are dealing with. And what you’re looking at right here are three different views of the same cornea. In fact, it’s the same topography, expressed three different ways. So what you have on the left is called the axial mode. What you have on the far right is the tangential mode. And what you have in the center is the elevation. And briefly, what those mean is: The axial map is describing the power of the cornea. And you can see that there seems to be a significant amount of with-the-rule astigmatism in this eye. You can see on the far right the tangential map describes the shape of the cornea, and we can see that there is indeed some toricity. But the elevation is what I think is the most important map, when it comes to OrthoK treatments. What that elevation map tells you is: How does that cornea differ from a perfect sphere? And what you see is that, at the top and bottom, you have a steeper elevation than you do along the horizontal meridian. And we can also see that this is the fairly symmetrical cornea, so that everything North of the flat meridian looks pretty much the same as South of the flat meridian, and so our anticipation is that, if we were to use a toric alignment curve, we should get pretty decent centration. But before we even design a lens, we look at that elevation to try to understand how well the lens is going to fit on this eye, and so you can see the result, which is an interesting result, down below. We have perfect centration, because when I designed this lens, I knew that I needed to use a toric alignment curve system. And you can even see, if you pay particular attention to the red return zone area, it’s much deeper and darker red at the top and bottom, and a little bit less so along the horizontal, because the cornea was quite a bit steeper in the steep meridian, and flatter in the flat meridian. So the cornea changed more along that vertical steep meridian, and less along the horizontal. So again, we’ll get into a little bit more of that, a little bit later. Now, here’s another example where you’ll see an asymmetrical corneal elevation. Now, this map I think is really intriguing. Because if you look at the axial, and you look at the tangential, yes, we could argue — especially on the tangential — that this is not a perfectly symmetrical cornea. And the apex appears to be slightly decentered. But when you look at the elevation map, you can see that inferiorly, indeed this cornea is significantly steeper, along that inferior vertical meridian, so you would anticipate a lens wanting to fall into that deep, steep zone. Correct? So you’re already thinking in terms of… Well, this lens is most likely going to decenter inferiorly, and as you can see, it actually did decenter inferiorly. Now, this is a situation where with certain lens designs, you can create not just a toric curve in the alignment area, but you can actually… You can even create a quadrant-specific design in the alignment curve, where you might make this lens quite a bit steeper inferiorly, but not throughout the rest of the alignment curve. And that’s getting into some pretty advanced OrthoK. So we won’t really go into too much of that. Suffice to say: Make sure you look at these elevation maps before you start fitting corneas, because that’s gonna give you a really good idea of where the lens is gonna end up. So now we’re gonna go back into the basic troubleshooting. You saw the first fitting anomaly I showed you is when the lens fits superiorly, it rides too high on the eye, which is called a smiley face pattern. This is called a frowny face pattern, because it creates a sad little crescent-shaped decentration. You can see the zone is decentered inferiorly, and the reverse curve topography — the whole thing is shifted down a little bit, as you can see. And that usually almost always occurs for an excessively steep lens, or, in other words, the sagittal height of the lens is too great. It’s not a good match for the cornea. And I’ll show you a few different ways of looking at that. So again, this is that same type of schematic situation, where you can see that the lens is riding too high, and a few things happen when that occurs. The first is you get a very, very small and sometimes absent treatment zone. Because there’s just not enough of that lens applanating the central part of the cornea. You also oftentimes will get air bubbles in the reverse curve area, which you can see there. And the whole lens just looks like it’s dropping down, as you can see in the fluorescein pattern, and then we’ve got too much compression or too much touch in the edges and the peripheral curve system of that lens. So what do you think we need to do here? Well, it’s pretty simple, when you look at it this way, that the angle of that alignment zone needs to flatten. It needs to decrease, which will then lower the roof of that lens, and push it down more onto the cornea. So I’m gonna show you a couple of different looks at that. This, again, is now using the Paragon CRT lens to describe what’s going on here in this fitting anomaly. But you can see in the fluorescein pattern on the top left, the lens sagittal height is so great that there’s actually no defined treatment zone, and you can see to the fluorescein pattern to the right that we appear to be getting a decent treatment zone, but it’s very small, and there’s this big air bubble in that return zone. So that’s another indication that the lens is riding too high. So in that case, the return zone is too great. We need to decrease the return zone depth, to bring that lens a little bit closer to the eye. If the landing zone is too steep, if you get this kind of edge of the lens toeing into the cornea, it’s gonna cause the whole cornea to lift, and so that angle will need to be decreased, to drop that lens down a little bit. So this is what we were just talking about. When the alignment zone is too steep or too tight, we need to flatten it or loosen it. In other words, we need to decrease the return zone depth. If the landing zone of the lens is too steep, if you don’t see enough edge lift, then you know you need to flatten out the peripheral edges a little bit. Now, tight lids can — I told you, tight lids can lift the lens and pull it upward, but they can also push a lens downward. And so sometimes you may need to decrease the edge thickness or the mass of the lens. But if you decrease it too much, you might start getting flexure. In other words, the lens might be too thin to achieve what you need it to achieve. You can also increase the overall diameter to assist in the centration of this fitting anomaly too. And then the same discussion about the toric periphery. If we’re failing to get a good alignment in that alignment zone, then we may need to go into a toric peripheral curve. And in the CRT system, that’s referred to as a dual-axis lens. This is where things get a little tricky, because the superior or inferior decentered lens can occur as I wrote here, when the sagittal depth of the lens doesn’t match the cornea. What I told you before is: If it rides high, it means the sagittal depth is insufficient, and if it rides low, it means that the sagittal depth is too great. But that’s not always 100% the case. Because sometimes if a lens is too steep, if the sagittal height is too great, it still may decenter up or down. It can be variable. So the problem with troubleshooting is knowing which direction you need to go, and fluorescein patterns oftentimes don’t always give you the full story there. You need the fluorescein pattern and the topography information to really understand what’s going on with the lens. The fluorescein pattern, as I showed you in those previous examples, if you don’t see a treatment zone, it generally means that the lens is too steep. If the edges are flaring, a very wide area of edge lift, or if the treatment zone appears very, very, very dark, then you know that the lens is insufficient in sagittal depth, and if you have SPK, central SPK, that also indicates that the lens is too flat. Because the lens should not be rubbing the central cornea. There should always be, even if it’s 3 to 5 microns, there should be a very small volume of fluid between lens and eye. There should never be central SPK. Central SPK — and we’re gonna talk about this a little bit later — means that the lens is too flat or insufficient height, and it’s rubbing the center of that cornea. So we’re gonna ask you another question now. Hopefully everybody’s paying attention. And I’ve been clear in some of my descriptions. So the question is: If a lens decenters inferiorly, if that lens drops, which of the following causes that? Is it insufficient sagittal height? Is it excessive sagittal height? Is the base curve too flat, or is the base curve too steep? And there is one… It may occur… You may think that there is more than one correct answer, but there really is one most correct answer. So we’ll give you guys just a few more moments to vote. Now, I don’t know if you can see the poll results. 63% of you chose the correct answer. Excessive sagittal height. The lens is just too tall, which is causing it to drop down. The base curve — I got 50% of you saying too flat and 20% saying too steep. And I’m glad. Because the base curve should never be considered a parameter for fit. The base curve only controls the amount of myopia that we are correcting. We should not use the base curve at all to affect the fit of our lens. If the lens is dropping, therefore the sagittal height is too high, you might think it’s because the base curve is too steep, but you have to not think about base curve as a fitting characteristic. When we fit gas permeable lenses for daytime wear, we always talk about base curve. Base curve is too steep, you’ve got to flatten it. Base curve is too flat, you’ve got to steepen it. That’s how you adjust the fit. But with OrthoK, the base curve only controls the amount of power, never the fit of the lens. The fit of the lens is done in the alignment area and the reverse curve area and in the peripheral area. So that was great. That was perfect. That was just how I hoped that question would be answered. So this is a tangential map. As I described to you earlier. The tangential map talks to you about the shape of the cornea. You can see that there’s a very oval-looking shape to this cornea. You can see that there’s a with-the-rule pattern to the cornea. Now, as I think hopefully you’ve all come to terms with, I’m a big proponent of looking at the elevation map. So here’s an example of that same cornea with the elevation map. And what I’ve done is I looked, I measured out to 8-millimeter chord. The 8-millimeter chord is where the lens generally fits. That’s where the alignment curve grabs onto the cornea. And so you can see — I measured it, so that we have — you can see that there’s, compared to the reference sphere, I have 28 microns less elevation, superiorly, 40, less inferiorly, and +17 and -5. So you can see here that is not an alignment area. And so generally speaking if, horizontally and vertically, if you differ in your major meridia by more than 25 to 30 microns, then you’re most likely gonna need a toric alignment and reversed curve zone, or a dual axis lens to achieve the proper alignment. This particular map that you’re looking at was done with the Medmont E300, where there is a nice little feature in there, where you can measure out very easily the 8-millimeter chord on the elevation map. The Scout also has a pretty simple way of doing that. And I believe the Oculus — the Pentacam can do that as well. So this is that same cornea that was fit into a lens. And again, you can see where superiorly and inferiorly, in the reverse curve, it’s a lot deeper, darker red than it is horizontally, which again — just further clarifies. And I was asked if I could explain the dual axis lens later, at the end of the conversation, which — I will do that. I will try to do that. The other thing that we deal with when it comes to problem visits is what we call central islands. So this is an example of a central island. What you’re looking at here — the top left map is the prefit, and the bottom left map is the postfit, and then the map to the right is what’s called the subtractive map. That’s where we subtracted the new from the old, and it shows us the difference. The arrow is actually pointing to the zero line. And the contour that you see shows us the… I’m gonna try to use a pointer here, if I can… If I can figure out how to do this. So as we move across this white line, this describes the elevation that we’re seeing. So as we move from left to right, we move from left to right, we come up, we go down, we come up again, we go down. The arrow is right at the zero, and the elevation is right above the zero. So what that’s telling us is that between the post… The prefit map and the postfit map, we’ve actually steepened the cornea centrally. We are a few microns above where we actually started. So we know that this is a central island. We’ve actually caused steepening in that area. And let me go back to my mouse. Central islands are caused when the lens is too steep. When the sagittal height is too great. In other words, the lens is riding up too high on the eye. It’s not pressing down the way we want it to in the treatment zone. So it’s actually causing the treatment zone to elevate or lift. In other words, we’re almost creating a hyperopic effect, as opposed to treating a myopic. We’re steepening the central cornea, instead of flattening it. And that can happen for a few different reasons. First off, just make sure your math is not incorrect. If your topography pattern is — if you took a bad topography, or your K readings are off, perhaps that negatively impacted your design of your lens. Make sure the patient didn’t switch their lenses. One of the first things you do, when you troubleshoot, is make sure they’re not wearing their right lens in the left eye or their left lens in the right eye. And that is pretty easily accomplished by using different colored lenses. We typically put a red lens in the right eye and a yellow lens in the left eye, or a green lens in the right eye and a blue lens in the left eye, so it makes it easy for the patients. You can troubleshoot those lenses in office, if you have a radioscope, and you can make sure those lenses haven’t been switched, if they are indeed the same color. Now, this is not a central island. This is what we call a fake central island. And I will describe that in just a moment. And what you’re seeing here — again, here’s our pre. Here’s our post. Now, you might want to call that an island, but it’s really not. It’s a fake island. Because again, the arrow is pointing to the zero. That part of the cornea is below baseline. So what has happened here is that we’ve created a nice treatment zone way down here, but it’s not a uniform treatment zone. So we’ve brought the treatment zone down, but there’s a little hump in the center of it. This is a fake central island, because this is caused by SPK. So the cornea has been irritated in the center. The topographer doesn’t know how to analyze that, and it creates this steep zone in the center of the cornea. So this is typically caused by a lens that is too flat or insufficient in sagittal height. The refraction should not show more myopia than the prefit. So this is how you differentiate between fake and true central islands. If there’s SPK centrally, it’s most likely a fake central island. If you have indeed decreased myopia, it’s probably a fake island, and if you have increased the myopia, if they started out as a -2 and they come back as a -2.50, then you’ve steepened the cornea, and you know that is a true central island. I hope this is clear. The other thing that can cause a central SPK, besides a lens being insufficient in the sagittal height, or or too flat, is if the lens is really dirty. We can talk about that in just a moment. We’re gonna break for a poll question right now. This is just, again, asking the difference between the true central island and the fake central island. So please give me your answers. We’ll give you about 20 seconds or so to do that. And the results are in. If you said B, you are correct. If you said B and C, you were more correct. So pretty much just about everybody got that right. So excellent job there. Lateral decentration. This is the most difficult one to fix, because there are so many different reasons why lenses might decenter laterally. You can see in that fluorescein pattern that it just looks absolutely beautiful, except for the fact that it’s riding too far toward the nose. You can also see how much cornea is left over temporally. So generally, when it comes to lateral decentration, the big fix for this is lens diameter. The lens should consume about 92% to 97% of the HVID. HVID, for those of you that don’t know, stands for horizontal visible iris diameter. The VVID is the vertical visible iris diameter. Which oftentimes you can’t get. Because the topographer cuts off superiorly and inferiorly. Sometimes you can only do the diagonal visible iris diameter. And you can see on this map right here I have — I’m measuring the HVID, the horizontal visible iris diameter, as you can see right here. So I start my cursor here. I drag it over to here. And it tells me that this is a cornea of 11.83 millimeters. What I did here was I went diagonally, and you can see now that it’s 11.97. So diagonally, we’re always gonna be a little bit larger than we are horizontally. So if you’re designing a lens — let’s say I said it was 92% to 97%, so if you have a 12-millimeter cornea, diagonally about 12 millimeters, 97% of 12 millimeters is about 11.4. So your diameter ideally would be somewhere around 11.4, on a 12-millimeter cornea. Let me just get rid of the highlighter here. Okay. And once again, when it comes to lateral decentration, it could also be caused by the insufficient sagittal height, not just the diameter. So again, if you’re seeing SPK, the lens is probably too flat, which is causing it to decenter. If it’s too excessive, then it may drop or decenter laterally. The Asian eyelid is a real challenge. It fits very tight, it grabs the lens, and it really pulls the lenses up or sideways, or it pushes them down, and you’re gonna see in some videos I have a little bit later how to try to understand that. There was a question that just came up about sleeping position, which is appropriate. And the question was: Can an unusual sleeping position cause fitting problems? If so, what are the common problems? And absolutely, if you have people that are face sleepers, and they smash their faces into the pillow, that’s gonna cause a little bit extra additional downward pressure of that lens. Sometimes you really do have to counsel your patients about their sleep patterns. And encourage them to either be on their back or on their sides. Sometimes there’s nothing you can do about the way people sleep. But if your lenses fit well, and you have good alignment, generally the sleeping patterns won’t cause too much difficulty in your results. Lagophthalmos is something to watch out for. If you have patients that do not keep their eyes closed when they’re asleep, they’re gonna start drying out quite a bit. Sometimes if you have a lens that you can’t get to center, no matter what you do, the advanced fitters will go into corneal scleral designs, where they might go to a very large diameter lens, like a 13.5 or a 14.0, but this is very advanced stuff, and it’s above what I want to talk about today. Make sure your lenses stay clean. Have your patients bring them into the office every time they come in for a follow-up visit, so you can inspect them. They might clean them while at home, but they might be a heavy depositor, and you get a lot of deposits building up on the lens. Progent is a great product to remove any residual protein. This should be an easy one. What is ideal lens diameter for a 12-millimeter cornea? You’re all gonna get this one right. Okay. Just about everybody got that right. 92% to 97% of the HVID is correct. A couple proposed 0.2 millimeters smaller than HVID, which is a good answer also. There’s no right or wrong for this. A lot of this has to do with personal preferences, but I have found that going about 95% is the way to go. Question: Is this lens decentering? It sure looks like it, doesn’t it? But when we really analyze this, in a little bit greater detail, we find that it’s not quite as decentered as we think that it might be. And you can see here, because the window of cornea gets cut off, so we created — that the circle is the extent of the cornea, where it gets cut off, and when I measure edge of cornea to edge of treatment zone, we can see that there’s only a difference of about half a millimeter. So even though it looks profoundly decentered, this is a situation where patient has a large Kappa angle, and so the entire topography is displaced one way, and so this is another example where the retinoscope showed that the treatment zone was actually pretty well centered within the cornea. This was a patient of mine that came in for their one-day postop, and that was what the cornea looked like. That was what the topography looked like. And that was what the lens looked like on the eye. It’s maybe slightly nasal, but you can see it’s actually pretty well centered over that pupil. What happened was: This was a patient that came into my office, wearing the lens. And the lens had become bound. It wasn’t moving at all. It was almost stuck to the eye. And there are some practitioners that like their patients to come in after the first night of wearing their lenses, with the lenses still in their eye. I don’t, because of this. Lens binding, if your lenses fit a little bit too tight sometimes, can cause a lens to bind. It’s important to just make sure patients know how to remove a lens that is stuck. If they’re having any trouble getting the lens off, you want to put some artificial tears in, you want to look up and gently depress the sclera, just below the edge of the lens, to create a little air pocket, to slide up under the lens, and then that will help that lens come right off the eye. There was a question about central staining earlier. How do we evaluate central staining? And when do you let the patients keep wearing their lenses, or when do you make them stop? If you have very mild staining, grade I or less, that may be from how the lens was taken off the eye. They might have been a little rough. Maybe there’s slight drying. If you have grade 2+, it’s unacceptable. And if you have a fake central island, or you have really deep staining centrally, there’s generally a problem with your fit. This is just an example of dense corneal staining. And when you see something like that, that may be a sensitivity to the cleaning products that you have your patient using. Where it’s so diffuse like that. It may be a reaction to the preservative. Wettability of your lenses can be a problem. Sometimes that can happen when there’s a lot of defects or surface defects. And an older lens can sometimes warp. One of the ways that you can tell is if you do a topography over the lens on the eye, you might be able to see a lot of toricity or warpage. Corneal abrasions do happen. That can happen from rubbing the lenses. It can happen from being not that good at putting in and taking out. Make sure your patients are really well trained. And if they have dirty lenses, chipped lenses, all those things can lead to abrasions. You have to be really careful with abrasions, that you get those healed up right away. Make sure your patients know to call you if they have any questions, and not just to go to their primary care physician or another doctor that doesn’t know how to deal with OrthoK lenses. This is something called dimple veiling that you might see. If the lens is very, very steep on the eye, an air bubble might break up into several mini-small air bubbles. And these cause little dents on the eye. They usually resolve within 1 to 2 hours. But typically when this happens, either the lens is too steep, or they have not filled the lens with a proper solution. We generally use sterile saline or non-preserved artificial tears to fill a lens before they put that lens on the eye, to prevent air bubbles. You’re gonna often see an iron ring in what would be the area of the reverse curve. As you can see there, it’s really inconsequential. Microbial keratitis. We don’t want to see corneal ulcers go bad in our patients that wear any contact lenses. This is really important. Your patients have to know, if their eyes are red, if their eyes hurt, if they have light sensitivity, they have to get their butts to your office, ASAP. There was a really great study done to test the safety of OrthoK. It was a retrospective study. It showed that this was done by Ohio State University. Mark Bullimore ran this study, and it showed that over 10,000 years of wear, there were 7.7 cases of microbial keratitis. So we know that it’s a safe modality, but your patients need to be well trained, and understand what to look for, if troubles happen. And then one other thing that can happen is patients might lose effect. So you might have a great treatment, and suddenly it’s not great anymore. Again, like I said before, look for warpage. Look for dirty lenses. Make sure they have them in the right eyes. And siblings in question mark — I have seen situations where I have two brothers wearing OrthoK lenses, and brother A started wearing brother B’s lenses by mistake. So always… Just remember, if your patients can do it, they will do it. And then the last thing I wanted to talk about is glare and light sensitivity. We do see that from time to time. We want to make sure our patients know ahead of time that glare is real. It happens. It generally gets much better with time. Sometimes we have to increase the optic zone of our lenses. The treatment zone area. Sometimes there are doctors that are using Alphagan or now Lumify. I don’t know if you have those in your countries. But these are medications that can be used off-label to cause pupil miosis, which can be helpful at night. This is a Wave lens, and I’m showing you the design window here, because I think it illustrates how the lenses should be fit on the eye pretty well. So you can see that the treatment zone is down in this area. This is a tear layer profile. So where the lens is flat, where it’s flat, you see it’s very flat. Where the lens is steep, the tear layer profile comes way up high. That’s why we see so much fluorescein there. And this is the alignment area. So when we talk about dual axis lenses or we talk about toric lenses, this alignment zone here is gonna be flatter along this meridian, and when we change this to the vertical, it’s gonna be a lot steeper. So we’re gonna have two different curvatures. We’re gonna have a flatter curve here horizontally, and a steeper curve here vertically. And I apologize if this isn’t super clear on how to see that. So here’s a question for you. We’re not gonna do it as a poll. But: Is this a good fit? Or is it a bad fit? It kind of looks like it’s not very good. It’s riding superiorly. And nasally. But my topography on this was really quite well centered. So why is that? Well, if you watch this video, you’re gonna see that that lens indeed is decentered. However, when I pull the lids away from that eye, look at how well that lens centers. So the theory behind that is: The lid is what’s causing the lens to push toward the nose. But when the lids are closed, when the lids are not grabbing that lens, it’s gonna center well. So we know that the reverse curve and the alignment curve and the peripheral curve have been well designed on this lens. Here’s another one that you see looks like it’s riding very low. What do you notice? The treatment zone looks thin. It doesn’t look very dark. There’s an air bubble in the reverse curve. So we’re thinking… This is an excessively steep lens. Correct? You see we didn’t get a very good topography. And this is another. Look at that wave profile view. So what we did here… Let me just grab the highlighter. So you can see that the alignment zone of that lens was lifting up off the eye, so we flattened out that alignment zone. We brought the edge lift up a little bit, to create a more flat alignment. In which case the sagittal height of the lens dropped. And then that — making that modification to the alignment zone created that — gave me a better fit on that lens. This is one that also looks a little bit steep, as we’re getting a bubble, and we’re seeing a very small treatment zone in the center. And that’s how it turned out. A little bit low, and maybe a small treatment zone. So what we did here was… We went from this smaller treatment zone to a wider treatment zone. And we did that by decreasing the height of the reverse curve here. And flattening the alignment curve here. And so what we turned out with was this lens. And we can see. Yeah, there are a few bubbles in the reverse curve. And it’s still a little bit light in the center. But we were able to get a much wider treatment zone. Now, the whole lens is maybe slightly inferior still. And you can see on these difference displays how much larger the treatment zone became, just by lowering the sagittal height of that lens a little bit. So just a few pearls, and then we’ll save time for some questions. When you start doing OrthoK, you get very excited about doing OrthoK, and every patient that walks through your office you want to do OrthoK for, but just because they want to doesn’t mean that you should. Make sure that it’s a good candidate. You want a symmetrical cornea. When you’re just getting started, you probably want to stay below about a -4.00. And you want to have a well motivated patient. You want to talk to them a lot. You want to teach them a lot. You want to give them information that they can take home, that’s written, as to how to care for the lenses, how to put lenses in, how to take lenses out. I highly recommend doing your own topography, because they need to be just right. Especially for the prefit maps. So be careful when you delegate too much to staff. And try to really spend time with these patients, especially in the beginning. They’re gonna have a lot of questions. Don’t make changes too quickly. I think that’s the biggest mistake that new fitters make. Give the process time to work. Make sure that you take topographies at every visit. Make sure you charge enough for your time and expertise. And try to learn as much as you can. Continuing education is a variable with this, and it’s good to do it this way, but it’s even better to do it in person, where you can have one to one interactions, and people take out their laptops all the time, and pull out topographies, and talk about photos and patterns and designs. And then just a quick little… I’d like to just throw one thing out at you. As I told you, I run the American Academy of Orthokeratology. The International Academy has chapters around the world, as you can see here. And so I would encourage you to consider joining one of your local chapters. That run educational meetings — and it’s a terrific organization. So at this point, I’ll open up the floor to questions. There is one here. Some lens designs state that they can correct much greater myopia and astigmatism than others. Are there any disadvantages to using these lenses for all patients? No, absolutely not. So there’s basically — there are custom designed lenses, and then there are more empirical fit lenses. The custom designed lenses, like Wave, like EyeSpace, like OrthoTools, like RGP designer — you can do just about anything with those lenses that you want to. And there’s really no disadvantage. You can use those for every single patient. It’s not overkill to do that. You don’t have to overengineer a lens. But you have the opportunity to dig deeper into the engineering of the lens, if you’re needing to troubleshoot a poor fit. So some of the empirical lenses out there — Euclid makes a terrific lens, and Paragon CRT makes a terrific lens. Those lenses don’t have as much customization, but they do work very well. So most doctors that do OrthoK use multiple different lenses for multiple different situations. So I do hope that answers that question. Okay. We don’t have any open questions right now. But we can stay for a few more minutes, if anybody has anything else they’d like to ask.

>> Thank you, Dr. Levine. Yeah, we’ll wait a couple more seconds and see if any more questions come through.

DR LEVINE: Yeah, no problem. All right, Lawrence. I guess we should wrap it up.

>> Yep, I think that’s good. Thank you so much.

DR LEVINE: Yep, thank you very much, everybody, for attending. I hope this was educational for you all.

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December 3, 2018

Last Updated: October 31, 2022

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