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.
During this live webinar, Dr. Wantanbe discusses how Orthokeratology lenses mold the corneal shape at night, the risks and benefits of this technology, and the basic principles of fitting Orthokeratology lenses on your patients.
Lecturer: Dr. Ronald Watanabe, OD, FAAO
DR WATANABE: Hello, everyone! My name is Ron Watanabe. I’m an associate professor at the New England College of Optometry. I’m gonna talk to you today for the next hour or so about orthokeratology. So orthokeratology is the programmed alteration of the corneal topography to create a predictable change in refractive error to improve uncorrected visual acuity. Typically, we’re correcting myopia, but there are other types of refractive errors that we can also correct by changing the shape of the cornea. And typically, we are using reverse geometry, rigid gas permeable contact lenses to reshape the corneal surface. These days it’s usually done as an overnight procedure with no lens wear during waking hours. Which is a little bit different than how it started out. Ortho-K has been around for a couple of decades. It started out with regular PMMA lenses, then into gas permeable lenses, and in the late ’80s, early ’90s, with the advent of reverse geometry types of lenses, we were able to do more controlled and predictable types of changes with the contacts. So today it’s a fairly good procedure. Very predictable. And as an overnight procedure, it’s become more popular as a corrective option for patients. So my first poll question is: What is orthokeratology indicated for the correction of? Is it myopia, hyperopia, presbyopia, or all of the above? Okay. So most people said that it’s indicated for the correction of myopia. A few people said hyperopia. And a lot of people also said all of the above. And the answer depends on what your definition of indication is. Orthokeratology is an FDA-approved procedure in the United States. In the United States, it’s only approved for the correction of myopia, up to 6 diopters of myopia, for the Paragon design, and up to 5 diopters of myopia for the Bausch and Lomb designs. And it’s also approved for the correction of astigmatism, up to 175 for the Paragon design and up to 1.5 diopters for the Bausch and Lomb designs. There are designs that are in existence that can also correct hyperopia, presbyopia, so it can be used for those things, and I have used orthokeratology lenses for those types of patients as well. But if you’re talking about the strict definition of FDA approval, it is really just myopia and astigmatism, up to a certain amount. These days, the primary indication also is in children who have progressive myopia. Children who are becoming more myopic by a diopter or more a year, and whose parents are concerned that they’re gonna end up being very myopic when they’re an adult. And as we know, high degrees of myopia are also associated with ocular changes that may result in other problems down the road, such as retinal detachment and other retinal problems, macular degeneration, and glaucoma. So for a lot of parents, myopia control is a good option for their kids. And so these days most of my patients who are coming in for ortho-K treatment are actually children who are becoming more and more myopic. I notice there are a number of questions about the use of ortho-K in children. In the US, there is no age restriction or age limitation for ortho-K. The youngest child that I have fit with ortho-K is 6 years old. I’ve heard of other doctors fitting children as young as 4 years old. The main concern with fitting children that young is, first of all, will they be accepting of the lenses on their eyes? Are the parents going to be able to put the lenses on and take them off and take care of them properly for their children? And are the children going to be able to communicate any problems that they might be having with the procedure itself? In my practice, I will fit children — you know, usually starting at around age 8. But it really depends on the child and the parent-child dynamic. If the child does not seem to be willing to accept the procedure and wearing the lenses overnight, then I will not proceed with it, even if the parent wants to. It really has to be something that the child is going into, knowing what the procedure is about, and what their experience will be. So I fit children, like I said, as young as 6. I usually start around age 8. Sometimes I will put it off if the child doesn’t seem ready or really does not want to proceed with the procedure. The vast majority of ortho-K is performed for myopia. Even in adults. And recently, like I said, children are the primary population being fitted for ortho-K, due to its apparent myopia control effects. In terms of efficacy for myopia correction, it’s very effective, as long as you stay within the bounds of what ortho-K can do. Like I said, with the FDA, it’s approved for up to -6 diopters of myopia and 1.75 astigmatism. The efficacy does decrease as the myopic refractive error increases. So really, once you get above -4 or -5 diopters, the results are not as predictable. You’re not going to be able to correct them quite as well. Although I have had patients up to -8 diopters who I’ve been able to correct to 20/20. It really depends more on the patient’s cornea and how much change the cornea can go through, and that’s not something that you can necessarily predict before you start treatment. So I would say up to -4. Fairly easy to say that it will be fairly effective. Between 4 and 6 diopters, I’m pretty sure I can correct them to at least 20/25. But beyond -6, it becomes much less predictable. You can use it for people who have more than 6 diopters of myopia, but that would be considered an off-label use of the lenses and the procedure. In the US, even if something is not FDA approved for a certain purpose, the doctor can use the lenses for that purpose, if they feel that, in their clinical judgment, it would be of benefit to the patient. And that’s why I’ve been able to correct patients who are above -6, as long as they understand that for them it is an off-label use. There are claims by some manufacturers that their lenses can correct up to 10 diopters of myopia. I have not done anything that high. In terms of other efficacy points, it does induce aberrations of the eye. Primarily it will induce spherical aberration, and that’s one thing that actually helps, in terms of myopia control, which I’ll talk a little bit about today. And if the treatment is offcenter, then you can also induce other aberrations, such as coma, and other off-axis types of aberrations. In terms of myopia progression, there’s a lot of study being done in this area right now. If you look at most of the published studies, they’ll say that on average it will reduce myopia progression by about 50% or so. The latest review says that you have an increase in axial length — decrease in — less increase in axial length — by about 45% overall. That was just published last year. Here’s a list of some studies over the years that have looked at the effects of ortho-K for myopia control. As you know, ortho-K is just one of several procedures that are being used for myopia control currently. And if you look at all the studies, they measured either differences in axial length, increase over time, or refractive error increase over time. And again, most of them find that you have about roughly 50% decrease in axial length progression or refractive error progression over time. And this doesn’t mean, obviously, that your patient will stop changing. That’s what we would like to see. And that’s what we do see in some patients. But we do have to understand that it’s not going to stop myopia progression 100% in all of your patients. And that’s something that you have to discuss with the parents of the children. And for the most part, they are okay with that, because it is better than conventional correction, where they would still progress at a rapid rate. And even though you’re only offering that it will slow progression by 50%, most parents are excited about that amount of decrease. And currently the theory behind myopia control is this concept of the image shell. Emmetropes have a type of image shell where, if the center of the retina is — or the center of the image is in focus on the retina, in the periphery of the eye, the image is actually focused on or in front of the retina. And for emmetropes, that keeps their eyes emmetropic. For myopes, the image shell is in front of the retina, across the entire retina, including the fovea, and when we try to correct those patients with traditional correction, such as glasses or contact lenses, most of the — in some patients, those corrections will create an image shell such that the fovea might be in focus on the retina, but the peripheral image is actually focused behind the retina. And for whatever reason, that seems to stimulate the eye to grow, so that the peripheral retina can meet the image shell behind the eye, and that causes the foveal image to defocus and be in front of the retina now, and therefore the patient has become more myopic. And if you then correct them with stronger lenses, you create an image shell similar to this again, and their eye continues to elongate. With ortho-K and also with soft center distance bifocal contact lenses, we are able to — at least theoretically able to — create an image shell similar to that in emmetropia, where the center of the image may be focused on the fovea, but the peripheral image is either on or in front of the retina. And that theoretically will slow or decrease the stimulus for the eye to grow, and therefore decrease myopia progression. That’s the theory that we are going by now, and ortho-K seems to be able to do that. And here’s just a study that was published that shows the power of the lens or the refraction through the different areas of the pupil, based on ortho-K lenses and soft bifocal lenses, with a center distance correction. And this presumably will translate into creating the type of image shell where the peripheral image is in front of the retina, and thereby slowing progression of the myopia. So that’s what I’m gonna talk about, in terms of myopia control. There was one of these lectures, an Orbis lecture, on myopia, that was presented by Dr. Vera Diaz. She talked quite a bit about myopia control, myopia progression, and the theories behind that. So if you want to learn more about myopia control and the various treatments available, you can review her lecture about that. So back to ortho-K. When we fit patients with ortho-K lenses, what we are trying to do is to create change in the cornea, in a controlled way. And based on what we know about myopia control, ideally what we want to do is to flatten the central cornea and steepen the midperipheral cornea, so that you create a less myopic central zone, with flatter curvature here, but a more myopic midperipheral zone that will cause the image in the peripheral retina to focus in front of the retina. We do that by using lenses that are shaped in this way. This is a reverse geometry design, where the central curve is actually flatter than the secondary curve or the midperipheral curve here. So by fitting a lens that’s very flat centrally, we create forces that will push on the cornea centrally, and by fitting a lens that has a steeper midperipheral zone, we create a negative force there that will actually cause the cornea to steepen in the midperiphery. So the result is an altered corneal shape that’s flatter in the center, steeper in the midperiphery, and that reduces myopia centrally. When we put this kind of lens on the eye, we really don’t want to create a true mechanical contact between the lens and the cornea. Ideally, what we want is a really thin layer of tears there that the lens is pushing on, and that hydraulic force of pushing the tears into the cornea is actually what causes the cornea to change. So if the lens is actually touching the cornea, which I’ll talk about a little bit later, we find that we can create some mechanical problems there. So we want to maintain a thin tear layer there that the lens pushes on. The tear layer then pushes on the cornea. And then in the midperiphery, the thick tear layer there causes a negative pull force that allows the cornea to be steepened and come out to meet where the contact lens is. So we’re doing some hydraulic changes to the cornea. And if we’re able to maintain a little space there, we’ll have less problems over time. This was a histological study that was done by Jennifer Chu out at Pacific University. She actually put some ortho-K lenses on cats and had them sleep with the lenses, and she looked at the changes in the corneal epithelium and stroma at short-term time lengths and actually longer time lengths. And what she found was that when they put on myopic ortho-K lenses, meaning flattening the center of the cornea and steepening the midperiphery, at four hours you had no changes in the stroma, but in the epithelial layer, you actually had compression of the epithelial cells. You still had the same cells there, but the contents of those cells were squeezed and pushed into adjacent cells, such that the central cornea became flatter — or thinner, I should say — and the midperipheral epithelium became thicker. And once you put hyperopic correcting lenses on the eye that were steeper in the middle, than the midperiphery, she found that the cells in the center of the cornea became larger or swelled up, and those in the midperiphery shrank down. They were squeezed. So short-term, we see that we do have significant changes in the thickness of the epithelium, and so even after one night of wear, you’ll have a significant change in the corneal topography and a significant change in the patient’s vision, and we see that on all of our patients. At 14 days, we see further changes. Not only did we see a thinning of the epithelium centrally, on those myopic ortho-K lenses, but we also see that we have fewer cell layers. The cell layers have migrated from the center out, more towards the midperiphery. And in the midperiphery, we see more cell layers. So these are longer term changes. They take longer to happen. And this is probably what allows us to have more stability over time, as the patients do the procedure longer and longer. So we have compression of epithelial cells, in addition to migration of epithelial cells over time. And in the hyperopic correction, we see similar things, except that we have compression and migration of cells from the midperiphery and an increase in cell layers and increase in cell size in the center. And that causes central steepening of the cornea. Clinically, we won’t see those things, because we do not do histological sections through patients’ corneas. But what we do see are changes in corneal topography. If you’re going to do orthokeratology on your patients, you should definitely have a corneal topographer to monitor what you’re actually doing on the cornea. Without corneal topography, you really don’t know what kind of changes you’re making on the cornea, and you really won’t know how to improve those changes, if the patient’s having problems with their vision. Again, most of our patients are gonna be myopes. And what we see with myopic ortho-K is that we have a flattening of the central cornea. And then we have this midperipheral ring of steepening. Where you see the red zone. And then beyond that, you’ll have a flat peripheral cornea, like you do in a normal cornea. And depending on how much you’ve flattened the central cornea and steepened this midperipheral cornea, you’ll have a certain amount of myopic correction. Like I said, you can use this for hyperopia and presbyopia as well. It’s definitely not as commonly done, but it can be done. We don’t do this on children, typically, because hyperopic children are not going to become myopic, typically, unless it’s an unusual case. And hyperopic children generally don’t have too many visual complaints, unless they’re very hyperopic. So this is primarily gonna be done in adults. Especially adults that are pushing presbyopia. But with hyperopia, we see that we have a central steepening of the corneal topography. And in presbyopia, which is uncommon, but can also be done, what we try to do is have a small central zone that is steeper, that gives the patient the add, and around that you have the flatter zone, which is going to be their distance correction, and sometimes you have a ring of steepening around that as well. So this gives you more of a topography that’s similar to the kind of refractive profile you’ll get with aspheric multifocal contact lenses, where you may have a center near zone and a peripheral distance zone. Obviously the optics of this kind of correction are not gonna be as good as single vision correction. I mean, you already have some aberrations, even with single vision correction. So it really takes a motivated patient to want to undergo this type of treatment. But for the right patient, it can work quite well. The patient can see both distance and near, without the use of reading glasses. All right. So the next poll question: Which of the following structural changes does not happen with ortho-K treatment? Reduction in epithelial cell layer centrally, meibomian gland distortion, reduction in sub-basal nerve plexus density, or reduction in endothelial cell density? All right. So that’s good. Reduction in endothelial cell density. I think that’s an important thing, because what we don’t want to do is compromise the cornea in any way, especially when doing this treatment with children. The other things do happen. This is what I just talked about, in terms of cell layers. Epithelial cell layers. There is the possibility of distorting meibomian glands, and that can cause problems with tear film and dry eye down the road. And possibly even complications wearing the lenses, because of tear film compromise. This one is a recent finding. At least short term. That can be of concern. Are we affecting corneal sensitivity? And because of that, are we going to affect corneal healing response? And lack of ability to sense corneal problems over time? That’s something that we’ll have to see over time. But at least we’ve seen that there really is not a reduction in endothelial cell density. So we shouldn’t have any issues with corneal edema or other corneal — long-term corneal issues over time, based on endothelial problems. Several studies have looked at the safety of ortho-K. I’ll just go through a few of these findings. Obviously we do see epithelial changes. That’s what we want to achieve. In terms of cell thickness, and number of cells in the epithelium. In terms of the stroma, we typically don’t see stromal thickness changes centrally. But we do see a little bit of thickening midperipherally. That doesn’t seem to be associated with clarity problems with the cornea, but in some patients, if you have extreme changes in stromal thickness, you might have some changes in corneal clarity. And then again, nerve plexus density — we’ll have to see if that becomes a significant issue. So far in the amount of time that I’ve been doing ortho-K, which is over 15 years, I haven’t seen any significant problems. Or at least clinical problems associated with this finding. In terms of conjunctiva, we sometimes see papillary hypertrophy. Like you do with any contact lens wear. This is going to happen more with lenses that are irritating the tarsal conjunctiva, with poor edge design or high edge lift designs. Typically with ortho-K designs, we don’t see a lot of high edge lift designs. We’re typically low edge lift. So that’s usually not an issue. If the patient is not taking care of the lenses properly or they tend to have a lot of protein deposition, we might see more of that. So that’s something we have to keep an eye on and maybe manage with better cleaning regimens or more frequent lens replacement. In terms of tear film, we do see some changes in tear film quality, and that may cause some problems for patients over time. And in the choroid, presumably due to issues related to myopia control, we see some changes in the subfoveal choroid. I have a couple questions that have come up: How often is it recommended to put anesthetic drops? I know some patients put them in every day, during two to three years. How dangerous is it? I never recommend anesthetic drops. Even when I’m in the office, putting lenses on patients. Because long-term, if you have patients using aesthetic drops, they can cause softening of the epithelium and even melting of the corneal epithelium, so you should never give anesthetic drops to patients to take home. If they really are uncomfortable in the office, I may put a drop in the first time we put lenses on, but I tell them this is not something they can do long-term. In the office, I put them in solely to be able to evaluate the lenses on the eyes, but never to help them adapt. If they just cannot adapt without anesthetic drops, then we discontinue the procedure. And yes, you can definitely have my PowerPoint file. I will send that off to Lawrence, and he can make that available to you. Okay. The most serious complication we see with ortho-K is ocular infection. And there have been a number of studies that have published statistics on corneal infections. The first one came out in 2007. By Watt and Swarbrick, in Australia. And they found that at that time there were quite a few cases of microbial keratitis, and alarmingly, most of those were either pseudomonas or acanthamoeba. But what they found was that most of those cases happened in Asia, where the fitting and follow-up of ortho-K was unregulated at the time. And people were using tap water, and not really cleaning lenses properly, using proper solutions. They were not being followed up properly. And because of that, a lot of infections resulted. After that, ortho-K became more regulated, and we saw a significant drop in cases of microbial keratitis after that time. More recent studies have shown that pseudomonas — ortho-K lenses do retain more pseudomonas than alignment fitting gas permeable lenses, just because of the nature of the tear layer under the lens, so you have to make sure patients clean and disinfect lenses properly and are using solutions properly, proper hygiene. A couple of other studies found that there may be an increase in infection rate, compared to regular contact lens wear, but it’s really impossible to determine the risk of complications, because of non-standard reporting and the lack of randomized clinical trials, but that’s something that’s probably going to be looked at more so down the road. Mark Bullimore found that overall, in his studies and his surveys, that the risk of microbial keratitis is very similar to that of other overnight contact lens modalities. So if your patient’s parents are concerned about infection, yes, there is an increase in risk of ocular infection, compared to no lens wear. And probably a little increase in risk compared to daily lens wear. But compared to other overnight modalities, it’s very similar. Okay. Is there a difference in myopic control in axial myopia and refractive myopia? That’s a good question. And honestly, I don’t know the answer to that. I think primarily with myopia control, we’re talking about axial myopia. Because we’re talking about axial — increases in axial length. And it’s found that ortho-K does decrease increases in axial length over time. And another question is: Is there a lower limit of power to undergo ortho-K? And there really is not a lower limit. However, if you’re concerned about — or trying to do myopia control with ortho-K lenses, if you are correcting a very low refractive error, like a -1 or somewhere in that range, you’re not gonna create as much of that steep myopic ring in the midperiphery. And that’s what creates the myopia control effect. So you’re probably not gonna have as good a myopia control effect, because of that. So in my patients that have low refractive errors like that, where the patient is concerned about myopia control and want to get them into lenses early, I tend to recommend soft bifocal lenses, because I know I can create more myopia control effect, even in those low myopes. If parents want to continue with ortho-K despite that recommendation, I will still fit them, but they have to understand that there’s less myopia control effect, so they may still progress, more so than patients who are higher myopes. Okay, so bottom line in terms of safety: Compared to other contact lens modalities, you may see certain changes, but overall, it’s relatively safe. And as long as the patients and parents understand the increased risk of microbial keratitis, compared to non-lens wear and daily lens wear, most parents are fine to go ahead with it. What I do is I educate the patients and the parents extensively before we start, to make sure that they understand that cleaning, disinfection, hygiene, and lens replacement and follow-up are essential for successful ortho-K wear. And in my patients, the only patients who have really developed significant problems are those who have not adhered to those. Patients who have either not taken care of their lenses properly or patients who have not come in for their follow-ups and not replaced their lenses on a regular basis. I recommend ahead of time that they replace their lenses about once a year. In some cases, they can go longer than that, if they just don’t produce a lot of protein, they don’t have a lot of deposition, they really take good care of their lenses, and their lenses look good on their follow-up visits. But otherwise, I definitely recommend replacing lenses once a year. All of this, in terms of safety and the proper fitting of ortho-K, I think is critical, to make sure that we are taking the best care of our patients that we can. And in the US, at least, and I think in all countries now, the companies that make and design and sell ortho-K lenses require certification to make sure that the practitioners know how to fit the lenses and know what the risks are and how to manage those risks in their patients. So this is just an example of a certification test. I’m certified in four or five different designs now. I don’t remember how many. It’s very simple to do, but it is something that is important to do, to make sure that you’re taking care of your patients properly. All right, so let’s get into the actual fitting of ortho-K lenses. There are a number of things that we have to do, to first of all determine if they are a good candidate, and then how do we design the lenses and then follow up patients and make changes when the patients aren’t responding appropriately? So again, the indications — we already talked about this. Myopia up to -6 is FDA approved. I’ll tell patients up to -4 that it should not be an issue at all. They should be able to enjoy good vision throughout the day. Beyond -4 and up to -6, I tell them: Most likely we’ll get good correction, but we may not get to 20/20. Beyond -6, it’s an off-label use. So I definitely advise patients that they may not have good correction, and it may not work for them. Who are good candidates? Motivation and appropriate expectations are definitely important. Motivated, because, for the majority of patients, they will have to wear these lenses every night to maintain good vision and to maintain myopia control effects. If they are not motivated to wear them every night, it’s not gonna work. I have a patient right now who — she’s 11 or 12 years old. She doesn’t wear them every night. She wears them for a week at a time and stops wearing them for a week. Despite what her mother tells her. And she’s progressing in her myopia. And her mother is very frustrated with her, and I can understand why. And, you know, with children, it’s hard to gauge motivation ahead of time. You really have to go by parents and the parents’ willingness to stay on top of the children, to make sure they’re doing this properly. But if you have a child who’s doing this on their own, and they’re really not motivated to do this, it’s probably not gonna be an effective procedure. So you really have to try and assess that, before you start fitting them. And then appropriate expectations. It’s not gonna make their vision perfect. It’s not going to permanently change their vision. And it’s not going to 100% control their myopia, in most cases. So they have to know those things before you fit them, or they will be disappointed, and they will be upset with you that it didn’t deliver as they expected. Make sure the refractive error is within what the lens can do. Progressive myopes are really good candidates, because they are used to having their vision blurry and getting worse and worse all the time. Chances are you’ll make things better for them, both in terms of their day-to-day vision and also in terms of their progression over time. You also want to make sure they have good ocular health to begin with. You don’t want to see patients with a lot of staining, blepharitis issues, tear film issues. Those kinds of things. You don’t want to fit patients who have keratoconus or other corneal irregularities, because those are compromised corneas already, and you’re doing a procedure that might compromise it further. So you want to make sure that they are normal and have good ocular surface health. You can fit this on anyone who wants to be free of spectacles. Maybe patients who considered refractive surgery but really did not want to go through with surgery. Athletes — it’s great for athletes, especially swimmers or people who are in the water all the time. Because we know that being in the water with soft lenses especially increases the risk of eye infections. Questions about whether dry eye patients are good candidates… I would say patients who are borderline dry eye, having comfort problems with soft lenses, are good candidates. Patients who are comfortable without their lenses on but now with contact lenses are having comfort issues, they will probably do fine with ortho-K. And in terms of soft contact lens failures, I guess depending on why they failed with soft contact lenses. Some patients may do fine with ortho-K treatment, where with soft lenses they just did not do well. More questions. Is once a year replacement compulsory? No, it is not. It’s really your judgment call. I recommend it, because for most patients, that’s about the time when the lenses look like they need to be replaced. And I want to make sure that they don’t have problems over time. Does a patient’s acuity vision change during the day? It can, especially when you’re trying to correct high levels of myopia with this treatment. The corneas do regress a little bit during the day. But that becomes less and less, the longer they do the procedure. Like I mentioned earlier, you know, the early changes are really cell compression, and that rebounds fairly quickly during the day. But cell migration does not. So if you have a movement of cells from the center to the periphery, that takes much longer for vision to change, and I actually have some patients who can go two days without having to wear their lenses, and they do just fine. When should we stop ortho-K treatment? Excellent question. I don’t have a good answer for that. What I’ve been telling parents of children is that typically, if patients stop becoming more myopic in their late teens or early 20s, it’s impossible to predict when a child will stop changing. So I tell parents that typically, when they go away to college, around age 18 or so, that’s when we can think about stopping treatment. But even then, some people will still progress through their 20s. So at that point, it’s probably more a lifestyle decision. When they’re in college, are they sleeping long enough to continue to wear the lenses, so that they’re effective? Some yes, some no. But minimum, I would say, 18 years old is when they can stop, if their concern is myopia control. Otherwise they can continue on indefinitely. I haven’t seen any patients who have had problems just because they wore the lenses for X numbers of years. I myself have been wearing ortho-K lenses for almost 20 years, and I so far don’t seem to be having any problems. But we don’t know long-term — 20, 30 years, if the patients wear lenses for that long, if they will start having chronic problems, because of ortho-K treatment. All right. How to choose a type or size of ortho-K? I’m gonna get into that right now. Have you seen a rebound increase in stopping ortho-K lenses? Again, I think that depends on the patient and when you stop treatment. If this patient were to continue to progress to age 25, but you stop at age 18, yes, they’re gonna continue to increase. But if they would have stopped at age 18 and that’s when you stopped, then you probably will not see an increase. For the patients that I’ve had who have stopped treatment at around age 18 or age 20 or age 22, I actually have not seen an increase beyond that. But that’s not necessarily because of ortho-K treatment. I think that’s just because those patients would have stopped changing at that point anyway. All right. And who are not good candidates? The higher refractive errors, astigmatism that’s greater than their myopia. We tend to be able to correct only about half of the patient’s astigmatism with most of these treatments. So if they have a lot of astigmatism and very little myopia, it tends not to work quite as well. Hyperopic astigmats, it doesn’t work well for those patients. Against the rule astigmats. That doesn’t work as well. It doesn’t correct any internal astigmatism. Patients, especially adults, with large pupils will complain a lot about nighttime glare. So that can be an issue. And again, poor ocular surface health or unreasonable expectations. All right, let’s see. What is the reason for the low limit on astigmatism correction? I just mentioned that it doesn’t correct as much astigmatism. It tends to correct maybe half of it. Even with the lenses that have toric peripheries, or dual axis types of designs, they don’t really correct more astigmatism, necessarily. They just really help improve centration. Ideal age to start treatment as myopia control? I say the earliest possible. As long as the child can tolerate it and understands what the procedure is going to do on a nightly basis, and as long as the parents agree to it. If you can start treatment when they’re -1 or -2, versus waiting until they’re -3 or -4 or -5, it’s definitely better. Is it safe for patients who have used ortho-K for years to undergo LASIK? In my experience, it is. They have to wait until their cornea normalizes again. And I recommend waiting for at least a year. Longer if they can, because you want to also make sure that they’re not gonna progress. Because one of the requirements for having LASIK or other refractive surgeries is that their vision has to be stable. The refraction has to be stable for at least a year. So I would wait at least a year, if not longer, to make sure that their cornea has stabilized and make sure the refraction’s stabilized before going through refractive surgery. All right. So in terms of baseline examination, you want to do all these things. HVID or corneal diameter helps to determine the diameter of the lens you’re going to use. Typically you’re gonna be about… Oh, half a millimeter or so, maybe a millimeter smaller than the corneal diameter. And you can — that gives you room to go larger, if you need to. But you don’t want to go too small, because you don’t get good stability of the positioning of the lens. Pupil size may be more important for adults, because they tend to complain more about nighttime glare. For children, not as much of a concern. Small pupils in a child is unusual, but that might limit the effect of the myopia control. Corneal topography, like I mentioned, is essential. You want to make sure they have normal topography, and are not subclinical keratoconic, for example, and also that will help you monitor treatment over time. All right. Next poll question. How many FDA-approved ortho-K designs are there? 2, 5, 12, or they’re all FDA-approved? All right, so most people said 2. Some people said 5, a few people said 3, and some said they were all FDA-approved. Actually, the answer is 12. I’ll show you that in just a few minutes. All right, so in terms of lens design, the basic lens design is similar for all of these designs. They are all reverse geometry designs. They have a central base curve or a central zone that’s really flat compared to the cornea. There is this fitting or reverse curve, that — because the base curve is flat, it brings the back surface of the lens back down to the cornea. And there’s this area called the alignment curve or alignment zone or landing zone, which is supposed to be roughly parallel to the peripheral cornea. And then there is a peripheral curve. The landing zone can be a flat zone, like in the Paragon designs, or it can be actual curves. And there tends to be two curves in this zone, for most of the other designs. They tend to have large diameters, typically between 10.5 and 11 millimeters. Could be a little smaller, a little bigger, if the patient’s cornea is smaller or larger than that. How pupil size has effect on myopia control — is the treatment zone less or more than the pupil size to have the best myopia control? Good question. I mean, interestingly, most of these designs have an optic zone that’s about 6 millimeters, and if you need to correct more than 5 or 6 diopters, that actually decreases, so that you can flatten more centrally, and get more myopic correction. The pupil size, I think, is only important in that you want to have some of this peripheral light that’s going through this steep zone in the midperiphery of the cornea to get into the eye, for myopia control. If it’s not for myopia control, that’s probably not important, and in fact, the smaller the pupil, the better their vision will be for distance, because they’re not seeing through much of the steeper cornea out here. Should kids with intermittent exotropia and myopia be considered as bad candidates considering they need constant clear vision to control their strabismus? Possibly. One thing that can help exotropia is if they have to accommodate a little bit. And with ortho-K treatment, they don’t necessarily accommodate more or less than other types of treatment. It’s not necessarily a contraindication, but if you’re counting on some accommodation to help them control their exotropia, then ortho-K may not be the right kind of treatment for them. All right, so… We already looked at this, how the lens fits the cornea. We want the base curve to be flatter than the central cornea, with a very thin tear layer, less than 10 microns of clearance there. And that creates a compressive positive pressure centrally. And in the reverse curve area, it’s steeper and further away from the cornea. That creates a negative pressure that pulls the cornea out. And you have an alignment curve in the midperiphery that creates some mild compression, so actually you have two compressive zones, in the center and in the periphery, and in between that, you have this negative pressure zone that brings the cornea out. And the more pressure you have centrally and peripherally, the more this midperipheral part comes out, and the more myopic correction you have, and the more myopia control effect you have. In terms of the base curve, how flat do you make the base curve? Typically the base curve is made flatter than the K reading, central K reading, by the amount of refractive error you’re trying to correct, and another half to diopter flatter than that, which is like… A regression factor. You know, you want to correct more and not less. Maybe push them a little bit into hyperopia for when they first take the lenses off, so that they maintain good vision throughout the day. So, for example, if your patient has a K reading of 44 diopters, refraction of -3, the base curve is gonna be maybe 3.5 diopters flatter than the K reading, so the base curve will be about 40.5 diopters. Again, the optic zone is generally 6 millimeters in diameter, and that allows you to correct about 5 or 6 diopters pretty comfortably. Comfortably and predictably. Okay. So that’s the base curve. The reverse curve is designed to bring the edge of the back surface back towards the cornea. So it depends on how flat that base curve is. That reverse curve can be a single curve, or it can be a sigmoid curve, like in the Paragon design. But it’s designed to bring that back surface back to the cornea, and it’s gonna create this area of clearance out here that you see in the fluorescein patterns. It has different names depending on the design that you’re using. And then you have the alignment curve, which is out towards the periphery of the lens. That’s designed to be in alignment with the cornea, or maybe even a little bit steeper than that peripheral cornea, to create a mild compression out there, and that also allows the lens to stabilize and stay centered on the cornea. So if you’re having a problem with the lens going offcenter, sometimes that alignment curve is the part of the lens that you’re going to adjust to make it fit better. Does eccentricity affect the result of lens fit? It certainly does. Most of these designs, as — I don’t have much longer, but if we had time to talk about them — are only designed based on K readings, refractive error, and HVID. They don’t take into account eccentricity. So you have to make adjustments based on that. How would the vision be with the lens on? It would be clear, because even though I mentioned that you’re going flatter than the cornea by a certain amount, what they do is, when you have a base curve that’s flat, they adjust the power so that it corrects their vision. And in this case, the power of the lens needs to be +50, because the lacrimal lens is -3.50. So you need the lens to be plus 0.50. So when the patient puts the lens on, they will have clear vision. And that’s one of the ways we can tell if the patient is becoming more myopic. We have them put the lens on and then check their vision. If their vision is still clear, with no overrefraction, then we know their eye has not become — the axial length hasn’t increased. If they are taking minus over the lens, then they’ve probably increased in myopia. Here’s some examples of ortho-K designs. In the US, there’s two umbrellas for what’s FDA-approved. One is the Paragon CRT, corneal refractive therapy lens, and the other is the Bausch and Lomb vision shaping treatment or VST system. The VST system actually consists of 11 different designs. I work with four of them. The DreamLens, the Emerald, the BE Retainer, and the WAVE design. The simplest is probably the Emerald, because they just need Ks, SR, and are HVID. The others are a little more sophisticated, especially the WAVE design. It takes a little more time to learn how to use those lenses. Here are the Bausch and Lomb designs. You don’t have to be approved in all of them. And each one requires that you be certified in their designs. If you want to be certified in all of them, you have to do 11 certifications. Just to show you how simple the CRT design is, they just have a chart and you just take flat K and the spherical part of the refractive error, and you determine the lens design based on that. So, for example, if their flat K is 44, and refraction is -2, -0.75, axis, 180, you’ll pick this lens, and that’s the starting lens, and you just go from there. Here’s an example of the DreamLens online design program. You just plug in refraction and their Ks, and it will calculate it for you. Here’s the WAVE design, based on their corneal topography and the refraction, and it’s a lot more sophisticated in how you design the lens. That’s a whole nother lecture, talking about how to design their lenses. I’m not sure if we should continue. I have a few more slides, but we’ve already gone to 50 minutes. I’m happy to continue on with this, if it’s okay with the attendees and with Lawrence. But I think we’ve come to the end of the time. But anyway, I’ll continue until someone tells me to stop.
>> Yeah, Dr. Watanabe, you can continue and answer some more questions.
DR WATANABE: Okay, great. In terms of selecting a design, it’s really up to you. The designs that I have become certified on are based on my experience with them, based on what colleagues have experienced. Sometimes I’ll try a design, and if I don’t like it, I’ll stop using it. But it’s really based on what I’ve heard about designs and talking to colleagues about them. So you may start out with a design, and decide that over time it’s really not working for you and try something else. That’s perfectly fine. In terms of… Once you’ve designed the lens or selected the lens or talked to a consultant about the lens design, you dispense the lens. Have the patient come in, basically dispensing this to make sure the lens looks like it’s fitting properly, and to make sure the patient has good vision with it. Make sure that the patient is gonna be able to tolerate the lens. The patient should be 20/20 with the lens on, assuming they have a best corrected vision of 20/20. Do an overrefraction just with loose lenses. They should be near plano, plus or minus 0.25 diopter. 1 to 2 millimeter ring of clearance, and then alignment in the midperipheral zone. Another poll question. I’ll just… Actually, let’s do this poll question real quickly. What is the purpose of doing the overrefraction over the lens? I kind of briefly mentioned why we check vision. With the lens on. Okay. So the purpose of actually doing the overrefraction is not to make sure the lens power is correct. It’s to make sure the base curve is appropriate. Because if, again, talking about the power of the lens, if the lens curve is proper, then the patient should have good vision with the lens on. If there’s overrefraction, then the lens is either too steep or too flat. If you’re finding myopic overrefraction, that means the lens is not flat enough, and that’s usually because you didn’t select the lens properly in the beginning, or the patient — if the lens was proper in the beginning, then they have become more myopic over time. All right. So if the lens fit and vision are acceptable, do your education. Make sure they understand how to properly take care of the lens. And when they come back, this is my follow-up schedule. The first day or within the first couple of days, to make sure that the cornea looks good, and the lens is centering properly on the eye. Usually I will let them go for at least two weeks, before I assess if we need to make changes. Unless something is really, really off in the first week, I’ll just continue with treatment until two weeks. At two weeks, you should know if the treatment is working. If the treatment is not working enough at two weeks, that’s when I definitely start making changes. And the most common treatments are for lenses that are either decentering or lenses that are just not providing enough treatment. Assuming that the lenses are doing well, I’ll see them at one month and maybe at three months, and then at six months, and then every six months after that. If they don’t come in every six months, we call them to make sure they come in. Because lenses start to change over time. They become deposited, they become scratched, they become chipped, and because of that, corneas may start to be affected. So I definitely want to see them every six months, and then I also want to make sure that they’re maintaining good vision. If they’re still progressing, we’ll need to keep up with the treatment by changing the lens. On follow-ups, check their uncorrected acuity. Do a refraction, to see how far off you are. From your desired treatment effect of plano. Autorefractors tend not to be that accurate. Definitely do a slit lamp, with and without fluorescein. Look at the lens quality every six months, and if you’re doing myopia control, you can actually measure axial length as another measure to see if it’s working or not. Okay. Are retainer lenses always needed? The answer to that is yes. This is never a permanent treatment, and they’re going to have to continue to wear the lenses as long as they want treatment. After they stop treatment, their eyes will regress and they’ll go back to baseline refraction, assuming they haven’t become more myopic. In terms of vision, we expect 20/20 or better. And if they don’t have 20/20 vision, then they’re having some sort of problem. Undertreatment is either because you don’t have the accurate base curve, so you should know that by doing the overrefraction, or because the lens has too much sagittal depth, meaning the base curve is not close enough to the cornea. So do an overrefraction. If you’re not within 0.25 diopter of plano, change the base curve. If the lens is too far away from the cornea, you need to decrease the sagittal depth, and you do that by changing either the reverse curve, flattening the reverse curve, or flattening the alignment curve. You never change the base curve to change the fit. You want to leave the base curve alone, assuming it’s accurate. Glare and flare. You’re gonna get some glare and flare, but if you have excessive decentration of the lens, you’re gonna have to improve that. Doing corneal topography — you should get a nice center treatment like this, and a fairly decent treatment zone as well. When ortho-K treatment is decentered, which lens parameter should never be changed? I just mentioned this. You should never change the base curve. You can change everything else, but never change the base curve, assuming you have the correct base curve. If you have decentration and the lens is riding high, usually that’s because the lens does not have enough sagittal depth. You want to increase it by steepening the reverse curve or steepening the alignment curve. If you have the opposite, where the lens is riding too low, and you have a low treatment effect, then usually the lens is too steep, and you have too much sagittal depth. So in this case, you want to decrease — I’m sorry, flatten the reverse curve or flatten the alignment curve. If the lens is too steep, you might also have a central island that develops, where you have vaulting. This one doesn’t have a really good treatment zone here. It’s a little bit too steep. Or a little bit too much sagittal depth. The lens is not close enough to the cornea, so you’re not getting enough flattening centrally. So you want to flatten the reverse curve to get the lens to sit closer to the cornea centrally. If you have lateral decentration, which is a pretty common problem, it might be really hard to manage. It might be the patient is sleeping funny, sleeping on their eye, causing the lens to move, or the lens is just not big enough. The most common way to improve this is to make the lens bigger. But against the rule corneas are really tough to treat, so just be careful of that, when you’re selecting your patients. Another big problem is corneal staining. Corneal staining has a number of causes. Some of them can be very significant. So you want to make sure that you don’t have any corneal staining on follow-up. They can cause blurry vision, discomfort, corneal distortion, and so forth. This is a significant amount of corneal staining, caused by a lens that’s adhering or sticking to the cornea. In the morning. Sometimes all you have to do is use a thicker wetting solution. Sometimes it’s because the patients are just popping their lenses off in the morning without loosening them. Lenses do dry up a little bit overnight and may stick a little bit at night. It’s not necessarily a bad thing, but you want to make sure they put some lubricating drops or saline into the eye before they take the lenses out, use their lid to gently nudge the lens out of place, and once it’s moving properly, they can take the lens out, and this solves most of these staining problems. However, if it doesn’t, maybe the lens has too little sagittal depth and is bearing on the central cornea. In that case, you need to increase the sagittal depth, usually by steepening the reverse curve. Sometimes this is caused by an old lens, and in those cases, you just have to replace the lens. Okay. So I think I answered the first question, second question. Minimum number of hours to wear the lens at night? I tell patients ideally eight hours, but if they wear the lenses at least 6 to 8 hours, I think that’s fine. You usually get enough treatment that way. What is your instrument to measure axial length? In the College I use IOLMaster. What changes in cornea due to ortho-K effect after the measurement? Alter the measurement? Well, the decrease in corneal thickness, epithelial thickness, may affect it a little bit, and also the flattening may affect it a little bit as well. What is the best retaining drops for ortho-K? I like using the natural ortho-K drops. They have a thick and a thin drop. But you can use unpreserved saline. I have some people just using unique pH. I don’t like Boston SIMPLUS. The preservatives are harsher. Cause more problems. But you can use that as well. Unpreserved is the best, but you can use Unique pH, if that works for you. Peripheral staining is usually tight peripheral curves. Or lack of tear exchange. Poor lens care. You know, you want to make sure you’re using good products and having them use them properly. And then I’ve had a few patients have problems with hypoxia. Most of these lenses use Dk of 100 material, 90 to 100, which is definitely sufficient for most people, approved for extended wear, but you can use higher Dk materials. In patients who have oxygen-related problems. A little bit off-topic, but you mentioned sleeping on the eye can change the lens from proper working. Does sleeping on the eye give more astigmatism without ortho-K lenses? Good question. I’m not really sure. I know just pressing on your eyes through your lids can change your refractive error, so I suppose that’s possible. It seems like the upper lid, if you have a really tight, thick upper lid, sometimes you get that topography, where you have a lower steep zone because of that, so I’m sure sleeping on the eye can cause changes in corneal topography. IOP after corneal treatment tends not to be affected, as far as my experience has been. What would be recommended in glaucoma patients? I would not recommend it in glaucoma patients, just because those patients are on drops, usually at night, and you probably don’t want to do anything that might affect corneal health. In most patients, you may notice an iron ring that’s gonna occur where the tears pool in the midperipheral cornea. No issues with that. Just something that you might notice, and know that that’s not significant. And we already mentioned microbial keratitis. And the best thing is just to make sure that the lens is in proper hygiene, proper lens cleaning products and lens cleaning habits, and coming back to see you when they’re supposed to. Okay. That really concludes my lecture. I did have some case studies that I’m afraid we won’t have time to go over. For those of you who want my PowerPoint presentation, the case studies will be included in that. So I’m happy to let you go through that. On your own. And if you have any questions, you can always email me. One final question: How about the recovering of corneal epithelium after the treatment? Like I said before, the corneas tend to go back to baseline after treatment is completed. And that includes epithelial thickness and number of cell layers. So you should assume that that’s going to happen, and that’s what I’ve noticed in my patients who have stopped treatment. At least, I don’t really do histological studies on their corneas, but in terms of corneal topography and refraction, and biomicroscopy, they go back to baseline. All right. So I will stop here. If there are any other questions — one more question? Oh, you’re welcome! Thank you for attending the webinar. And I’m sorry it ran over. I hope this was good information that will help you in your practices, and help you if you’re currently doing ortho-K. And myopia control. Or if you’re thinking about doing ortho-K as a treatment for myopia control. For me, my patients, it’s been a really good option. And for the vast majority of my patients, it’s been a very successful treatment. And I’m definitely going to continue doing this treatment and offering it for my patients. So thank you for your attention and your great questions. And I wish you all well.