Lecture: Minimally Invasive Glaucoma Surgery (MIGS)

In this lecture, Dr. Lewis talks about all the steps in Minimally Invasive Glaucoma Surgery (MIGS). He stresses upon the importance of adjusting the microscope for good visualization and shows a few surgical procedures. He discusses about the different types of stents and the importance of gonioscopy.

Lecturer: Dr. Richard Lewis, Sacramento, USA
Lecture location: on-board the Orbis Flying Eye Hospital in Addis Ababa, Ethiopia


(To translate please select your language to the right of this page)

DR LEWIS: I was asked to give a series of different talks, and there’s a lot of interest in microincisional glaucoma surgery, the MIGS world. Let’s start there. There’s always been a question about whether glaucoma should be a medical disease, treated with medications, or a surgical disease. If we had a perfect surgery, I think all of us would opt to have surgery first. If we had an operation that was perfectly effective, and had no complications. Now, up until the last few years, the glaucoma rate from glaucoma surgery was very high. And nobody would volunteer for glaucoma surgery unless they had no other options. But the world has changed. We’re now in the MIGs world. Microincisional surgery. Much smaller, much safer, and not quite as effective as trabeculectomy, but close. So perhaps we’re heading to a world where this will be a surgical disease. You know, eye drops cause a lot of problems themselves. In the US, where I am, patients are treated for many years with eye drops, and then they end up having problems with redness, conjunctivitis, changes like this, where you see this kind of redness. Which eye was being treated with medications and which eye had surgery? You think the left eye had the medications or the surgery? The patient’s left eye had medications. No question. Look at that. That’s the kind of redness you see with Latanoprost. You see that with Alphagan. The patient’s right eye had to have surgery. The eye looks very comfortable. The pressure is actually quite good. So it would be wonderful — and we’re heading in that direction, where this may become a surgical disease, and we’ll stop using medications. But for now, we’re still on medications. And in my next lecture, I’ll talk about what the current medications are in the US and what’s coming out next. There are some exciting things happening. So MIGs stands for minimally invasive glaucoma surgery. It’s ab interno, microincisional. Low risk. Earlier intervention. We can treat these patients much earlier. We don’t have to wait until the very end stage disease. Minimal additional technology. You can use your existing — your microscopes. You don’t have to buy expensive tools, like with other devices. It does not preclude other surgery. We can still do trabeculectomy or Ahmed implants or cyclophotocoagulation. Because all this is being done internally. We’re not scarring down the conjunctiva, like what happens with trabeculectomy. And it’s an evolving technology. When I was asked to come to Ethiopia, the original plan was to teach CyPass. And that’s a suprachoroidal device. I think it’s a very straightforward surgery. It would have been easy to teach. And it’s very effective. I’ve done over 100 cases in the United States. It’s an exciting technology. Unfortunately, as many of you know, Alcon, which manufacturers the CyPass, did a five-year study. Began to show problems in the endothelium of some of the patients with CyPass that had to do with placement of the tube. And they temporarily have withdrawn that from the market. And once they pulled it off the market, it was pulled off the market all over the world, even though it was mainly being used in the US. So in the short term, we can’t use CyPass anywhere. But I said… Well, I’d still like to come and teach these other MIGs techniques, because the principles of MIGs technology is the same. You still have to position the patient and their head in a certain way, you have to position the microscope in a certain way, which I want to go over. And they still have to be able to understand the anatomy of the anterior chamber. And that’s what I want to talk about today. So how do you do it? Well, I just said the visualization is crucial. You need the head and microscope tilt. You have to be very comfortable using a gonioprism in your non-dominant hand. How many people have used a gonioprism in surgery? Anybody? One, two? It’s not easy, at first. It’s challenging. And what I’d encourage you — anybody who’s interested in doing MIGs — is to get a gonioprism, and after you’ve completed your cataract surgery, but the eye is still open, so to speak, you take your gonioprism, put it on the eye, rotate the head, as I’ll show you, and practice. And practice using the Sinskey hook inside the eye, hitting certain targets, so you get comfortable with that technology. Before you do any of the MIGs procedures. And then as you do a MIGs procedure, it’ll be a lot easier. So you have to get comfortable. You have to get good visualization. And you have to practice, using these instruments in the eye. So optimal visualization — and we’re gonna do one of these this afternoon. We have a MIGs case coming up to follow this cataract. And you’re gonna see what I’m gonna do, after I take the cataract, do the cataract surgery, is we’ll then inject viscoelastic in the eye. And we use mostly a thicker viscoelastic than methylcellulose. We use Healon GV. And then we want to firm up the eye. Because when you’re pressing with the gonioprism, you’ll get artificial corneal folds. And you need a clear view. So you fill up the eye with a viscoelastic. And then you rotate the microscope. So you turn the microscope, and you rotate it so it’s approximately 30 degrees to the patient’s eye. And then you take the patient’s head and you rotate the patient’s head away. So all in all, you’re getting a view like this. And this is the eye down at the bottom of that. And that’ll give you the view of the angle. You cannot see the angle looking straight at it. Right? That’s why we have gonioprisms. So without this — and if you don’t do this right, the rest of it’s all gonna be a failure. If you can’t visualize the angle well, you’re gonna have a problem. So this is crucial. The crucial first step. You obviously can’t build the rest of the building if the scaffolding is wrong. So here we have an example of an iStent going in. You can see here’s the gonioprism. Here’s the iStent going into the trabecular meshwork. And then being injected and then released. Looks pretty easy, right? It took about ten seconds to do that. To cure glaucoma. It’s not that easy. It always looks easy when you watch someone else do it. When you do it yourself, it’s not that easy anymore. Well, let’s watch this again. So here’s the beginning. We’ve got a really clear view. No folds in the cornea. Coming in off a side port incision. Coming into the trabecular meshwork, into the canal, and then releasing. All right? To get from zero, the beginning, to that stage is gonna take a lot of practice and getting everything positioned well. But once you get there, once you begin to visualize that easily, it is straightforward. It’s a very straightforward surgery. It has none of the risks that we had with that Ahmed I just did, or a trabeculectomy. So let’s talk about some of the keys here. How many people do gonioscopy on their glaucoma patients? A couple. You have to get comfortable with angle anatomy. I know none of us… It’s a little more time in the exam. Patients don’t like it. It only takes a few minutes, but you can then get your anatomy down. You can understand what’s going on. And every patient that we saw in glaucoma clinic yesterday — I think we had 30 patients or so — every single one of them had pseudoexfoliation. Now, I know there’s other glaucoma but pseudoexfoliation here, but the vast majority have pseudoexfoliation, which really makes the angle even easier. Because they all have open angles, and they all have a lot of pigment. So that makes identifying that pigment area very clear. So you have to know the angle preoperatively. You’ve got to be able to did it. We gonio’d every patient yesterday, and for those that we were gonna do iStent on, we made sure that we had an open-angle. Now, you don’t have closed-angle very much here, so most of it’s open-angle, and most of it’s pseudoexfoliation. Head positioning. We talked about this. I can’t emphasize this enough, and when we get into surgery, I’m gonna really emphasize it again. Positioning the head away and the microscope towards you, to give you that view. If your microscope is coming like this, and the patient’s head like this, you’ll have a great view. If the patient’s head is like this, and your microscope is like that, you’ll have no view, and you won’t be able to see. High magnification. So once we get the view, then we really hone in on the mic. So we want to really mag up. Now, there are some different scopes — this scope is a really nice scope. You’ll be able to see it really well. Because we’re gonna really get high mag, and that’s what you need. You want to be able to identify the tissue as clearly as possible. So then how much viscoelastic? I said we want a lot of viscoelastic. But if you put too much in, you can actually distort the angle. You can push the angle back. You can even somewhat close off the canal. So just the right amount. Too little, you get folds in the cornea. Too much, and you can distort. So you’ll begin to know, and we’ll talk about that during my surgery later this afternoon. As you’re getting ready to inject it, as you saw in my earlier video, I’m gonna come in from the side, and then I’m gonna enter the tip of it, and I’m gonna pass it. But I’m not gonna pull back. The worst thing you can do is pull back. Because you pull back, and the whole iStent comes with it. So if anything, you want to continue forward. You want to inject and keep moving forward, and that’ll make sure it gets positioned well. If you inject and pull back, which — we all have a tendency to kind of shoot and retract — it’s gonna withdraw the iStent as well. So we’ll talk about that. So for iStent, we’re looking for the trabecular meshwork. One of the newer canal devices in the US is called the Hydrus. I’ll show you a picture of that later. And then here what we have is — this is for the CyPass. That’s where the CyPass went. Remember, the CyPass went suprachoroidal. So that was below the trabecular meshwork. A little bit different anatomy. Still want to press forward while injecting. And then when you’re done, and you think everything’s right, reassess. Make sure you’re happy with the position. And we’ll talk about: What is the target you’re aiming for? So the nice thing about these MIGs cases is they preserve the canal. It’s just affecting a small portion of the canal. You’re not irreversibly damaging it. The goal is to reestablish flow to the collector systems. And it’s nice, because you can actually see that flow. You’ll see that the collector system will begin to change color. It starts off red, of course. And as we begin to inject viscoelastic, it blanches. And it could be performed with or without cataract surgery. So when I started doing this a number of years ago, I actually began to look at my own numbers. I wanted to see what was gonna happen. And I started off measuring my first 50 patients to see how I was doing. You could see that the average pressure, pre-op, was 19, and it brought the pressures down to 14. And that holds. You get a good drop in pressure, and you have a nice reduction in medications that they’re taking. So in my case, what I do is: All glaucoma surgery, they’re usually coming in on medications. I do the surgery, and then I take them off all their medications, and I feel that’s a good chance to see what they really need. I don’t feel any reason to continue the eye drops, having had glaucoma surgery. Any questions so far? About anything? No? Okay. All right. So what is the target? What are we aiming for with the iStent? Well, of course, we’re aiming to get it in the canal. That’s obvious. The canal, of course, is where the fluid is going out, and the collector system. But there are some specific areas of the canal that are better than others. So you notice when you do gonioscopy that there’s areas of the trabecular meshwork that have a lot of pigment, and there’s some areas that have no pigment. Like here. You’ve got very little pigment in that part of the trabecular meshwork, and a lot of pigment over on the other side. Now, why is that? The reason is that there’s a lot of flow going into the collector system, where there’s pigment. It’s a little bit like a sewer or a drain. If there’s a lot of flow going in there, there’s a lot of leaves and everything else going in there. If there’s no flow, then nothing happens. And that’s what’s happening here. So you would not want to put the iStent on this side. You really want the iStent where the pigment is. Okay? So you’ll see later today, when we do this, we’re gonna look: Where is the pigment? If there’s blood or pigment, that’s our target. Question? So these are the current options. We have the original iStent, which is a single device. That’s what we’re gonna do today. They’ve come out with a new one. It was just released in the United States. Called the iStent Inject. That’s what this looks like here. And the iStent Inject comes in with almost like a gun, and you can place these two at a time. So you can put two stents in the canal. It’s a little different technique, in terms of placing it. But similar goals of finding areas of pigment. And the other new thing is this Hydrus. So the Hydrus is 8 millimeters long. So you’re scaffolding the canal, and you also have this snorkel that allows fluid to get in. So you have flow going in this system, and then it’s so extensive that it will find a collector system. Whereas here you’re hoping to find a collector system. There you’re guaranteed one, because it’s so big. I don’t know if that’ll be available here, but that just came out a couple of months ago. Any questions, anybody? In the beginning, the MIGs technology — okay. The MIGs technology was primarily geared toward early mild to moderate glaucoma. Not so much for advanced. And the reason was it didn’t get the pressure load off. You tend to get pressures down into the mid-teens. With trabeculectomy, if we’re successful, we can get it down to 12 or 10. Can’t do that with an iStent. I think with CyPass, we could have. But with the iStent, you can’t do it. So open angles, modest target, low risk. And then the MIGs 2, which is what we’re heading into now, sort of more advanced disease. Open or closed-angle. The CyPass, for example. That could be put into a closed-angle. You have to be able to identify where the suprachoroidal space is, but then once you get it, it’s very easy to do it. And the next generation has lower targets. So I know that this isn’t widely available here. I know it’s not gonna be easy. But I do think it’s important to understand it. I think it’s important to kind of get into this technology, because it’s coming. It’s gonna happen here. And it’s hopefully gonna happen in a more successful way than just a simple iStent. And so we selected a series of cases we’re gonna talk about — we’re gonna do iStent cases. We’re gonna do the Kahook blade. We’re gonna do all kinds of ways of looking at the angle, which I think will help you. So the MIGs 2 — we have — anybody heard of the Xen? Which is a subconjunctival MIGs? Have you heard of that? Yeah. So basically it’s a trabeculectomy done ab internally. Very simple. It still requires mitomycin. So you see that this is gonna pass… Here’s the target, where that blue light is. And it’s gonna inject a stent that’s gonna go subconjunctival with some residual into the anterior chamber. And from that, you create a bleb. So here’s the tip. It does not come through the conjunctiva. It goes through the Tenon’s. It stops with the conjunctiva, and the tube exits there and comes in here. So you don’t perforate conjunctiva, but you now have a hole through the sclera. And you have a bleb. The Xen data was actually interesting, in that it had very good pressure lowering. Down in the low teens. One of the problems with the Xen — it’s available — is that it requires mitomycin, and then requires a lot of needling and post-op care. A little bit like trabeculectomy, where you get some that are working, and then six months later, it scars down. Later this week, we’re gonna show you how to needle a bleb. But needling is a problem. It’s not easy. Patients don’t like it. So it would be ideal if we had a surgery where you do it once, it works, we can move on. We’re not quite there yet. We’re not there yet. Okay. So who’s a candidate? Well, I think anybody with mild to moderate disease that is — you could do phakic or pseudophakic eyes. It’s not hard to start implanting. We sort of talked about that. We’ll talk about that again. So here’s — it may be hard to see in the back, but a well-placed iStent in an area of pigmented trabecular meshwork. Here again — here’s three months postop. And the stent is like a hockey stick. So there’s an entry inside the eye and a snorkel in the anterior chamber. In this case, it’s going towards the area of pigment. That’s where the flow is. Okay? So the fluid would come in and flow out into the collector system. And that was really a very well placed iStent. Did yours look like that? Did the one you do look like that? No?

>> I would say no.

DR LEWIS: It’s hard at first. It’s tricky. It looks really easy. But it’s tricky.

>> Yeah. They are different.

DR LEWIS: Yeah. All right. Here’s another example. Good view. High mag. Area of blood in the canal. You kind of find the edge of the tissue. A little bit of bleeding, which is normal. You do often get bleeding in there. And then it’s in the canal. Okay? Yeah. Five minutes? All right. So one could question: Why did the company come out and recommend that it be done with cataract surgery? Because we know cataract surgery by itself lowers pressure about 35%. Cataract surgery is probably our safest, our best way of lowering pressure. Removing a cataract works really well. But there’s a lot of patients — in fact, about 20% of them — who have glaucoma, in which it’s not enough. You need more pressure reduction. So Glaucos went through the very rigorous process of getting this approved by showing that the combination of cataract and iStent lowers pressure more than cataract by itself. And then subsequently all of the rest of the MIGs companies did the same thing. So in general, the indication is to do this with cataract surgery, and that’s how we’re gonna do it this week. So when should an iStent be used? That being any patient with mild to moderate glaucoma undergoing cataract surgery, particularly in patients on one or more glaucoma medications. And it gives you a chance to get them off those other medications. I keep encouraging this point about gonioscopy. You’ve got to get comfortable knowing — for example, in pseudoexfoliation, there’s this dusting of pigment on the anterior to Schwalbe’s line, which is Sampaolesi’s line, which is not — that is not the trabecular meshwork. So you really have to be able to differentiate and understand the difference between trabecular meshwork and this Sampaolesi’s line, or trabecular meshwork and ciliary body band. What are the problems, if you’re injecting the iStent in the ciliary body band? One, you’ll get a lot of bleeding and pain. But two, it won’t work. There’s no canal there. So this fine pigmented band is our goal, is our target. But you’ve got to get comfortable seeing it. And there’s a website called gonioscopy.org. Incredible videos and images of the angle. And this is available to anybody, any time. It comes out of the University of Iowa. Lee… His last name… Lee Alward. Lee Alward did it. It’s a great site. I really would encourage you to look at this. Gonioscopy.org. Great way to kind of refresh yourself on the angle anatomy, as you begin to approach this MIGs surgery. Okay? And I keep saying: Practice before you do a scheduled case. Yeah. Yeah. It could well. You’ve got to get comfortable with the gonioprism. So, again, using a gonioprism in one hand and a Sinskey in the other, and then get comfortable intraocularly, is what I’m wanting them to do. All right. So let’s talk about some that aren’t so good. So what’s the problem here? Well, this one — you can see the iStent. It’s really kind of passed through the canal. It should be in the canal, and I think it’s too angled over, so you’re probably not gonna get much effect from that. It really should be in line and parallel with the canal itself. This one is in the wrong space. Less pigment, more pigment. You want to go in the area with more pigment. You want to target the collector system. And if you don’t have a lot of pigment, you often get blood refluxing back into the eye, and that’s another good target, is a little bit of — you can see the blood in the canal, okay? So, in summary, this is, I think, a wonderful opportunity, this week, to practice some of this. And then I don’t know when it’s gonna become available here, but I think it would be great to have it available. I think it’s a particularly useful tool. The iStent, the one we’re doing is the first MIGs procedure. There’s now four approved in the US. So we’ve got four different approaches to MIGs surgery. And the key is to get comfortable with the gonioprism. So questions for me? So the question — about using the iStent and medications — of course, will enhance pressure reduction even more. For sure. You can definitely do that. And I don’t know what percent of the MIGs patients end up on drops when they begin to lessen an effect. But yeah, it certainly works. And I think it does get your baseline pressures lower. So that’s a good idea.

October 10, 2018

Last Updated: October 31, 2022

Leave a Comment