Lecture: Glaucoma Drainage Devices

This lecture describes the types of glaucoma drainage devices and the indications for their use. Short videos of Ahmed Valve Implant and Baerveldt Glaucoma implant are also shown in this presentation.

Lecturer: Dr. Wallace Alward


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DR ALWARD: Hello. I’m Lee Alward. I’m gonna talk about glaucoma drainage devices, because we’ll be doing some today. So I can talk a little bit about when we would do a drainage device as opposed to maybe a trabeculectomy. So for me, where I practice, my first choice of surgery would be a trabeculectomy, because oftentimes I need very, very low pressures. And so the times that I would use a drainage device would be if I have too much scar tissue or they’ve already had failure of a trabeculectomy. And sometimes if people are working in a career where the environment is really dirty, so they can’t be around too much dirt, so maybe a seton would be better. A tube shunt would be better. Or if I think that they might not take their drops, because they need a lot of steroids after a trabeculectomy, or if I think they might not come back for follow-up, like they’re supposed to. So there are three different names for these. We call them glaucoma drainage devices or tube shunts or setons. It all means the same thing. And what they do is they take fluid from the front of the eye and put it back behind the eye to a plate that’s sutured to the eye. So the fluid goes through a tube to a plate that’s sewn on the eye. So this is somebody who didn’t do well after a tube. But you can see the tube is in the anterior chamber, where the arrow is. And then this is an eye that had a scleral buckle. That’s what that is. And this is a plate. This is the seton plate. And there’s fluid above it and below it. And it has a capsule around it. And the capsule limits the flow. So the pressure depends on how big the plate is, but especially on how thick that capsule is. And we really can’t control how thick that capsule is. So we’ll talk about two kinds of devices. One that has a valve. And that works right away. And one that we tie off, until the body forms that capsule. So like a trabeculectomy, it’s designed to increase outflow from the eye. It replaces the trabecular meshwork. So as I said before, unlike a trabeculectomy, you don’t need such nice tissue. So you can do this after other surgeries, after retinal surgery, after other kinds of trabeculectomies, other surgeries. It’s less dependent on having beautiful tissue. So there’s tubes — and the first case we’re doing today is a Baerveldt. The second case will be an Ahmed. So the Ahmeds have a valve in them that regulates the amount of flow. So these I use in somebody who needs the pressure down right away. So if the pressure is 45. And so these are two different models for adults, and then there’s a model for babies, which I’ve never used. So the one we’ll use today is called FP7. That’s just the name of it. So the other time I’d use this, besides eyes that have really high pressure, is if anyone has had steroids injected around their eyes. So if they’ve had Kenalog, long-acting steroids, they might not form a dome around a Baerveldt, and the pressure can go very, very low. And please have people raise their hand if they have any questions. I’m happy to stop any time. So the non-valved — what we’ll do today is a Baerveldt, which is my favorite. There’s a 250 and a 350. That’s how big they are. How many square millimeters. There’s also a Molteno. This is an old Molteno. There’s a newer version of the Molteno. But it too does not have a valve. So I like the Baerveldt, because for me, it gets the pressure lower than Ahmed. That’s why it’s my favorite. But it’s harder — a little bit harder to put in. And it has a little bit more problem with strabismus. So I use these when I need a low pressure. So in my practice, I have a lot of people who need very low pressures, so I like Baerveldts for that. If I need a lower pressure, that’s when I would do the Baerveldt. So usually when a trabeculectomy can’t be done, because they have scarred conjunctiva — we talked about this at the beginning — or if they have to wear contact lenses, contact lenses and trabeculectomy don’t go well together. If they have active inflammation or active neovascularization, I usually would not do a trabeculectomy. And, as I said, if they do a job where they’re working around very dirty things, probably not a good thing either, to do trabeculectomy. So I’ll go a little bit through the technique. Hopefully. It’s supposed to play on its own here. There we go. So I always do a paracentesis. And now I’m doing a peritomy. I’m opening up the conjunctiva. I open the conjunctiva pretty wide, because I like to loop muscles. And now I’m spreading in the quadrants. This is a Stevens scissor. You really need a lot of space. Make it very big, the space back there. And I like to loop muscles. Some people don’t do this. But I think for people beginning with tube shunts, it gives you much better exposure. Now I’m making a relaxing incision. Only through Tenon’s. Again, I want to be able to go very far back and have a good view. I’m measuring 10 millimeters back. Usually I try to get 10. At the very least, 8, but 10 gets me behind the muscles. And for the Ahmed, we need to prime the valve. So I need to push fluid through gently, until it starts to flow out through the valve. Right there. You can see it coming. Yeah. If you don’t do that, it won’t work. The air will lock it. It will never work. And now I slide it back in. It’s important that it’s very loose back in there. It should not be stuck on anything. And now I’m suturing it. This is a 7-0 silk. I mean 7-0 nylon. We’ll be using 7-0 silk here. It has to be a non-absorbable suture. We tie it very tight to the globe. So I sometimes will use needle holders to get it very tight. Checking it there. And now I’m going to trim my tube. I’m going to trim it with the bevel pointing up, so the iris doesn’t get captured. And now I’m trying to enter deep in the anterior chamber, so that I’m just above the iris, far from the cornea. So to me, this is just right. Where that is. It’s much easier to do this on eyes that are pseudophakic. So if you’re gonna start this, do it on pseudophakic eyes. And now I’m just gonna — with an Ahmed, I always fill the eye with viscoelastic at the end. Because sometimes the valve doesn’t work well enough. And now I’m covering this. In this case, I’m using cornea, which is what we’ll use here, that’s preserved in glycerin. But you can also use Tutoplast, which is pericardium, or sclera. And this is just a 9-0 vicryl. These patches don’t ever go anywhere. I’m trying to sew it down so that the front edge is as close to flat with the cornea as possible. So there’s not a lump. And now I just bring the conjunctiva forward, and I sew it at both ends, with a 9-0 vicryl suture. The same suture that I used for the patch. So any questions about that so far? I always do — the question is why do I do it early in the procedure. I always do a paracentesis before I enter the eye, so that if I have to reform the anterior chamber — you never want to try to do a paracentesis on a flat chamber. So any glaucoma surgery, I always do a paracentesis. It doesn’t matter. I can do it after I cut the conjunctiva. As long as I do it before I make my needle tract. Yeah. So he’s asking — is it 2 millimeters away from the limbus? No. I never measure the tube position, because every anterior chamber is so different. If you have somebody who is a high myope and pseudophakic, you can be very far back. And if you have somebody who has a narrow anterior chamber, you may need to be a lot closer to the cornea. The key is to be as deep in the anterior chamber as you can. And so to me, it’s something that I eyeball. And I’m often wrong. So I would start the entry, go a little bit forward, and then flat, to try to be parallel with the iris. If it turns out that it’s too deep or too shallow, then I’ll make another tract either right below it or right in front of it, and the volume of the tube will close off that original tract. So you can put two passes. It’s no problem. If you’re not happy with the first one. So if you’re gonna make a mistake, it’s much better to make a mistake too deep than too shallow. So one of the two ways you can really hurt an eye — one is by taking too deep a pass when you’re sewing on the plate, because the sclera is very thin right there. Especially in elderly people. Do that one first. So be very careful sewing onto the eye. It’s not trivial. And the other mistake people make is that they don’t go deep enough with the tube. If it touches any part of the cornea, over their lifetime, it will destroy the cornea. So sometimes it’ll be too deep, it’ll touch the iris, and the pupil will get distorted. That’s not a big deal. But if it’s too shallow, it has to be fixed. So with the Ahmed, I always fill the chamber with viscoelastic, as I said before, because sometimes the valve doesn’t work as well as I would like, but never use viscoelastic with a Baerveldt. Never, ever. So postoperatively, I have them on prednisone, four times a day, for a week, and then taper. And then antibiotic for a week. So the difference, then, with the non-valved, like the Baerveldt — I don’t irrigate the valve. I don’t fill the anterior chamber with viscoelastic. But I have to tie off the tube. So I tie it off with a 6-0 vicryl suture. And you have to be 100% sure that the tube is occluded. So always test it afterwards. So I’ll do a Baerveldt here. So almost everything is the same. The exposure is the same. And again, I think having done quite a few of these, I could do it without looping the muscles, but it’s better for you to start off looping the muscles. I think, anyway. I think Dr. Lee did it a different way. That’s fine. And again, you want to make this crazy big. The space. And just like before, I do this relaxing incision in the Tenon’s. This really, really helps me get great exposure. What’s that? Oh, thank you. Is that an insult? He said I would be a good retina surgeon. So, again, I mark 10 millimeters back. I think, as you get more experience, you want them farther back. Less trouble. And you can see it’s very big. So I slide it under one muscle. And I can even bend it, if I need to, to get it under the other muscle, and I want to make sure that it moves around freely. I’m grabbing the muscle here with the 0.5, so it gives me lots of control. So this is 7.0 nylon. The last case was 7.0 silk. As long as it’s not absorbable, and it’s a needle that you can safely pass through the sclera. So it should be a pretty flat needle. And now I’m tying this off with a 6-0 vicryl suture, and I’m gonna make sure that it doesn’t flow. I actually put some air in the tube, so I can watch the air compress and release. So nice and deep. Parallel to the iris. And then the rest of this is just like before. I throw this slide in, because this is how not to do a surgery. One of the people in our area has done this. But you can see that this plate is only 2 millimeters from the limbus. And the tube goes through the cornea. And we know that the plate didn’t shift to this position, because if it did, the tube would be all the way across the anterior chamber. So don’t do it like this, please. So what problems can people have afterwards? Sometimes the dome will become encapsulated. The dome is very thick. So the fluid is still flowing, but the pressure’s high. So this is the globe. Underneath it, it almost always gets flat, because the pressures are equalized. This is the plate. And then you can see fluid above and below the plate. So the newer Baerveldts, like the one we’ll use today, has these holes in the top of the plate. So fibrous tissue will grow down through them. So instead of having one big dome, it has a series of shallow domes. So they have less strabismus, less problems with volume. Strabismus, as I said, is a problem. If you compare it to trabeculectomy, these patients have more problems with strabismus. The tube can erode through. So the patch can melt away, and the tube can come through. And so this you can fix, if it’s not infected, by putting in another patch. These are — this is a plate that has moved. This is a plate that has moved. So this would need to be taken out. Another plate that has moved. And it can damage the cornea. So, again, don’t put it through the cornea. So I will stop there. The rest of this is on the TBT study, which Dr. Lee was part of. So he will know better. So all of my lectures are on this website. If you want to watch this again, if you’re really bored, you can go to that website.

May 16, 2017

Last Updated: October 31, 2022

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