Lecture: Introduction to Orthokeratology

During this live webinar, we will discuss a brief history of Orthokeratology, considerations in fitting Orthokeratology for both kids and adults, as well as basic lens design and troubleshooting.

Lecturer: Dr. Anita Gulmiri, OD, FAAO, New England College of Optometry, Massachusetts, USA


DR GULMIRI: Hello, everybody. My name is Dr. Anita Gulmiri. It’s nice to be here today. If you give me a moment, I’m gonna share my screen with you all. All right. So today we’ll be talking about orthokeratology. Just to give you a little bit of a background on myself, I’m currently faculty at the New England College of Optometry, and I work with optometry students in our contact lens clinic, fitting adults in our myopia control clinic. I’ll be going over a very brief surface level introduction to orthokeratology, which in my clinic is a fairly popular treatment for those that wish to be independent of actual visual correction such as glasses or daytime soft contact lenses. Or others that do not want to undergo refractive surgery. So like I mentioned, we’re also fitting children. Most of you probably know there’s a lot of buzz around orthokeratology as a treatment for myopia management or myopia control. But for this presentation, we’ll be discussing orthokeratology basically irrespective of the myopia control piece of this. And I do want to bring in a lot of the myopia control elements and discussing more about orthokeratology perhaps in a later discussion. But for our discussion today, we’ll go over how to determine whether your patient can be — is a good candidate for the treatment. And we’ll review one of the more popular designs we use at our clinic, and how to select the initial lens, and how to troubleshoot some of the things you might run into, when you’re fitting these lenses. So to give you an introduction on orthokeratology, so it works to temporarily correct refractive power. A rigid gas permeable lens is worn overnight to reshape the corneal curvature so that during the day there is almost little or no dependence on corrective glasses or daytime contact lens wear. More often than not, we’re using this type of treatment to correct myopia. But it can be used to correct hyperopia in some cases. And even presbyopia in other cases. Another name for orthokeratology is called corneal reshaping. And so some of the treatment systems and one in particular that we will discuss — they’ve kind of deemed their designs corneal refractive therapy, CRT, or vision shaping treatment, VST. And these are all names of their proprietary systems. Here’s a diagram of — let’s start with this here. The yellow line here. Which is just a tricurve RGP. And with modern orthokeratology, these lenses typically come in multiple zones. But just to give you a basic understanding of kind of how it relates to your traditional or your standard tricurve design, with orthokeratology, the central base curve is actually flatter than your secondary curve. Right? That’s unlike a regular or normal GP. And so the secondary curve is called the reverse curve. Also known as a reverse geometry curve. And so this is what kind of allows for orthokeratology to work. Because we’re compressing the cells here, the tear film here, and correcting it in these areas here. And lastly we have the peripheral curve. And this essentially serves basically the same purpose as your typical tricurve or GP design, where it’s essentially the landing curve or responsible for edge lift here, exchange, things like that. All right. So I want to get… I just want to test your knowledge here on the subject matter a little bit. So we’ll start off with our first poll question. Number one. Modern accelerated orthokeratology consists of which of the following? High Dk gas permeable lens materials, reverse geometry lens designs, overnight lens wear, or all of the above. All right. Great. So most of you picked the right answer. So it is all of the above. So we’ll go into this in a little bit more detail here. So with orthokeratology, it’s been used since the 1960s, in one form or another in the United States. George Jessen first attempted to deliberately correct refractive error using rigid contact lenses, using a technique called Orthofocus. And the basis of traditional OrthoK — we’ll call it traditional OrthoK — was to fit progressively flatter lenses to mold and change the refractive power. And typically the correction was worn during the day. So not overnight. And thank heavens for that, because the Dk of those materials was quite low. Very low oxygen permeability. So you can imagine wearing at night created all kinds of issues. Or would have created all kinds of issues. The average reduction was between 1 diopter and 1.5 diopter, which again can have a lot of variability, and poor predictability. Typically, additional astigmatism was induced, as well. The limitations of the traditional OrthoK designs included long-term data at that point, on both safety and efficacy. And then topography imaging hadn’t been around, so only the central keratometry readings were being used to design these lenses. And again, these were designed increasingly in flatter base curves, to keep up with the flattening corneal curvature. So it posed an issue, as far as safety concerns go. And then the material that was used was PMMA. And far from the high Dk materials that are available today. And some of you might already know — with PMMA, it is a rigid material, but it’s not gas permeable. It has a very low oxygen permeability. And so they thankfully weren’t doing overnight wear. But that wouldn’t have been accepted either. And then the effects would take multiple weeks to multiple months. Again, various variability. And the timing would kind of not be as predictable. And then the refittings would take multiple lens treatments. They would continue to refitting flatter and flatter until the desired result was achieved. Modern orthokeratology, on the other hand, allows the patients to wear the lenses during nighttime only. So overnight, and then the materials that we’re using are FDA approved, and they’re hyperDK materials for overnight wear. It’s been approved in 2002 for the treatment of myopia only. I want to make a point to highlight that: Yes, OrthoK has been approved for the treatment of myopia, but that’s not the same thing as the treatment of myopia management or myopia control. So the FDA hasn’t granted approval for myopia control. So when we deal with our patients in the myopia control clinic, we are educating them on this. In great detail. They need to know that the treatment itself is FDA approved. But it’s not FDA approved for the purposes that we’re using it. So we do have an informed consent that indicates this. And we do kind of lay it out there, so that they know they’re kind of agreeing to an off-label treatment of the myopia management and myopia control. Okay. So again, the materials… The availability of the high Dk materials have contributed to safe overnight wear. The higher oxygen material made it somewhat okay for the lens to sit in a closed lid environment. So the newer RGP lens design creates corneal shape changes, so that the refractive correction can last throughout the day. The night wear regimen is one of the biggest advantages of modern orthokeratology. And it’s perhaps the primary reason why it’s becoming so popular for myopia control as well. And then the RGP design — we kind of discussed a little bit earlier as well. So it’s a reverse geometry lens, versus the flatter conventional GP that was used previously. And then we’re also utilizing corneal topography. You know, almost for every visit. So that’s been excellent in helping us understand the corneal shape and the effects of OrthoK treatment. It’s helping us to monitor changes that are occurring overnight. The best way to tell how that lens is positioned overnight is to evaluate it using the corneal topography. So that is something that we’re using almost exclusively when it comes to the follow-ups. So I discussed this already, but just to review again, we are using a reverse lens geometry design, where the base curve or the central curve is flatter than your secondary curve. And so this is the opposite or reverse of a traditional GP lens. Where the base curve is actually steeper and the secondary curves are progressively flatter, as we get towards the edge of the lens. So these modern day lenses are designed to reshape the cornea. They consist of multiple zones, typically about three to four zones. Most of the manufacturers that we deal with have a proprietary lens design. So a lot of times, we don’t know the specific lens curves and parameters that they’re using, except for just the base curve diameter and power. They have different nomenclatures for different elements of the parameters. Like the return zone. You know, some of them — the reverse curve part of me will call it return zone, and we’ll go into this in a little bit more detail. Some of the other advantages include improved treatment centration, and so there’s less decentration and less corneal distortion than the previous traditional OrthoK lens designs that weren’t reverse geometry designs. And then again we have improved predictability. This again is one of the designs that we’ll go into more detail with. But we have your base curve, you have your return zone, or your reverse curve here, and then you have your landing zone or your edge lift at the bottom here. So most of the time, we’re looking at about three to four different curves. And the curves that vary — so some of the four curve designs have a separate alignment or fitting curve over here. That can be manipulated as well to achieve a better fit or better centration. So how does OrthoK actually work? Effectively, we know there is some level of corneal curvature flattening. And midperipheral curvature steepening. But we don’t quite know exactly how this phenomenon occurs from a physiological standpoint. One theory is that the fluid within the central epithelium is compressed, so there’s no loss of cells and no cells actually move, but fluid within these cells moves, and that’s what gets dispersed. This hypothesis is that a thin layer of tear film exists between the back of the OrthoK lens and the central cornea. And these tear film shear forces — they act hydraulically to create a force compression, when the eyelid is closed. There’s another theory that says OrthoK wear changes myopic correction by actually bending the cornea to reshape it. And then we know these changes are temporary. So the cornea is elastic. And has a memory. So the cornea will resume its pre-OrthoK shape once lens wear has been discontinued. Histologically speaking, this is kind of what we’re seeing here. We’re seeing the central cornea is thinning. And then your midperipheral cornea is thickening. Is getting thicker. And then the epithelial cells are really what is contributing to most of the change here, rather than the stromal cells. And then from this photo here, really it’s just highlighting that effectively a post-lens tear layer with a thickness differential is created, that results in areas of positive pressure, centrally, and then the negative pull force in the midperiphery, that’s causing that steepening effect. All right. So moving on to lens — sorry, patient selection. So both children and adults are good candidates for orthokeratology. Like I said, in my clinic, we fit both children and adults. Patients who participate in sports and other physical activities are excellent candidates for OrthoK. Normally gas permeable lenses — we don’t typically recommend these for contact sports, because with rapid eye movements and physical trauma, these lenses can dislodge. And then soft contact lenses in some cases — like swimming and other water sports — we don’t recommend. Because of risk of infection. Or sometimes the soft lenses can dry out, if you’re spending a lot of time outdoors. Skiing or running. So orthokeratology then, in that sense, can be a good way to go. Which requires no lens wear during the day. So it’s a really good option for patients that are active. And then for presbyopia too. We have some patients that — they don’t need full-time near correction. And so they may find that their near vision is something that they’re not necessarily needing. So we can fit these patients for distance only OrthoK, and then they would wear reading glasses for any time that they needed near work. And these tend to be more pre-presbyopes or early presbyopes. Once they start to be a little more advanced in their presbyopia, OrthoK doesn’t work as well, unless we try to do some monovision OrthoK. One thing to note: If you do have early presbyopes that are fit into OrthoK, and at this point, they may not need any full-time near correction, when they do undergo OrthoK, they may find that their near vision is not as clear in the morning, immediately after lens removal. Because that’s when the OrthoK effect is at its maximum. So because the initial target for OrthoK — and we’ll talk about this in a little bit more detail — is anywhere between +50 to +75, this creates additional accommodative demand. The target becomes a little bit hyperopic. The idea is that there’s a slight regression during the day, so that towards the end of the day, you’re not negatively affecting the distance vision. So when we’re educating these presbyopes, regarding their visual expectation, it’s really important to mention that that slight hyperopic refraction in the morning may kind of hinder their near vision. So they can wear low plus reading glasses in the morning, or their target can be cut back a little bit, so we can make the target less hyperopic, so in the morning, they’re still able to read. But then this kind of has the drawback that the distance vision will be slightly blurrier at nighttime. Like I mentioned earlier, another possible strategy for presbyopic patients is performing a monovision correction on them, which we can do by correcting the non-dominant eye. This may work well for patients who are already in a soft contact lens monovision, for example, or someone who hasn’t actually experienced monovision, we may want to do a soft contact lens trial for a few days, before we start to do the OrthoK treatment. Again, if the patient can tolerate monovision, then we can kind of pursue OrthoK. Because OrthoK fitting is a lot more involved than just a soft contact lens fitting. And then we have to make sure, when we’re thinking about which patient is a good candidate, the motivation needs to be there. There is a lot involved when it comes to fitting OrthoK lenses. So the commitment of all the appointments that the patient needs to come to needs to be there, as well as making sure that they’re committed to wearing the lens on a nightly basis. I have to say the lens does feel like you have an eyelash in your eye. It’s not as comfortable as a soft lens. At least initially. So they have to be okay with the benefits of the treatment. Continuing on with it, even though the comfort might not be where they want it to be. And then the cleaning regimen — they have to make sure they’re cleaning the lenses well. For patients that don’t want to wear the lens every night or can’t wear the lens every night, and they skip a night, they have to understand that the vision might be blurry the following morning. Compliance in terms of cleaning the lens, as I spoke about just now — it’s really, really important with these nighttime lens wearers that we’re extremely vigilant about cleaning the lens. We’re giving them the highest standard when it comes to safety. There has been reported cases of microbial keratitis with orthokeratology. So we have to make sure that we’re ensuring that patients are cleaning their lenses properly and following our directions. Patients should also be made aware of these expectations about the cleaning. I won’t go into detail here, but making sure that they’re wearing the lenses on a nightly basis as well, and like I said, not skipping them, and not wearing them in the daytime. I’ve had patients wear the lenses during the day too, because as you may already know, the lenses — when they’re on the eye, they actually do provide really good vision on the eye. So I have had patients just wear them during the day. Because they’re like… Oh, during the transition period, they see really well with them. So they continue to wear them. The expectations — and we’ll go over this in a little bit more detail again in the next slide — but the expectations need to be there. The patient needs to know about the financial and the time commitment that’s involved as well. When initiating the orthokeratology. The cost varies. Between thousands of dollars for the first year — that’s kind of around what we charge at our clinic — including the lenses. Most of the time, there is no insurance benefit for these types of contact lens fittings. So it’s not considered medically necessary at this time. At least, not in the United States. So the benefit actually is fairly limited. And so a lot of the cost is out of pocket for the patients. And it is the highest the first year. It is something that we educate the patients about. Though there will be a cost, subsequent years. It is the highest the first year. And then every 12 months or so, we do recommend replacement of the lenses, so that’s an additional cost as well. All right. So selecting patients based on their parameters. So the FDA approval for the Paragon-CRT design, which is what we’ll go into more detail about, it goes up to -6 diopter for myopia, and the astigmatism goes up to 1.75 diopters of astigmatism that can be corrected. And that’s regular astigmatism that we’re correcting. In general, patients with higher refractive errors are more difficult to treat. With a lower percentage of these patients achieving the targeted endpoint. And greater amounts of astigmatism, of course, are more difficult to treat. And you may need a toric OrthoK lens for these patients. The best result is patients that have low levels of myopia and low levels of astigmatism. Against the rule astigmatism is more difficult to treat, compared to with the rule astigmatism. And I can’t emphasize the importance of topography enough. We have to make sure we’re doing baseline topography. And if you’re evaluating for astigmatism here, you want to look to see if that astigmatism is central, versus limbal to limbal. If it’s more limbal to limbal, then we know that we’ll probably need a toric OrthoK design. Otherwise, that lens will rock on the cornea quite a bit, and you won’t achieve a stable fit for your lens. So poor candidates… Kind of alluded to this a little earlier as well. Anyone greater than 6 diopters. You can fit them off-label. Past the FDA approval. But they tend to have poor results. They have smaller treatment zones. So a lot of times, at night, they can have more glare, shadows, and things like that, when the pupil is dilated. Anyone having greater than 1.75 diopters of astigmatism, or against the rule astigmatism that’s greater than 0.75 tend not to be great candidates as well. Again, the astigmatism — if the patient is educated that they may have residual astigmatism, sometimes we do this, and we have them wear corrective glasses on top, towards the end of the night, for example. And then the patient can’t have amblyopia, can’t be someone that’s non-compliant, that won’t listen to your treatment suggestions or recommendations on cleaning and things like that. And then it’s really, really important to test the corneal integrity. Or check the corneal integrity. Pardon me. When we’re looking at these. So we want to make sure the patient doesn’t have any sort of disfigurement on the cornea. We want to make sure there’s no keratitis, or keratoconus. Keratoconus we can also pick up on the baseline topography that we do. If the patient has severe dry eye, EBMD, or any sorts of acute inflammation, these are poor candidates for OrthoK. So it’s a good idea to kind of stop the buck right there. And have them try something else, especially if they have conditions such as keratoconus. All right. So what do we do at our consultation exam? So we do a manifest refraction. I also do a cycloplegic refraction on all our pediatric patients. We do our baseline topography. The topography also gives us the eccentricity measurement, which tends to be helpful for when we end up having some issues with correction. We do a horizontal visible iris diameter measurement. We check the pupil diameter. We check for lid position and tension. And then we again assess the cornea. So again, more of a summary slide here, but just to highlight, we need to appropriately and thoroughly educate our patients on the benefits and risks of OrthoK wear. Like I mentioned earlier, there have been reported cases of things like microbial keratitis that has been prevalent in OrthoK wear, and a lot of times, we have to make sure our patients know about this, so that they not only have that fear of making sure that the lens is nice and clean every night that they’re wearing them, but also to make sure that they’re aware of all of their risks and benefits that come with OrthoK lens wear. So the predicted amount of myopia reduction needs to be kind of educated. We need to make sure that the patient knows — especially if they’re on the higher range of myopia — no daytime correction needed. And that again goes to that they cannot wear that contact lens, the OrthoK lens, during the day as well. It is a good alternative to refractive surgery. So children are great for using OrthoK. Children that are — children that we know are not candidates for laser vision correction or refractive surgery. So this is a great alternative for children. I had a question in one of the questions that you submitted. What’s the youngest age we fit in our clinic? So the youngest age we fit is five years old. That is a fairly young age. But we have to make sure that the parents are very involved in those cases. And in our cases where the patient is younger than 6 years old, we actually have the parents be the ones to do the insertion and removal. So the child is at that point just basically… Not learning the insertion/removal yet. And the parents are fully involved with that. As they get older — the cutoff is 6 years of age. At 6 years of age, we try to teach both parent and child insertion/removal techniques, with the goal that eventually the child will learn, if they don’t initially learn right away. We have to educate the patient that it is reversible and temporary. So if the patient is not wearing the lenses on a nightly basis, the reversibility kind of kicks in here, and that they won’t have good vision the next day. With that said, it’s also a benefit of the treatment that it is temporary. So if the patient wants to stop OrthoK wear for whatever reason, they just have to stop wearing the lenses, and over a course of two weeks to one month, they will… Their vision will come back to baseline. We discussed myopia control. And that it’s not FDA approved for the purpose of myopia control. Safety of lens wear. It is a contact lens. So it does bring in all the complications associated with contact lens wear. Especially when we’re thinking about wearing these overnight. Arguably, it can be safer than surgical options, but since — because the treatment is reversible, so that’s a good point. Comfort is less comfortable than soft contact lenses, as I mentioned earlier. I usually described it to my patients as an eyelash in the eye. We do — the very first time, we do put the lens on the eye. We do use a topical anesthetic. So that the initial comfort isn’t — there’s a gradual period to the discomfort, if you will. And then since the eye is closed mostly, the comfort tends to be less of an issue as the patient kind of wears the lenses, you know, with the eyes closed, and they’re sleeping for a majority of the time they have the lens on. OrthoK lenses also tend to be larger in diameter than traditional GP lenses. They range from — the minimum we fit is 10 to 10.5. That’s the smallest diameter we fit. Because they tend to be a little bit larger than traditional GP lenses, the comfort is a little bit better than GP as well. And aberrations. I talked about this earlier too. If your patient has a higher refractive error that we’re correcting, they’ll have a smaller treatment size, at night, they’ll have a bigger pupil, so higher induced aberrations. A child usually has a bigger pupil size than most adults do, so they tend to experience more aberrations, although they’re not very vocal about those aberrations. Again, keeping in mind that there are some induced aberrations as well. All right. So how long does the treatment take? When we’re discussing these visual expectations, we have to make sure we’re keeping in mind that the individual patient and individual eye and the treatment effect will depend on the amount of correction and the refractive error that we’re correcting for. So on average, it takes about 10 to 14 days for us to reach our goal. But it could take up to 30 days or so, depending on the correction. Typically, we recommend our patients wear them for at least 7 to 8 hours on a nightly basis. And again, do not wear them during the day. One thing to note about wearing them during the day is that the treatment actually doesn’t sit properly, because of the movement and the lid interaction, and so it disrupts the actual centration of the treatment if the patient is wearing them during the day. And the lens is moving around on the eye. More on visual expectations. After night one, likely they’re still gonna need their refractive correction during the day the next day. So if they have glasses, we’ll still ask them to wear them. Especially towards the end of the day. During the first week, like I said, they’ll probably still need their correction. But mostly towards the end of the day. Depending on their pre-OrthoK refractive error. If it was on the lower side, less than 2 diopters or so, at week one, they might be seeing 20/20 or better acuity. And then two weeks to one month — no correction all day. So that’s what we aim for. Is that at the two week mark, when they come back for their two week follow-up, I hope that the visual acuity uncorrected is right at target or where I want it to be. Okay? So during the interim period, when they’re adjusting to things, they can wear their glasses, or we do daily soft lenses that they can use in increasing — sorry, decreasing power. As the days progress. So for some older adults, that’s kind of what we’ve done in the interim, to ensure that they’re still corrected during the day. When they’re going through the process. And then, again, making sure that our patients know about those glare and halos that they might experience, especially at night. So poll question number two… Which one of the following is a component of the Paragon-CRT design? We’re gonna go ahead and discuss some of the particulars of the Paragon lens. I don’t know if you’re all familiar with this, but let’s see how much you know about the Paragon CRT design. The return zone that is specified by radius of curvature, landing zone that is specified by sagittal depth, base curve that is specified by its angle with respect to the central cornea, or none of the above. All right. So this one is a little bit tricky. And I wanted to see, you know, how many of you were familiar with the Paragon CRT design. I know it’s available internationally as well. So that’s kind of why we do fit it in our clinic. We have a lot of patients that are from China and Taiwan, so they do go back and forth a lot. So it’s easier for us to manage them with a lens that’s available in both places. So the answer actually is: None of the above. And I’ll go over the details and the specificity of all of this as we kind of keep going. All right. So before we begin to fit the lens on our patient, it’s important to know that there is a certification program for every practitioner that is intending on fitting these lenses. And so here’s the information on the Paragon CRT lens. So if this is available in your country, it’s an excellent and honestly fairly easy training to complete. Most OrthoK designs are proprietary, so you can certainly design your own lens as well, using — we’ve used software, such as Wave, before. I find it generally just easier to use a lens that’s already manufactured for the purpose of orthokeratology. But anyways, generally in the United States, you need to complete a certification for any proprietary OrthoK lens design. Because this is an FDA requirement. So when we’re selecting your initial lens, for orthokeratology, there’s different ways to do this. And different protocols, depending on the manufacturer. Some require only keratometry readings and refraction, whereas others require more of a diagnostic fitting, or full topography. So with the Paragon design that we’ll talk about here, for most of our patients, and for teaching purposes, it’s the lens, like I said, that we go to. Part of the reason why I like this lens is, again, the parameters are mostly intuitive and straightforward. And there’s not a lot of choosing to do. So there’s about three things — three or four things that you can change. And that’s it. And so it helps to kind of keep things more simple and achieve a better fitting result sooner. We also have a fitting set in our clinic that looks like this here. That’s a big suitcase filled with lenses. I have three or four of those, and I’ve collected those over the years. The fitting set is nice, because you can actually fit the lens on the patient, to see if the initial lens that you’re choosing is something that will work for your patient. The other option is to order it empirically, like I said, so you can do that by either calling the manufacturer, or using their online calculator. And then there are some designs — and some different brands too — that will allow empirical fitting, where you can actually order multiple different lenses. So the SureFIT design with Paragon, you can actually order three different lenses, of varying parameters, so if the first one that you try on doesn’t fit as well, you can move on to the other lenses. You don’t have to wait until your newly ordered lens arrived into clinic. So the manifest refraction SPHERE is what we need for the initial lens selection, at least for the Paragon design, and then both flat and steep keratometry readings. Like I mentioned, some labs do — we use another lab called Euclid that actually wants the baseline topography as well. So some labs like to have the topography, and they like to make some changes, based on the entire topography of the cornea. So I order my initial lens based on those parameters, and I bring the patient back for fitting and dispense the same day. So prior to having that lens in office, the patient hasn’t tried the lens. Very rarely, like I said, I do have the fitting set in office, so very rarely I will actually fit them with my fitting set, but for the most part, because my kit actually doesn’t come in a toric OrthoK, so especially if the patient needs a toric design or an astigmatism design, I tend to fit these empirically, bring the lens in office, and then I dispense it on the eye. I evaluate the lens — the OrthoK. I make sure I have good centration, good movement, that apical touch, midperipheral pooling, and I’ll show you examples of what the ideal lens should look like here. And then we do insertion/removal or application/removal training, same day. We train them on solutions, cleanings, things like that, and we dispense the lens, same day. So 99% of the time, the first lens that I order, I dispense. Very, very rarely does that lens not fit appropriately, and I have to actually change it. So these manufacturers — I have to give them credit. They’ve gotten extremely good at designing lenses based on very simple things. Like your manifest refraction sphere and your keratometry readings. And most of the time, that first lens I get is good enough, where I can actually send them home. If the child is young, like I mentioned — anywhere between 6 to 8 years of age, we do tend to involve the parents heavily. We make sure that even if the child has gotten the insertion/removal okay, we make sure the parent also knows how to remove the lens, and we use small DMV plungers for the removal technique. We also discuss adverse events and adverse treatments, things that can happen, things that can go wrong at this point. And then we educate them on our — to call our clinic when any of these presents. Redness, pain, discomfort, light sensitivity, anything out of the ordinary, they’re instructed to call us right away. We have an on-call service at our clinic as well that can cater to these patients. So just talking about the parameters when it comes to the Paragon design. This is kind of what the case here looks like. So you have your base curve, which again is flatter than the flat K reading. Plus… Sorry, flatter than the flat K reading by the manifest refraction sphere, plus the additional 0.5 diopters. So that’s kind of how that number is… That’s how they come up with that number. You don’t have to worry about knowing how they come up with that number. But if you’re interested, this is how it kind of works. So if you had a patient, for example, that had a baseline K reading of 44 and 45, you could think of it as… You know… And then a refraction of -2, -1, you would take the -2, add the +50, and subtract that from the 44, which is the flat reading. So that’s typically how they come up with that base curve. The first number here. And then they have the second curve, which is your reverse curve. They call this the return zone depth. So that’s the Paragon term. Other companies call this the reverse curve, or secondary curve. There’s different names that are deemed. So that’s this curve here. It’s the sagittal depth. And then we also have our landing zone angle. So our edge lift, if you will. And so that very, very last curve, the alignment curve, is called the landing zone angle, and that’s responsible for your edge lift. For your lens diameter selection, it’s based on the HVID, and it will have a large effect on centration. So I recommend paying attention to your horizontal visible iris diameter measurement very carefully. We do have an axial length measurement and the topographer as well that measures both of these things for us topographically, however, I also recheck with my ruler every single time. And then a good rule of thumb is to subtract 1 millimeter from the HVID measurement that you’ve gotten. So if you have a 12 millimeter cornea, the lens that you’ll go with is 11 millimeters. The standard lens diameter for the Paragon lens design is 10.5 millimeters. And then based on that, the optic zone is about 6 millimeters. And then the power. When it comes to the power, that’s the target of the prescription. So think of the power as being plus 0.5 for mostly all of the lenses, because again, we’re creating that minus lacrimal lens that fully compensates for the refractive error, plus that additional plus 0.5. And that’s for regression. So that’s for — as the day goes by, we want to make sure that the patient isn’t left blurry towards the end of the day. So on to our poll question number three. Which one of the following is the ideal endpoint corneal topography pattern for a patient undergoing orthokeratology? Do we want a prolate with steep curvature centrally, do we want an oblate design with flat curvatures centrally, do we want an oblate flat zone centrally with small steep central island, or none of the above? Yeah, exactly. So we want that oblate flat zone centrally. 44% of you said that. Oh, sorry, this is the incorrect answer. It is oblate with flat curved centrally. So we don’t necessarily want any sort of steep central island. And I’ll go into that in more detail as well. All right. So when we’re thinking of the anatomy of the OrthoK CRT design, we kind of went over this in a lot of detail already, but to highlight here: You have your base curve, your secondary curve, your return zone depth, which is going to be a little bit more steeper, so that’s gonna be where all the tears pool. That’s the same as this area here, the pooling of the tears that you’re seeing here. And then you have your landing zone angle here, the alignment curve, so that’s gonna be responsible for your centration, as well as your edge lift. One thing that’s also nice about the Paragon lenses. They’re all lasered in. I have a lot of patients that tend to mix up their lenses. This is really, really helpful when I can read the lens and find the lens I do want on the eye. This one says 8550. 50 is short for 500, which is the return zone, and 34 for the landing zone angle. So it has the laser etches on the lenses, which is excellent. Good. So when we’re evaluating the fit, the lens should be fairly centered and should cover about 90% of the cornea, or 90% of the HVID. So when we’re making sure — that’s one of the things I pay attention to a lot. The lens diameter. I want to make sure that that lens is nicely centered, and if it’s not centered, if there’s any lateral decentration, I do have to change the lens diameter. Your fluorescein pattern is going to have that classic bull’s eye pattern. So you’re having that area of central touch, if you will. It’s not technically touch, because there is that thin layer of tear film. And then you have your 1 millimeter or so of paracentral pooling. And then we have a 2 millimeter band of midperipheral alignment or touch, followed by a thinner band, 1 millimeter or so, of your peripheral clearance. Again, you’re looking for that nice bull’s eye pattern that’s centered on the cornea. And then movement. You do want the lens to have some movement. It can’t be bound to the cornea. That’s an unacceptable fit. But it can’t be excessively moving. So you have to make sure you have about 1.5 to 2 millimeters of movement in every position of gaze, without too much decentration past that limbus. So what happens if your return zone is too deep? Your return zone or your secondary curve. If that lens is too deep, you’ll actually see that lens riding up. Okay? So you’ll see here — for example, we have a really large area of central touch zone, which indicates that this lens is effectively too flat, and that RZD is too shallow. I was talking about being deep, but I mean too shallow. So here we can see that this area here, the return zone depth, is 500, so it’s too close to the actual cornea. Okay? And the lens is riding up. Similar to regular GP lenses that tend to ride up when the lens is too flat. And so if we increase that RZD, we can then center that lens. So we’re increasing the RZD, and we’re bringing that lens — we’re decentering it more inferiorly, if you will. And then we have a return zone that’s too deep. So when you have too deep of a return zone, that means the sagittal height of that zone is too high. It indicates a steep fit. So in this case, what you want to do, you likely have an undertreatment of some sort, and you’ll know that by the vision. But what you want to do is you want to reduce that RZD. You want to bring the lens down, you want to bring the sagittal height down. If you have a 550RZD, you want to change it to 525. Those are the smallest increments you can change the RZD. It can go in 25 steps. And you want to change the peripheral angles. This zone is important for lens position and stability, like I spoke about, as well as good tear exchange. So if that zone is too steep, the landing zone is too high, the amount of paracentral clearance will actually increase while the peripheral clearance decreases. In cases like this, when you have a really, really thin edge lift here, you’ll also have very limited movement as well, so you want to go ahead and increase your edge lift and you want to decrease the landing zone angle, if you will. So the smaller the angle, it effectively means you have more edge lift, and you want to decrease that angle. And then if you have a larger angle, that indicates less edge lift, and you want to increase the LZA, this change can be made in 1 degree steps. And that will have an effective change of approximately 15 microns. All right. Poll question number four. Which one of the following is the most accurate and useful method to assess lens position during overnight wear? Endpoint visual acuity, endpoint refraction, in-office fluorescein pattern and lens assessment, or corneal topography? All right. So most of you answered — so we had a split, but the majority of you guys said corneal topography, and I would completely agree with that. Although all of these elements are important. But corneal topography is probably the best method to assess lens position during overnight wear. Okay? Good. All right. Our follow-up schedule. We tend to follow these patients very carefully. And so we don’t always do the one day in the AM. Ideally it is nice to bring the patient back wearing the lens in the morning, after you’ve dispensed it the day before. You’re checking for lens adhesion, making sure the lens isn’t plastered on the eye, and that it’s easily removable, so you’re the first one to actually remove the lens, so you can gauge how tight that fit is toward the end. But more often than not, I’m really seeing them at that 7 day mark. And then we follow up with them at the 14 day, one month, three month, and if things are going well, can six months, and then at the annual visit. I do tend to like to see my patients every six months, for their first one to two years, and then once they’re more comfortable, we can kind of push it back to an annual visit, annual assessments. At the follow-up visit, we check their uncorrected visual acuity. Remember that at day one, you won’t necessarily see their visual acuity at 20/20. It’s actually very, very unlikely that you’ll see their visual acuity at 20/20. But it should be improved from baseline. Okay? And then moving to day seven, it should be getting even better. By day 14, we expect that visual acuity to be right on target at 20/20. And then we take a good history, we ask them what solutions they’re using for cleaning, even though we recommended these to them specifically, sometimes they don’t always follow our instructions, so it’s important to get a gauge of what they’re actually using. Get an understanding of the topography. So we do another topography here, we do a subjective refraction, to check for the amount of residual prescription left, biomicroscopy, without the lens, so we first look at the cornea, check for any staining patterns, make sure that the corneal physiology looks adequate. And then we apply the lenses. We check vision corrected. And that should be 20/20 in each eye. And you want to overrefract these lenses. You want to use loose lenses to overrefract and assess the contact lens fit. We do add fluorescein when we’re assessing the contact lens fit, to make sure that we’re getting that good bull’s eye pattern. When we’re taking a look at the topography, this is kind of what we’re looking for. Another bull’s eye pattern in terms of the topographical measurements. We want a central area of flattening, midperipheral area of steepening, which is denoted by the red here, and then peripheral flattening. So again, perhaps the most useful tool, when we’re determining efficacy: It’s my go-to when I’m looking at it. I trust the topography more than I trust what the lens actually looks like when I’m assessing it in-office. This is the best way to infer what the lens position looks like during nighttime wear, as we discussed already. All right. Let’s go to poll five. Which one of the following statements regarding myopic correction with overnight OrthoK is false? Low amounts of myopia are easily corrected? Patients with higher refractive errors are more likely to attain full correction? Patients with steeper baseline readings tend to have better results? And patients with higher corneal… Oh, I didn’t — skip that last one! We didn’t get to that one. So we have three options. So we’re asking which one is false. Yeah. Good. Yeah. So you guys got it right on the money here. Patients with higher refractive errors are more likely to attain full correction. That’s false. The higher the refractive error, the more difficulty in gaining appropriate vision here. All right. So some troubleshooting here. If you see a central island, which tends to be very common, especially initially — we usually see it within the first week, for sure — I usually don’t do anything at the first week. I wait until the second week. If that central island is still persistent, I then go ahead and make some changes to their return zone. So the central island is essentially this area here. You’re seeing this whole zone should be flat. You should see kind of a green pattern here. But sometimes you end up seeing this area of central steepening. That’s what we call a central island that shows up in the topography. It’s harder to see in an actual lens assessment. I actually pick it up more on a topographical image. It is essentially a steep lens. What you want to do is decrease the return zone, reduce the RZD, sometimes flattening the peripheral zone can also help as well, and you’ll also notice that these patients have a large residual refraction. During the first week, like I said, when I see these, I kind of just wait it out until the second week, and that’s really when I start to make these changes. Lateral decentration. This again is very, very common. More common when we see against the rule astigmatism or a smaller diameter lens. So I tend to actually be very vigilant about choosing my initial diameter. I’m a stickler for lens centration. I think that’s the best way to get a good proper fitting orthokeratology, is to really pay attention to the diameter of the lens that you’re choosing. But easy enough if you do see lateral decentration. You can increase the lens diameter. And making sure it’s about 90% of the HVID here. Vertical decentration. When you see vertical decentration, especially if that lens is decentered superiorly, you have a flat fitting lens. The lens usually needs a larger RZD in that manner. Or larger LZA to steepen the lens and bring it back down towards the center of the cornea. So a flat fitting lens has a low sagittal depth. Sometimes these are more commonly seen with — with the rule astigmatism. And on topography, we call this a “smiley face” topography, where that treatment zone or treatment curve or reverse curve isn’t fully complete, and it looks like a smiley face on the actual topography. So we would in this case increase the return zone or steepen the peripheral curve. Increase the LZA. And then the inferior decentration lenses are too steep. This is a reverse smiley face or a frowny face. We want to decrease the return zone depth, flatten the peripheral curve, increase the LZA. And a quick note about toric orthokeratology. I would say probably about 80% of the time, I’m actually fitting toric orthokeratology. And so with the Paragon design, there’s two curvatures. For the reverse curve. The base curve is still consistently 1. But then you have two curves here. For your return curve. And sometimes two curves for your landing zone as well. Depending on how that looks. So I find with any patient that has more than 0.75 diopters of corneal astigmatism, I need a toric OrthoK to achieve proper centration and proper stability. Otherwise, that lens rocks in its place, that patient gets a lot of induced astigmatism, they have decreased visual acuity, they have just decreased vision in general. They also complain of a lot of glare, halos, and shadows, and things like that. So when we’re looking at the topography, again, if you see that there’s about 0.75 diopters of corneal astigmatism, I would encourage you to just try a toric orthokeratology lens. If you see more limbus to limbus astigmatism, again, go ahead and try your toric OrthoK design. So when we’re looking at the cornea, at each follow-up, it’s very, very important to make sure that the lens isn’t bound to the cornea. So look for signs where the patient might have a lot of SPK or areas of corneal abrasion. I actually just recently had a 7-year-old girl, who I noticed a tiny little corneal abrasion at her six month follow-up, and I hadn’t seen that at all, throughout the rest of her follow-up periods. And I asked mom what was happening. She said they were forgetting to put in drops before they were taking the lens out. And that was causing that lens to adhere onto the central cornea, and when they were taking the lens off, they were getting something like this. Here’s a small abrasion, as they were trying to remove the lens. You also want to at this point rule out any infection. Infiltrates, ulcers, microbial keratitis. Iron rings are very common, especially if the patient has been wearing the lens for at least over a year. We start to see — similar to what we call a Hudson-Stahli line. It’s a very benign finding. We don’t necessarily do anything about it, but it is something that we like to note in our chart. The iron ring is just from the tears pooling in those areas. All right. I’m gonna skip this poll question actually in the interests of time. And we’ll move on to our last slide here on cleaning and care. I like to use the hydrogen peroxide system to clean the lenses. ClearCare is something available here in the United States that we like to use a lot. You can use other types of multipurpose solutions like Boston advance, the two step, or multipurpose solutions like Simplus and the Unique pH. Again, no tap water at all. And I do have them use a viscous non-preserved artificial tears for insertion. And I like to have them use a same Celluvisc or viscous non-preserved solution for removal as well. So this is kind of my go-to for cleaning and care. It’s seemed to work out pretty well. And with that, that brings me to the end of the presentation. I’m gonna quickly take a glance at the Q and A and see how many questions I can answer, just in the interests of time here. So let me get that Q and A. So one of the questions is: Which fitting method do I prefer? Do I prefer fitting empirically or diagnostically? I actually prefer to fit empirically. I find that it’s a lot easier. It’s quicker for me. I can just order the lens. Like I said, 90% of the time, those lenses fit really, really well. So I don’t have to worry about reordering the lens right away. Diagnostically, it just takes a little bit longer. Takes longer in-office. So I tend to kind of skip that. The only way I’ll do it is if that patient is really, really eager to start the treatment right away, or had it in their head that they were gonna start right away. And in that case, I’ll actually dispense the lenses right out of my fitting kit. I’ll actually give to them to take home. So that’s the only way I’ll actually fit diagnostically, is if I have the intent to give the lenses to them, to dispense it to them. I’m skipping some of these that I’ve already kind of answered within the talk. One of the questions here is — can we fit OrthoK with a patient with nystagmus? I haven’t actually fit a patient with nystagmus, likely because they tend to have higher amounts of refractive error that are beyond the parameters anyways, of what’s FDA approved and what we can do. And then their visual acuity isn’t so good either. So I tend to not. You have an unclear endpoint. I’ve never had the opportunity to fit any patient with nystagmus. I’ve never had that patient come in asking for it. I haven’t thought about it. I fit them with GPs quite a bit, I fit them with scleral lenses quite a bit. Because when the lens moves with their eye movement, it helps for their vision. But I haven’t actually fit anyone with nystagmus. I don’t know if I would. So the material and design with RGP… Great question here. So the lens actually tends to be higher Dk. We actually choose the highest Dk available from the manufacturers. Because the patient is wearing these overnight, so we want to make sure we’ve giving them as much oxygen permeability as we possibly can. So we tend to not use the same material. So I wouldn’t use a Boston ES. That’s a little bit of a lower Dk than a Metacon Z, for example, or a lens that has… I think we use the Paragon lens material, which is Dk of over 100. So we want to use a hyper-Dk, anything over 100. And yes, you can fit a patient — OrthoK for anisometropia. If it’s a fairly reasonable amount, totally, you can fit these patients with OrthoK. I’m trying to get one more question. Answered. A couple more questions answered here. So the adverse reactions that I’ve seen with orthokeratology — I have seen my fair share of corneal abrasions. And so I tend to be very careful about lens binding in these patients. I’ve seen patients develop very low amounts of keratitis. Not necessarily infectious keratitis. But maybe even mechanical keratitis, where if I fit the lens too flat or the RZD or return zone is too flat, they tend to get areas of SPK or superficial punctate keratitis in those areas. So those are — that’s the extent that I’ve seen as far as adverse reactions. I haven’t seen any infectious things yet. Thankfully. So I haven’t seen any infectious keratitis, microbial keratitis, corneal ulcers, because of OrthoK. So the question here is: How long should the OrthoK be removed before corneal topography is back to its normal condition, before one would go to corneal refractive surgery? That’s a good question, and something we run into quite often. Before I started at my practice, we had a lot of — the provider before me had been doing OrthoK. So I have a lot of adults now that are doing OrthoK, and a lot of them have asked about refractive surgery. So what we’ve done is actually weaned them off of their OrthoK, getting them ready for corneal refractive surgery. The estimate I would give you is: For every decade that they’ve worn the OrthoK, I would take them off one month. So most of the patients have been wearing them for about ten to twenty years. And so if they’ve been wearing them for up to 20 years, I make sure that I don’t have a lens on for two months. But I follow their topography. So we follow the topography almost on a biweekly basis and make sure it’s returning back to what we think baseline would be. Once we start to get two or three serial topography measurements that are the same, and look like a prolate cornea, that’s when we know we have our endpoint. So the question here is: Can OrthoK lenses be fit to correct hyperopia? The answer is yes. You can do OrthoK for hyperopia. I actually don’t do it. I have very limited experience with doing it. But it can be done. In this case, you would have a curvature in the center that’s actually steeper. And you would have to play around with the reverse geometry of the midperipheral zone to adjust those parameters to get your hyperopic correction. Just looking for one last question to answer. So what is the kind of pain or discomfort a patient might feel with OrthoK lenses? So actually… I described this already, but an eyelash. So that’s the best way that I like to explain it to my patient before I put the lens in. It actually feels like you have an eyelash stuck in the eye. So every time you blink, you’re aware of the lens movement. But as the patients wear it more and more, they tend to get more comfortable with the lenses. Do I recommend anesthesia? So the very first time we put the lens on, we’ll use a local anesthetic such as proparacaine in the cornea before we put the lens on, and that’s just to stop reflex tearing. If you don’t put any anesthetic, you end up getting a lot of reflex tearing. That can affect the way the lens looks on the eye. And also to give the patient a good impression of the lens right away. Knowing that they’ll eventually not like it as much. But initially, you can kind of gain their trust, in a way, and so over time, they’ll start to feel the lenses more and more, but initially, you can start to put the lens on with the anesthetic. And then eventually by the time you’re done with your assessment, they’ll start to feel the lens, but it won’t be as intense. I don’t let the patients take anesthetic home ever. So it is something that they have to eventually get used to. So with that, I’m gonna try to answer some of these questions later on, via email or what-not. If you have any other questions, I do want to do a follow-up to this, more advanced — maybe even bringing in some myopia control elements to it. But thanks, everyone, for your time. It’s been a pleasure to be here again. Yeah.

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February 4, 2021

Last Updated: October 31, 2022

2 thoughts on “Lecture: Introduction to Orthokeratology”

  1. Good informative video.
    Please share your experience of monitoring of Ortho-K related corneal changes through epithelial topography pattern only. As, I think epithelial topography would give more accurate presentation of changes in corneal reshaping, as the ortho-K theory based on epithelial cell migration.


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