Lecture: My Experience in Selection and Management of K-Pro in International Patients

This webinar discusses preoperative evaluation of patients undergoing K-Pro implantation, including indications, patient selection and preoperative testing. It also discusses postoperative management specifically focused on international patients, including infectious prophylaxis and the prevention and management of other common postoperative complications.

Lecturer: Soledad Cortina, MD, Associate Professor of Ophthalmology and Visual Sciences, University of Illinois Eye & Ear Infirmary, Chicago, USA


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DR CORTINA: Good morning. I hope everyone can hear me. I am Soledad Cortina, and I’m gonna talk to you today specifically about the Boston type I keratoprosthesis, and how we can select patients and manage them, focusing on the international patient. So if you have any questions, we’re gonna have some questions and answers at the end, and feel free to just send us those questions. I have no financial interest in this topic today. So why do we need an artificial cornea? What is the problem? So we know that worldwide there’s an estimated almost 5 million people that are bilaterally blind. That means that they have worse than 20/400 vision in their very best eye. These unfortunately include 1.5 million children. And the truth is that traditional keratoplasty has only a modest impact in corneal blindness. If you think about the numbers, there’s only 180,000 transplants performed worldwide and that would have little impact in these 5 million people. And about half of those transplants are performed in the United States. So there’s a shortage of donor corneas, be it for cultural reasons, administrative reasons, financial reasons. We are estimating that there’s close to 13 million people awaiting a corneal transplant in one eye. And only 240,000 corneas are recovered, and over half of those recoveries are performed in the United States and India, combined. So the truth is that 53% of the world’s population has no access to corneal transplantation. And even when they do have access, there’s a high failure rate of keratoplasty for high risk indications. So in the majority of blind people from corneal disease, penetrating keratoplasty is not even tried. So these are statistics from 2008, but I think it highlights how many countries like China, for example, in which the wait list for a corneal transplant is really, really large. Why do we need to do corneal transplantation? These are the indications according to countries. We see that the majority of the developed world is Fuchs dystrophy, followed by keratoconus, and the tropical keratitis in underdeveloped countries. And this is from a global survey published in 2016 in the Journal of Ophthalmology. The size of the countries means the prevalence of corneal blindness, and then the colors are color coded, as to how ready these countries are for corneal transplantation programs, and we can see that the largest country with corneal blindness that is the most ready would be India. And then from this same paper, this global survey, this one shows where the corneas are coming from, and which countries have actually been able to procure corneas, and we see that there’s only the United States, maybe Italy, that are exporters. So they ship corneas across the world. There are some countries that are self-sufficient or almost self-sufficient, and then there’s a large number of countries that are not sufficient, or really that there’s no cornea recovery, like many countries in Africa, for example. But say that we do have corneas. We know that corneal transplantation is the most successful solid organ donor transplant in the human body. So we have 80% survival rate of five years, in low risk grafts. But if we look at high risk grafts, those patients with autoimmune diseases, chemical burns, with significant corneal neovascularization, limbal stem cell deficiency, even glaucoma, the survival rate is between 25% and 0 at five years. So really the success rate goes down. So these are the three most commonly used keratoprostheses in the world. There are two broad categories. We call them type I K-Pros and type II K-Pros. On the type I K-Pro, used on a wet ocular surface, which means an eye that is able to blink, that has tear production, the most commonly used is the Boston type I K-Pro. Under some iterations of this device, like the Lucia and the Aura K-Pro, that is manufactured in India, but they’re all derived from this device — from the design of this device. And then for those patients with very dry ocular surface, surface keratinization, like patients with ocular cicatricial pemphigoid or Stevens-Johnson, severe chemical burns, we use the osteo-odonto- keratoprosthesis, which you see on the right side of the screen, or the Boston type II keratoprosthesis, which has a longer stem and goes through the eyelid. So today on this webinar we’re gonna focus on type I. We’re gonna focus on those eyes that have the ability to blink and have a relatively moist surface. So this is our first question here. And it’s: Which of these patients is the best candidate for a type I keratoprosthesis? And you have four photographs here, and we’re gonna give you some time to answer. All right, very good. Looks like the majority picked B. That is correct. For a type I keratoprosthesis, A is symblepharon. This patient is not a candidate with how the eye is looking right now. C and D need further work before we can think about implanting. However, B is a perfect candidate for a type I keratoprosthesis. So the Boston type I keratoprosthesis was designed by Claes Dohlman, and it was approved in the United States in 1992, and it’s indicated for those patients that have a poor prognosis for penetrating keratoplasty. What is the device like? It’s a collar button design, the optic is made of PMMA, the peak plate locks into place with a titanium ring and I’ll show you a photo of that. Ten years ago, the use of keratoprosthesis was really limited. The complications were really high, high infection rate, high incidence of extrusion, but in the past decade or so, maybe 15 years or so, it has shown improved device design, improved postoperative management in these patients, reduction of complications, and really it’s a lot more accepted by corneal surgeons worldwide. To the point that now it is really considered the preferred option for those patients that have a poor prognosis for keratoplasty. And over 12,000 keratoprostheses have been implanted worldwide. And we’re talking again about the type I. Why did we see these improved outcomes? Well, the design changed. Holes were introduced in the backplate that decreased the rate of melting of the carrier tissue. We identified prognostic categories, how to select patients better, for which we were implanting these devices. We started using prophylactic antibiotics to decrease the rate of endophthalmitis, and introduced a bandage contact lens, used to improve the hydration of the tissue. Protection of the ocular surface, and decrease the rate of melting. So the only K-Pro design that you can see here had a 51% rate of melt, because it had a solid backplate, and we thought that not enough nutrients were reaching the carrier transplant from the aqueous humor. So now 8 backplate holes were introduced, as you can see in this picture right here, the difference and the rate of melt decreased to around 10%. So the new design introduced titanium backplate, with a C locking design, so this doesn’t use a ring anymore. And this is the old model, that is still available, where you can lock it with that titanium ring. The advantages of the titanium backplate is that it has a cleaner profile, so the anterior chamber is less crowded. So something important that we’ve found is that really the use of the Boston keratoprosthesis has a significant impact in the vision-related quality of life, so we did a survey, and we asked these patients before and after implantation, and their vision-related quality of life by the survey improved significantly. So who is really a candidate for a keratoprosthesis? This is what we want to discuss today. Well, as with any other surgery that you do, of course indication is one of the most important aspects of the success of your surgery. So selecting the right patient for the right procedure. So this is our question number two. And it’s: Which indication is considered to have the worst prognosis in keratoprosthesis? And this is in general. I’m sorry. I think the answer came up on its own. Sorry about that. I’ll wait for the results anyway. And yeah, so I think the very best prognosis are those patients just with non-inflammatory conditions, like multiple failed grafts. I think aniridia has a guarded prognosis in general, because of the syndrome and fibrosis, and glaucoma and everything else, but in general is a good candidate for keratoprosthesis. Chemical burn, it can be quite severe, and depends on the degree of chemical burn, but by far Stevens-Johnson syndrome, with an autoimmune etiology, has the worst prognosis. So indications for Boston type I K-Pro: Repeat corneal graft failure, any etiology for limbal stem cell deficiency, burns, SJS, aniridia, a neovascularized cornea with poor prognosis, any neurotrophic keratopathy can be good candidates for Boston type I K-Pro. And here in this table you can see how we group the prognostic categories. So our good prognosis, anything that is not inflammatory. Intermediate prognosis is — there is some inflammation, history of infection, chemical burns. Herpetic keratitis, or neurotrophic keratitis. And aniridia. I place aniridia here, because it’s a little more complicated than just repeat graft failure for keratoconus, say. And all the autoimmune conditions like Stevens-Johnson syndrome and cicatricial pemphigoid are the worst prognosis. So which of the following is a contraindication for keratoprosthesis implantation? And this is our third question. I’ll give you some time to answer. Good. So yes, I think uncontrolled inflammation is a contraindication for a keratoprosthesis implantation. You should not implant them when there’s active inflammation, because your results are gonna be bad. The tissue is going to melt. They’re gonna have many complications. So do everything that you can to control the inflammation. If it’s topical medications, systemic immunosuppression, whatever you need, but the inflammation needs to be controlled before you implant. Aphakia actually — it is not. And I prefer to implant the keratoprosthesis when the patient is aphakic, because I think there’s less crowding in the anterior chamber. I think we do need some tear production. So Schirmer’s test — a good Schirmer’s test is a good indication. And neovascularization is actually one of the indications. That’s why we do it. We know that PKP will have high rejection rate, and that’s why we do the keratoprosthesis. So there’s three key features that I want you to think about when you’re examining a patient and thinking about a K-Pro. Number one is a moist ocular surface. So it doesn’t have to be a Schirmer’s of 10, at 10 minutes or what-not. But there has to be some tear production. If there’s keratinization, it’s a bone dry surface, the type I is gonna do very poorly. Fornices that can accommodate a contact lens. So if there is significant symblepharon in this eye and they cannot have a contact lens, then the tissue may desiccate. So you may think about reconstructing these patients first, before you venture into the keratoprosthesis. So significant symblepharon is something that you want to stay away from. And then you want to have, again, controlled ocular surface inflammation. So think — not the worst case in your practice is the best candidate for a keratoprosthesis. Because when we think about this procedure and we think about artificial cornea, the very worst case you have, you think this is the one I’m gonna implant the K-Pro on. But if you look at this person here, with Stevens-Johnson syndrome, completely keratinized, and ankyloblepharon, this is not a candidate. This needs osteo-odonto-prosthesis. You can see this patient — the fornices are okay. There’s some tear lakes, tear production. So this patient would be okay for a type I. Same with this patient who has aniridia. This is also a good patient for a type I. This patient right here, you know, very poor eyelids. There’s ocular surface inflammation. This would be a more guarded — and I would definitely not do your first K-Pro in a patient like that. And of course, the multiple failed grafts, history of multiple rejections, is kind of the best candidate to start implanting K-Pro. So we use it for repeat corneal graft failure. It’s an acceptable alternative. The visual rehabilitation is faster, we don’t depend on immunosuppression therapy, so this is a good indication. For corneal dystrophies that are highly recurrent, for example, this patient that had gelatinous corneal dystrophy, like an amyloid dystrophy, she had 17 lamellar keratoplasties before we did a K-Pro, and it kept recurring and recurring. And you can see the degree of vascularization — a penetrating keratoplasty would never work in her. So these patients are good candidates for a type I. Remember not all of your million patients are a good candidate for a type I. With every disease, there’s a spectrum. So those patients with Stevens-Johnson syndrome, for example, that have a wet ocular surface, that have very controlled inflammation, that there’s no active disease, those patients are a candidate for K-Pro. Never, never, never in the active disease state. For limbal stem cell deficiency, including aniridia, I think it’s a very good indication. Don’t forget, though, that your persistent epithelial defects and corneal melts may have higher incidence in these patients, and aniridics tend to have a higher incidence of retroprosthetic membranes, maybe because of their tendency to fibrosis. In severe ocular trauma, in particular ocular burns, I think it’s a good indication. But please don’t forget about glaucoma. This is a huge issue in patients with chemical burns, with or without keratoprosthesis, and can significantly worsen after keratoprosthesis implantation. So always think about how you’re gonna manage glaucoma in this patient. Think that stabilization of the ocular surface first is always necessary. So don’t rush into the K-Pro. Sometimes we’re in a rush to rehabilitate these patients visually. Especially when their injuries are bilateral. But to have a stable ocular surface is key, before we move into keratoprosthesis surgery. Like we talked before, for herpetic or neurotrophic disease, it is not a contraindication, like some other versions, other types of keratoprosthesis were, like the AlphaCor. So this is actually a good indication. But the prognosis for those patients with HSV keratitis, for example, or herpetic keratitis, is not as good. So we have them on our intermediate prognostic category. Pediatric corneal disease. This is a group we would love to have a keratoprosthesis that works. In very young patients or babies with congenital anomalies, the transplants don’t work well, and the risk of amblyopia, even with a clear transplant, is significant. But the truth is that keratoprosthesis are very high risk in this group of patients, and there’s more evidence to suggest that the outcomes are poor. So I would say stay away in very young patients, and perhaps in my own experience, patients that you can bridge them with a corneal transplant, develop their vision, and maybe after the age of 10 or so, they respond much more differently to the keratoprosthesis, and they can have a much better outcome. It can be as a primary penetrating procedure. So you don’t need to have patients — you don’t need a failed transplant to put a keratoprosthesis. If you already think that this patient had a poor prognosis for PK, for example, the cornea is completely vascularized, or they have limbal stem cell deficiency, you know that a penetrating keratoplasty alone, without a limbal stem cell transplant, for example, will not work, so these patients can have a primary keratoprosthesis. And then another good indication is those patients that have hypotony, or retinal disease with silicone in the eye, and they have recurrent keratopathy from the silicone oil, they can have good outcome with a keratoprosthesis. So how are we gonna evaluate these patients? How are we gonna plan surgery? So of course, like you do for any other surgery, a thorough history. You want to estimate the visual potential. Because most of the times you cannot see in the back of the eye. You don’t know the retinal status except for ultrasound, to make sure it’s anatomically in place, but we don’t know functionally. Same thing we don’t know status of the optic nerve. So we like to get an idea of what the vision was like after their last transplant, history of glaucoma before, to make sure if we do a keratoprosthesis, we’re gonna get some improvement, and we’re not gonna implant a device with no improvement in vision for these patients. Think that maybe a decent candidate can be a better one. This patient with chemical burn, significant symblepharon, we’re gonna decide: Let’s reconstruct the symblepharon, do a buccal mucosal graft in the eyelid, make the surface better before we implant the keratoprosthesis. You can assess with amniotic membrane or mucous membrane graft and consider the need for immunosuppression. Look at the eyelid. It’s important that we address eyelid abnormalities, if not before the surgery, immediately afterwards. Tarsorrhaphy are your friends. If you want to do a bilateral tarsorrhaphy a third of the way, that gives protection of the ocular surface and can improve the outcome for keratoprosthesis in some patients. Always look at the eyelids and make sure there are not significant abnormalities that need to be addressed. You’re gonna do — before the surgery, think about imaging these patients. You can do an ultrasound UBM. You can do anterior segment OCT. To get an idea of what to expect inside the anterior chamber, do I have an ACIOL, PCIOL, crystalline lens? Is the patient pseudophakic? Am I gonna keep the intraocular lens, or am I gonna remove it? Anterior chamber lenses need to go. Posterior chamber lenses in the bag that are stable you may decide to leave in place. And that’s why you have two models of the type I keratoprosthesis. One for aphakic patients and one for pseudophakic patients. And then also anterior segment imaging can give you an idea: What’s going on with the iris? Do I have a normal iris? Do I have synechiae? And what to expect when you open these eyes. And these are just some examples of iris adhesions, peripheral anterior synechiae, and in this one here, you can see how the IOL looks nice and stable in the back. So you can look if these patients have had glaucoma, where is the shunt located. Am I gonna need to reposition it? Because it’s gonna interfere with my keratoprosthesis or not. Also, you’re gonna do an A-scan, or an axial length measurement, because if you’re gonna go with the aphakic model, you’re gonna need to provide the axial length to be able to order these keratoprostheses, or at least have an idea. Now, some of the lower cost keratoprostheses that are the same model as the Boston type I, they come only for one axial length, and then the residual refractive error you would correct with a bandage contact lens. You always want to do a posterior ultrasound to make sure there’s no gross posterior segment pathology that you need to know about. Surgical planning also needs to include glaucoma. Because this is really the main cause of permanent vision loss after we implant a K-Pro. Everyone with preexisting glaucoma and on medications will get a shunt in my book. Everybody will get a shunt at the time of K-Pro. If somebody doesn’t have glaucoma, that’s still controversial, and you may decide to still put a shunt, depending on what the pressure is. And I’m leaning towards this option in many of my patients. And then think about the role of Diode, if the patient has had many shunts before, there’s no room for a shunt, no good conjunctiva for a shunt, Diode can be useful sometimes. What are the considerations about glaucoma implants? Things that we have to think about? Well, there’s gonna be a crowded anterior chamber because we’re gonna have the backplate inside the anterior chamber. The iris. Many of these patients with conjunctival surface disease can have scarring. You think you have to fit them with a contact lens, and you don’t want a bulky plate rubbing against the contact lens, causing conjunctival erosion or exposure. And you can see in these photographs some of the complications. Because of poor contact lens fitting due to the shunt, exposure of pars plana, and exposure of the shunt. So what do we do? We have developed this technique where we place the shunt in the pars plana. It asks for more surgery, because now we need to do a pars plana vitrectomy in those patients that have not been previously vitrectomized, but you can see how nicely you can fit a large contour lens with a very nice and flat profile. The shunt has much less risk of exposure. And here is an anterior segment OCT, showing the entrance of the shunt. It’s about 4 millimeters posterior to the limbus. So this is the keratoprosthesis. This is how we construct it. For surgery. There’s a small adhesive that you can place the front plate on. Or you can just use a little bit of viscoelastic to give it some hold. You’re gonna pretrephine the graft. I usually use 8.5 millimeters for the graft. You can use 9, just to be bigger than the backplate. And then there’s a derm punch that comes with a kit, and we’re gonna trephine the center of the graft. It is 3 millimeters, and you thread that through the optic. And then you’re gonna put the backplate. You can push the backplate with this hollow white pin. It also comes with a kit. And then you’re gonna place the titanium locking ring over the stem. I usually just at this point push with my index finger to try to have it in place, and then with a hollow pin, you finish pushing it in, and you want to hear this snap, that it goes into the groove, and then you want to inspect your keratoprosthesis 360 degrees, and make sure that the titanium locking ring doesn’t have the arms, one higher than the other, that everything is in the groove, and that the stem is protruding the same amount, 360 degrees around. If you’re using the model with the titanium backplate, that has a C-shaped titanium backplate, the same thing. You want to inspect it all around. Make sure that the backplate is level and that one arm of the backplate isn’t higher than the other. So this is our technique. And I’m gonna run you… We call it the triple K-Pro procedure. Because we’re gonna do first the shunt. You can use an Ahmed, or you can use a Baerveldt. A lot of these patients are on oral Diamox or acetazolamide, and then if you do an Ahmed, then you don’t have a problem with this. So we usually just put the plate before we open the eye. And then we’re gonna tuck the shunt in. We’re gonna trephine and open the cornea. My retinal specialist likes to do the vitrectomy through a temporary keratoprosthesis. So we suture this now. The vitrectomy can be performed through the permanent keratoprosthesis. It’s just difficult to get that far out, because the opening is less. Of course, with a temporary keratoprosthesis, it’s very easy to clean the vitreous in the periphery and make sure that where the shunt goes in, there won’t be any vitreous clogging the shunt in the future. So like I said, it’s about 4 millimeters posterior to the limbus. We enter, and we’re gonna make sure that the entry point is where we want it. That we’re not going through retina. That it’s in the pars plana. And we’re gonna insert the shunt in this area. And after this, we will close over the shunt. We will close over the shunt and put the permanent keratoprosthesis. You can see here that I’m using a backplate that is smaller. You have two options for backplates. It’s an 8.5 millimeter and a 7 millimeter backplate. So here I’m using a PMMA 7 millimeter backplate. It’s considered the pediatric backplate, but I really like it, because it’s easier to suture. And it’s less crowded inside the anterior chamber. We use the patient’s own cornea to cover the shunt in this case. You can use cryopreserved corneal tissue as well, but it saves some resources, and you can use the patient’s own cornea. That works pretty well too. And this allows to see the shunt under the tissue. So now we’re closed and this is the end of the surgery. We’re gonna place the contour lens. This also comes in the kit with the keratoprosthesis, and the standard lens that we use is the 8.9 — 9.8, 16-millimeter. At least for the starting point. So how do we care postoperatively for these patients? So it is labor-intensive. The type I patients are the patients that are gonna need frequent follow-up. Patient education is key, and an interdisciplinary approach is also very important. Because these patients will have a complication at some point, and to be able to have on your team — if you’re a cornea specialist, to have a glaucoma specialist that can help you, somebody to fix the eyelids from oculoplastics, if you don’t do that, contact lenses, and retina, is very important. So question number four. I’ll give you some time to answer. Is: How often should I examine my K-Pro patients? All right. Every three months. Fantastic. Yes, that is the correct answer. Because there are many complications that can happen, that are asymptomatic. So when the patients are doing great, totally stable, they see you every three months. If they have a problem, of course, you may see them sooner, depending on what that is. But at least every three months for those patients, because corneal melts can develop asymptomatically. And you might be able to catch them. They can have infiltrates around the stem without any symptoms, colonization, so every three months is the right answer. So what do we do for follow-up care? We see them every three months after the initial postop period, of course. Tell them to avoid eye rubbing. You’re gonna encourage compliance with a treatment specifically with antibiotic prophylaxis, because they stop the antibiotic prophylaxis, and they come back with an infection, more often than not. Inflammation control. Initially we use prednisolone acetate 1%, four to six times a day, and then we taper it, and leave it as needed. Some patients need one drop a day for as long as they have the K-Pro on, to keep that surface inflammation under control. We use a bandage contact lens. The initial lens we place is a Kontur 9.8/16. And then we fit it as needed. Some patients can use a regular contact lens that is not a Kontur, like a Night and Day, and those are okay. You can disinfect it at every visit, and most patients do not handle the lens, so when they come to see you, you remove the lens, you disinfect it, or you give them a new one, depending on how long they’ve been wearing that lens. Contact lenses can have some complications, for example, like deposits in this case here. They have a lot of deposits that are very frequent, you may want to move to a hybrid lens, which are those lenses that have a central rigid aspect, and then a soft part, a soft skirt, so the deposits can localize in the skirt, but at least the central part remains clear. And for those patients that can have significant glare with the K-Pro, or for cosmetic purposes, you can use tinted contact lenses that look very good as well, and can match the other eye. Infection prophylaxis is very important. You’re gonna adjust the prophylaxis depending on what the prevalence of infection is in your area. So what we use here in the United States might be different from what people use in India, or in China or in Europe. So it all depends on what the prevalence of infection in your area is. But vancomycin 15 milligrams per cc for high risk patients is what’s recommended, plus or minus a fluoroquinolone. Polytrim, which is a combination, can also be a good idea for low risk patients. If you don’t have good access to antibiotics, or you have high resistance rates in your area, perhaps Betadine 1% can be tolerated. Not by every patient, but by some patients. This is the recommendation by Mass Eye and Ear, for Boston type I K-Pro, for the non-autoimmune patients and for the autoimmune patients. Fungal prophylaxis. So you have a patient with poor ocular surface, that can be on chronic steroids and chronic antibiotic prophylaxis, and wear a contact lens. It’s like the perfect setup for a fungal infection, right? So you want to be very vigilant of this. If there’s high fungal infection rate in your area, you may consider fungus prophylaxis. Maybe once a month. Or every three months. And you can use amphotericin B or you can use natamycin. And just look for fungal colonization on the contact lens that might look like this. Monitoring for glaucoma. The intraocular pressure can be difficult to assess, but sometimes pneumotonometry over the sclera can be useful. You can do a Humphrey visual field, but I find that a Goldman visual field, especially for patients with lower vision, can be helpful as well. And visioning the optic nerve is important. All this visual information and imaging is from a K-Pro patient of mine. So you can get excellent imaging for these patients. Question number five. What is the most common cause of permanent vision loss after K-Pro? We went over this. Just testing if you’re paying attention. Exactly. So glaucoma. This is the most common cause of vision loss in general. Now, endophthalmitis is an important cause, and it looks like the audience did recognize that, because of the severity, because of the fulminant course it can have, but for patients who are compliant with their prophylaxis, thankfully the rate of endophthalmitis is much lower. Postoperative complications. So we can have infectious endophthalmitis at a rate of 2.5 to 5%. Glaucoma, new onset or progression of preexisting disease. Remember, the vast majority of these patients are gonna have glaucoma from before. So it’s not only the K-Pro causing the glaucoma, but it’s really the main cause of vision loss that we see overall. Sterile keratolysis, anywhere between 10% and 17%, infectious keratitis and retroprosthetic membranes, which is probably the most common complication. So which are the most common organisms causing endophthalmitis in K-Pro? This is question number 6. Gram positives. That is the correct answer. Now, acanthamoeba is rarely recognized in K-Pro. I know that these patients do wear a contact lens, and it can happen. Fungal is a significant organism. And Gram negatives as well, particularly because of the use of prophylaxis for Gram positives. Because most of the infections come from the ocular flora of this patient, and are Gram positive. So now that we’re giving vancomycin prophylaxis to cover Gram positives, then Gram negatives and fungal infections can rise, but still by and large Gram positives are the most common organisms. So risk factors: The K-Pro can provide a potential path for bacteria into the eye, because this is — particularly a keratoprosthesis, you know, all prosthetic devices in the body are at a risk for infection, but this prosthetic device has simultaneous contact with the outside world and the inside of the body, so that is why the risk is so high. A compromised ocular surface, local immunosuppression, the bandage contact lens, et cetera. But with the use of prophylaxis, the incidence of endophthalmitis decreased significantly. So that’s why we always have to encourage the use of prophylaxis in these patients. Infectious keratitis can be anywhere from 3 to 16%. May precede endophthalmitis. And we see that there’s almost like a 50/50 incidence for infectious keratitis between bacterial and fungal. So in the absence of a causative agent, negative cultures, on initial empirical treatment, you might consider treating for both, depending on how it’s looking. Glaucoma development or progression, like we talked. Leading cause of permanent vision loss. The mechanism is likely multifactorial, and we have difficulty assessing the IOP. Sometimes we may think the patient is doing fine, but really glaucoma is progressing. So that’s why we really need to be aggressive. We have shown that shunts reduce the risk of developing glaucoma or the risk of progression of glaucoma in K-Pro patients. We see how the angle closes over time. This is one of the factors why glaucoma develops or progresses after K-Pro. This is a patient, and you can follow from before the keratoprosthesis, you know, one month, three months, six months, how the angle kind of zippered and went into angle closure. So ideally you want to team up with a glaucoma specialist, who you want to treat IOP elevation at your lowest suspicion. You want to follow the angle with imaging if you can, because that can give you a clue as to what’s happening in the anterior chamber. You need to have a very low threshold for a shunt placement in these patients. And I think that sometimes IOP lowering drops can have a reduced effect, because of the decreased surface contact with the artificial cornea. And oral, of course, carbonic anhydrase inhibitors can have a role here as well. Retroprosthetic membranes is the most common complication. They can be significant, because they obscure the visual axis, but also because they can increase the risk of sterile corneal melt. And this is what we’ve shown, how retroprosthetic membranes can increase the risk of melt. We saw in patients that had the thicker membranes had the higher risk of melting. Risk factors for RPM are infectious keratitis and aniridia. These patients have more RPM than other patients. Steroids can help. Perioperatively, and then topical steroids can help decrease the severity, or any sort of immunosuppression, for that matter. So you can use anterior segment OCT to measure these membranes. And here you can see an anterior segment OCT on somebody without a membrane, a very little membrane that’s kind of growing, and then a thick membrane here. So the treatment would be with laser. And it’s pretty easy to do. If it’s very thick, you may need to do pars plana vitrectomy or a K-Pro exchange. Thinning, melting, and extrusion. It did decrease with the implementation of the backplate holes and the contact lens, and the retention today for the type I K-Pro is very high, from 80% to 95%. But a very thick RPM is a risk factor. Surface inflammation and epithelial defects are risk factors. Contact lens loss is another risk factor. And of course, eyelid abnormalities that cause exposure are also risk factors. So here you can see an explanted keratoprosthesis, and we’re peeling the retroprosthetic membrane from the back. And you can see how thick that membrane is. It’s almost like another cornea. You can see the area here of the melt. The tissue coming up to the cylinder of the keratoprosthesis. So you’re gonna replace the K-Pro as soon as possible. Sometimes you can try to patch it. With different tissues. It could be with cornea, it could be with sclera. Sometimes some people in Spain use dura to cover the area of the melt, but what works the best is obviously to replace it if you can. You can use glue, if the melt is small. Cyanoacrylate glue. And you always want to address the risk factors so that it doesn’t recur. Luckily, if you treat it well, patients go back to their baseline vision, and this is actually a complication that we can successfully treat. So finishing up here, key things: You want to watch these patients closely. You want to remember that glaucoma can progress very rapidly, if the IOP is not controlled. These are not patients that progress like… The primary open-angle glaucoma patient. These patients progress fast. So if the IOP feels high to you, it is probably high, so do something. Make sure the patient understands the risk of infection, and knows to walk in the door with minor symptoms. So access of the patients to you or to a care center that can care for these complications is very important. If you implant a K-Pro and the patient goes seven hours away and can never come to see you, that’s probably not a good idea. Some complications may be asymptomatic, like sterile corneal melts. So that’s why routine frequent office visits have a big role. So in summary, key factors to improve success of your K-Pro surgery are a careful patient selection, prepare your patient for K-Pro implantation. Don’t rush into it. Think of things you can do to make the environment for the K-Pro better. Have a solid surgical plan. Don’t forget about glaucoma. Follow your patients closely. And diagnose and treat complications early. So thank you very much. And I think now we have some time for questions.>> Yes, thank you, Dr. Cortina. We have one question so far, if you want to stop sharing your screen.

DR CORTINA: Okay, stop sharing. Yes. So the question is: When do you replace bandage lenses? So the lenses can stay in place for a long time. Especially the Kontur lenses. So you can keep them in place — I usually keep them in place for about six months, and then I disinfect every time they come. For other lenses, like the Night and Day lenses that are meant for one month, I usually replace them every time they come, which is every three months. But I always disinfect every visit. And something that I’ve been doing now also is, when I’m disinfecting the lens, I may put a drop of 5% Betadine on the surface of the eye, then wash it, and put the lens back.

>> Great, thank you. That looked like the only question. So I’m just gonna share my screen quickly. We had some questions asked at the time of registration. Since we have some time, if you want to go through these.

DR CORTINA: Have you any experience of using K-Pro in CVS? I’m not sure what CVS is. I’ll move this away. So please let us know your best contact lens parameters for K-Pro patients, how much that costs for a patient, and is it compulsory to use contact lenses? Okay. So usually the Kontur is what is considered the best. And we start with the parameters that are 9.8 base curve, with 16 diameter lens. And then we adjust as needed. I would say that probably about 70% of patients will be just fine with this lens, and you’re not gonna have to change it, and then other patients that may have a very flat surface or a very irregular surface may need some adjustments. Is it compulsory, the use of contact lenses? One way you can get away from not using a contact lens if the patient has good conjunctiva, just don’t spoil it for the shunt, but you can do a Gunderson flap over it, to protect the cornea. Especially in those patients that lose the contact lens often, because there are patients that, no matter how many adjustments you make, they keep losing the contact lens very often. And then… Let’s see. Some patients might be okay without a lens. These are the minority. But one of the things that I look at, to decide whether I can keep them without the lens is sometimes you can see corneal epithelium growing over the K-Pro, and that kind of seals the area, the junction between the graft and the artificial cornea. And so then you can leave them without the lens pretty successfully. But I would follow them closely in the beginning when you’re leaving them without the lens. With K-Pro II available, what is your opinion regarding type I? Yeah, I think they have different indications. The type II is for very dry eyes and keratinized eyes or ankyloblepharon, and they have to be bilaterally blind, and the type I is for the wet ocular surface. So they’re asking me if I have any experience with computer vision syndrome in K-Pro, and the answer is no. I’ve never implanted for this indication. What is the age limit? So I think keratoprosthesis works very well for the old, for example, because you can rehabilitate them very quickly. I think for older people, it’s great. Like I discussed in my presentation, pediatric cases are very, very tough, and I think that the outcomes in very young kids are not good with this K-Pro. So I would stay away from it until at least they are — and this is my own experience — until at least they are around 10 years old. What would be the best vision that we can expect from a K-Pro patient? So it all depends on what their potential is. I have many patients that are 20/20. With an artificial cornea. If they have a normal retina and a normal optic nerve. So that is the nice thing about the K-Pro. You don’t have to worry about postoperative astigmatism. Now, is the quality of the vision as good as normal vision? Probably not, because they’re looking through this cylinder. There are some videos that I can share with you some other time, where we can estimate about… You know, what the vision is like. They do have some disability glare. And for this, a tinted contact lens can be helpful. But I think in terms of your Snellen visual acuity, if they have the potential, they can see 20/20. If a patient has good vision in one eye, would you consider doing a K-Pro in the other eye? I do, yes. But it all depends on what the reason for the disability in this eye is. I think that in general keratoprosthesis is better thought of when patients are bilaterally visually impaired. But if the patient is motivated, if they will have good access, they have one normal eye, and the other eye has a problem, and it’s not a candidate for a regular transplant, then yes, my answer is I will implant the type I K-Pro. But I would never implant a type II. The type II, those that go through the eyelids, or the osteo-odonto-keratoprosthesis, those are strictly for bilaterally blind patients. How much will the cost be in general? I think that all depends on where you’re from and where you live. Like I said, for example, in India, they are manufacturing something that is basically identical to the Boston keratoprosthesis, and it’s a much lower price, and they can use that. The only difference is that it doesn’t have all the axial lengths, and you have to correct the refractive error with a contact lens. I know that the Boston Mass Eye and Ear Infirmary, when they ship internationally for those countries that are in more need, they significantly discount the cost of the keratoprosthesis. And they are also trying these other keratoprostheses called the Lucia keratoprosthesis, which again is very similar to the type I, which is some small device modifications, and it’s a much lower price as well. The idea is they understand that we need a cheap keratoprosthesis that can reach everybody in the world. So the cost of the device would be one thing, and then one has to factor in the cost of the antibiotic prophylaxis that will be for life, as long as the patient has the K-Pro in place. And also the office, all the visits with you, the transportation that all of that requires has to be factored in, and then the potential for more surgery, if complications arise, or further treatment.

>> All right, Dr. Cortina. That looks like the final question. Maybe we’ll wait a couple more seconds to see if any last questions come in.

DR CORTINA: If you implant a K-Pro in a patient with a normal other eye, do they have anisoconia? My patients that are unilaterally implanted with good vision in the other eye have never complained of that, no. Have never complained of anisoconia. They may say that the quality of the vision is different between the eyes. They have never complained of that. Can we do laser peripheral iridotomy after a K-Pro? I think it is difficult. It is difficult. So I would recommend that you do a peripheral iridotomy at the time of K-Pro. I think that’s a better way to do it, just prophylactically. Then if the angle starts closing, there’s not much you can do after that. And you may have to think about putting a shunt, if you didn’t put a shunt at the time of K-Pro.


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July 23, 2018

Last Updated: October 31, 2022

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