Lecture: Point-2-Point with Dr. Malik Y. Kahook – Glaucoma Drainage Devices: Tips and Tricks from the Experts

Point-2-Point with Dr. Malik Kahook is a new webinar series that will take place once per quarter. During these sessions, Dr. Kahook will invite two colleagues and lead a fast-paced panel discussion. The sessions are specifically designed to address as many audience questions as possible in response to feedback from past webinars.

This session will cover both traditional and novel glaucoma drainage devices with a focus on practical information to improve intraoperative techniques and postoperative outcomes. Videos and a case-based teaching approach will be utilized along with ample time for questions and answers both during and at the end of the webinar.


Dr. Malik Kahook, University of Colorado, USA
Dr. Nathan Radcliffe, New York Eye Surgery Center, New York, USA
Dr. Maria Fernanda Delgado Morales, Bogotá, Colombia


DR KAHOOK: All right. Good morning, everybody. Thank you for joining us. I’m broadcasting in from Denver, Colorado. And we have an exciting session for you today. So I’m really excited by the amount of people that have signed in to join us. And also the specific discussion that we’re going to have, that is centered on glaucoma drainage devices. I’m gonna start off by doing an intro that is pretty basic, and then I’m gonna pass it on to our first speaker, Maria Delgado, and after that, we’ll go to Nate Radcliffe, to get us through some of the basics of glaucoma surgery, and then through some of the advanced techniques that Dr. Radcliffe will share with us. If we have some time between the sessions and between the videos, we’ll go through some questions, so please enter your questions on the Q and A you can see on the system, and at the end, we’ll try to leave some question and answer time. We’ll try to get through as much as possible in about an hour and a half or so. So I’m Malik Kahook, Professor of ophthalmology at the University of Colorado, I’m a glaucoma surgeon and cataract surgeon, and I’ve had a great time, really, participating in these point to points that I started with Cybersight. I think this is our third one, at this point. Just to give you a little bit of background, point to point is a series that we’re running, that is intended to be more discussional. So colleagues, friends, getting on Zoom, and having a discussion about all things glaucoma-related. It’s also intended to be more question and answer intensive. In my past talks with Cybersight, and with Orbis, we haven’t had as much time for questions and answers, so we’re gonna try to do that more and more, specifically with point to point. I’m putting my Twitter and Instagram handles here, so you can send me some thoughts that you have on what we can cover in future point to points. This session in particular came from an audience member suggestion. So please keep that up. And I’ll do my best to incorporate as many of these suggestions as possible. I also want to make sure that you’re aware of Cybersight. cybersight.org. The educational resources on Cybersight are tremendous. There are basic lecture series, one in particular by Lee Alward from Iowa is excellent. He goes over many of the steps for glaucoma diagnosis and follow-up. I put up an educational link, keogt.com, that has everything from basics of glaucoma through surgical videos that you can follow. You can also get consults on Cybersight, and there’s an AI capability, that allows you to upload your photos, optic nerve head and fundus photos, to get an idea of what you might be seeing if you’re a little bit confused about the optic nerve head and what the cup to disc ratio might be. So that’s a resource you can explore. I want to thank the Orbis team for helping to organize this, and congrats to Derek, the new CEO running Orbis. Exciting times for Orbis in general. I’ll do an intro for Dr. Maria Delgado. She’s working out of Bogota, Colombia, did her research in San Francisco, her research is focused on early detection of glaucoma in patients of all ages, and she’s an expert in everything glaucoma, from filtration surgery to advanced laser techniques. You can see a lot of her videos and I know many of the audience members are already aware and know Maria very well. So I’m excited to have her join us. Nate Radcliffe, who seemingly has done his fellowship on Zoom, because he’s been in almost every Zoom talk that I’ve seen since the pandemic started. He’s an associate clinical professor at Mount Sinai, has had great training at NYU at New York Eye and Ear, his research is focused on surgical glaucoma, and a lot of the diagnostic research that we’ve seen recently, that is a little bit different from the mainstream OCT visual field has come from his team, including corneal hysteresis. But the focus today is going to be on the surgical management of glaucoma with glaucoma drainage devices. We’re gonna go over the basics of glaucoma drainage device surgery with Maria taking the lead on that, Nate is gonna go over some of the techniques he does in the operating room. If we have time, we might go over some complications that can happen. We might not get to that. And I’ll show you some links to videos if we don’t get time for that. And keep the audience Q and A coming in as we’re going through. There are different glaucoma drainage devices that are out there. This is certainly not a commercial discussion, so we’re gonna focus basically on glaucoma drainage devices in general. A lot of the videos that you’ll see will be the valved version, the Ahmed valve, which is more commonly used, outside of the US in general. If you look at the numbers, it’s about 50/50 in the US, valved and non-valved. Outside of the US, it’s mostly valved devices that are being used. So we’ll cover both of these in our discussions and our question and answer. I’ll get to some videos if I can. But hopefully a lot of the time will be taken up by Maria and Nate. And before I hand it over to Maria, I want to reiterate: We’d love to hear your thoughts on this session. Send notes to Cybersight, to Orbis, and you can get in touch with me on both Twitter and Instagram, and let me know what you think and what we can do better. So I’m gonna stop sharing here, Maria, and ask you if you can share your screen and get started. Nate, you can stay on mute, but I’ll ask questions back and forth. So if you have any thoughts as we go through, please chime in, and we’ll go through from there.

DR RADCLIFFE: Looking forward to it.

DR KAHOOK: It’s all yours, Maria.

DR DELGADO: Thank you! It’s a pleasure for me to be here, to share, and to learn. So I’m gonna start to mention that: Like you say, drainage devices are pretty common. Especially valved. At least in Latin America. We have more experience with the valved than the non-valved, because of the availability. And they have been used mainly in refractory glaucomas, but of course in different cases, we can also use it as a first choice. Like, for example, neovascular inflammatory cases. In many of the videos we might see today. So I just wanted to start by saying that always keep in mind that you’re choosing a surgery for a patient, so try to choose the right surgery for that right patient. Not everything is for everybody, and you have to consider the baseline disease, the eyelids, of course the lens status, if it is phakic or pseudophakic or aphakic, the chamber and the angle depth, if you have vessels, if you have a clear or a cloudy cornea, endothelium, of course, you have to take into account the scarring of the conjunctiva. If you have a patient with previous surgeries. What is the medical therapy, if the patient is on maximal medical therapy, and the IOP goals you want for your patient. So to start, we’ll go from basic to complex. I want to mention the anesthesia, which is of course very important. At the beginning of our training, probably, we start using more of a block, to have the patient to cooperate better. But now I’m preferring the local just infiltration in the subconjunctival space. I feel that the patient is very comfortable with with this type of anesthesia. And actually, the surgery flows perfectly. And it’s very simple and quick. Like you may see in this video. You just form that bleb, and then you’re ready to start. Then one of the most important things is that you have to have a traction suture. Because you want to work in a space which probably in most of the cases is the supratemporal space, and the traction suture is going to help you to have all the exposure, and some people do it in the rectus muscle, for example. But I prefer the cornea, because of course, there’s less bleeding. But you have to be very careful and be very careful because… If you go deep, you may perforate, and there you’re gonna have to lead with a soft eye, which is very uncomfortable for the placing of the plate. And you have to do it like in a long — do a long run of the needle. To have — to prevent it from of course falling off. Probably when you’re tractioning the eye, downward. Then the conjunctival incision. Which is of course very important. You have to manage the conjunctiva very softly.

DR KAHOOK: Maria, before you get to that point, maybe if you could pause the video. We’re gonna do this a lot to you. Nate has a tendency to interrupt like crazy, so just be ready for that. The previous video — it makes me think of — when you’re training a resident or a fellow, and they pierce, they go through the entire cornea, there’s sort of this freakout moment where it’s like — oh my God, I just went into the anterior chamber. What do I do? My thing for that is: Just keep going. Get the bridle suture in and just create a paracentesis. Put some viscoelastic in. The patients tend to do very well. You don’t have to think about suturing or doing anything. Nate, do you have that experience as well? Do you put the bridle suture in the cornea, or do you go old school and use the muscle?

DR RADCLIFFE: You know, somehow I’m able to keep eyes in primary position. But this technique is essential for any glaucoma surgeon, to be able to control the eye position. And I agree — you know, one of the great things, particularly about using an Ahmed valve, is you can always fill the eye with viscoelastic, and leave it there. Never to be removed. And it takes away all the concern about leaking paracentesis, leaking wounds, leaking traction suture tracts. Because there’s just no tension on the cornea at the end of the case. The chamber is gonna stay deep. And over three days, while the eye is sort of filtering through that viscoelastic, you’ll have usually a good chamber, and not have to worry about leaks. So it’s a gift. Same with — if you ever have to suture an IOL with an Ahmed, you just leave the viscoelastic in, and that IOL is gonna be much more stable than if you had to clean it all out.

DR KAHOOK: I know Maria is gonna get to the paracentesis and viscoelastic a little bit later in her talk. This is great feedback. Sorry for interrupting, but we’ll do it again.

DR DELGADO: Perfect. Let’s do it again. Let’s do it. So the conjunctival incision — this one that you’ll see in the video, I’m going very limbal. I know some people want to go some millimeters behind the limbus. And it depends of course on the experience of the surgeon, and his or her preference, but I like it like this. Because you have a good coverage of the valve and of the tube after you finish. And also, you have to take into account if the patient has some adherences or previous surgery, that of course will make it difficult, and you have to be very gentle with the conjunctiva. You don’t want to be rough and then to have maybe a perforation, or to have — not the amount of conjunctiva that you would need for covering. So in this case, you see that we start with the Westcott scissors, just for the first part. Preserving this conj. And then we move to go to do the sub-Tenon’s pocket, actually. And this is very important, because that’s of course where all your plate is going to be placed. So you need to have a good space. I do this like probably all of us with the Stevens scissors. You have the Stevens scissors that are straight and some that are curved. I of course prefer the curved. I think that it goes smoothly. And you go and dissect very easily the pocket, to hold the plate sufficiently. Then the valve priming is absolutely mandatory. It seems obvious, but if you forget, then the next day you’re gonna be with the patient with a high pressure, and then you’re gonna do something to have to open the valve system. And priming is very important also not to do it. I don’t know what you think… Probably we can open of course discussion in this. Not to do it so forcefully. Because if you go so forcefully, you probably will damage the valve system. What do you think about that?

DR KAHOOK: So the previous video that you showed, I think, is a really important one. I remember in fellowship, when I was learning different techniques on doing tubes, whether it was valved or non-valved, this step of taking a curved Stevens scissors and going back and dissecting and really spreading — my mentors, the people who trained me, always used to say this is the most important step in glaucoma drainage device implantation, because it can be really frustrating if you don’t go back and spread the scissors as much as you can, and that’s what you’re doing in the video. You’re not being shy about opening the scissors underneath Tenon’s capsule. Getting enough room to put that plate in — oftentimes, when you see trainees doing this for the first time, the plate goes in and it keeps spitting out, and they can’t figure out why and can’t put it back in, and if they don’t have an assist when they’re doing this on their own, it can be really frustrating. I know we have a lot of residents and medical students who are listening in. This step of using curved Stevens scissors, keep that in mind. It’s extremely important. There are other parts of the surgery that get more attention, but this is extremely important. I’ll ask Nate for his opinions on this — I think the priming part is a question that we get frequently. I do some work with New World, and every now and then — this is the New World Medical Device, the Ahmed valve. Calls will come in, saying: Hey, is it supposed to be a stream that’s coming out? Is it supposed to be a trickle? There is no one to one relationship between the valve function and the stream that you’re seeing coming out. It doesn’t have to be a big stream. You don’t have to be forceful. It can be a really soft kind of trickle that’s coming out. Similar to what you just showed in the video. Nate, what’s your experience with it? I think you’re the number one Ahmed user in the world these days. So you do a ton of these. What is your take on the priming part?

DR RADCLIFFE: Yeah, you know, actually, one interesting thing is I’ll have my technicians prime in some cases. They seem to get it done. You know? So if you ever take the Ahmed valve apart, it’s probably not quite what you think. It’s basically two pieces of almost a material like… Not quite Saran wrap, but a flexible little film. And they’re just forming… You know, a little bit of pressure, tension, so that the fluid kind of only really pushes one way. So it’s not something that can be blown apart. Or — it’s really a flap, a plastic flap, made out of a flexible material. So I don’t as much worry about too much pressure harming it, which I have heard is a concern, but I’ve never seen one where I felt like an overprime did damage.

DR KAHOOK: That’s right.

DR RADCLIFFE: And of course, vasc is gonna be coming through that thing after in most cases. And that doesn’t seem to damage it or do anything either way. So I feel like it’s a robust mechanism. And as long as you get some aqueous going through, you’re good to go.

DR KAHOOK: This is great. Maria, you’re showing a lot of really good pearls here for people. So keep it going.

DR DELGADO: So now the suturing of the plate. I’m showing this before introducing the plate, just because I’m right now doing it outside of the eye. I don’t use the two holes to put separate stitches, but I just make one long throw. This is a 7-0 silk. Like you see. I just prep it before putting it — the implant — in. And then if you made the good pocket, like we were saying, then it will slide very easily in the place that you want it to be.

DR KAHOOK: That’s perfect, by the way. Looking at what you just did, I think, is kind of the example that we were talking about. There was no — I mean, this is an expert surgeon doing it, of course, but there’s no kind of spitting out of the plate. So perfect example of it.

DR DELGADO: Right. Then you have to fix the plate to the sclera. Which is very important. Remember that you’re around 8 to 9 millimeters behind the limbus. So there the sclera is of course thinner, and you don’t want to go too deep. Of course here, we were saying in the cornea it’s okay. Here it’s not okay. You don’t want to perforate the sclera and go inside the eye. So you have to see the needle. Actually I want to see the needle, translucent, through the scleral tissue that I am working in. Here’s a little bit of entanglement of the suture. Then we have it fine, and then of course you’ll have your compass to measure that you’re in the correct position, for tying, before tying. You want to see that you’re in the right place, in the actual… The good length that you want to be.

DR RADCLIFFE: I really like that. That’s a really great idea, actually. I hadn’t seen that before. Usually the surgeon is trying to suture through the plate. To the sclera. You add a lot of variables. It’s tough to keep the eye in that position. And here you’re making good control over the surgical field. For ideal placement, and then you just simply slip the tube on later. It’s great.

DR DELGADO: Mm-hm. Good. So then the tying… What I wanted to say about tying is that if you have — if you see your plate, and you tie, and you firmly tie it, you are avoiding sagging. Sometimes you tie, you make your knots, and then the plate is not really in the good position. Then it’s loose. So then you have to — a plate that may move forward, or then you may have to cut again and just tie it again. So you have to avoid sagging and tie firmly. This is a very thin sclera, multiple retina surgeries, so be careful. But then you look and you see actually that your knot is behind the end of the plate, and then you’re safe to continue doing some knots and tie it firmly, and then cut. And of course, the tube will be — the knot, sorry — will be hidden behind the plate.

DR KAHOOK: Maria, can you comment a little bit about the suture that you’re using? Different sutures?

DR DELGADO: Right. This is a 7-0 silk. I remember at the beginning, when I was in training, many of my attendings used nylon. But I actually moved to the silk. I think it goes firmly, and I don’t have any special reactions with it. And I think it’s a good suture to have for many years.

DR KAHOOK: Okay. I know Nate doesn’t really use suture. We’ll get to that a little bit later. But for me, I use 7-0 vicryl. And I do that, because it’s the same suture that I use for the corneal bridle suture. It’s more efficient for us to just keep using — in some cases, we can get away with just using one double armed 7-0, for the majority of the case, and then we can use that for closing conj as well, which we’ll get to. But I think that’s one point, for people who are starting to learn, and doing this technique. Get a little bit comfortable. The vicryl is gonna stick around long enough for the capsule to form and hold the plate in place, so we’re okay with that. But a lot of this depends on who trained you. Also, if you can comment a little bit on the slippage that you were talking about, so are you talking about the plate moving forward towards the limbus after implantation?

DR DELGADO: Towards the limbus, right. If you don’t tie it firmly, and probably the suture is loose, then you’ll have a plate that is probably behind, and you’re not aware of it. And then when you close and you finish the surgery, probably you are gonna see that your tube is longer than you really expected it. And it’s probably because just the valve moved a little bit, because it was not firmly tied or firmly placed in the spot that you wanted.

DR KAHOOK: Yeah. One thing that we talk about a lot is sort of how to put that suture into the sclera, in relationship to the limbus, so if you’re putting it perpendicular to the limbus, and you’re a little bit more anterior with the placement, then that slippage is gonna be more frequent. If you can go tangential or partially tangential, to the limbus, then it’s gonna be more of a side to side movement, rather than a front to back, so I think keeping that in mind, when people are doing this procedure — and you don’t want this — how far back do you go for your plate implant? Where do you put it in relationship to the limbus? How far back do you go, typically?

DR DELGADO: 9 millimeters, supratemporal. If I go nasally, probably 8.

DR KAHOOK: Nate, what do you do from a placement standpoint? You just try to go as far back as possible, I think, right?

DR RADCLIFFE: Yeah, for me, the key is to get the plate behind the orbital rim. And once it’s behind — it’s interesting. Here you have an eye that’s been pulled down with a traction suture. The forces acting on the plate will change a little bit, once the eye is back in primary position, because the orbital rims change. That can be good and help keep the tube back, or put force to push it forward more. It depends on how shallow the patient’s orbit is. I keep that in mind. But for me, it’s probably 10 millimeters. The downside of my technique is sometimes I can’t find a plate, postoperatively, because it’s really a retrobulbar Ahmed valve. If you can conceive of such a thing. It’s not so much a tube anchored to the sclera.

DR KAHOOK: I think this is a really important point. Because you’ll hear a lot of fear as to how far back you can go in the limbus. From the limbus. And if you’re supratemporal, the package insert says 8 to 10 millimeters. The reason for that is if you go further than 10 millimeters, in some cases, the plate can actually touch the optic nerve. And there’s been some research on that, from Ramesh Shyla and others, showing that that can actually impinge on the nerve and cause some damage in itself. But it also depends, as Maria said, on what quadrant you’re going into. So if you’re going inferonasal, you don’t have as much room. If you’re gonna infratemporal, you might actually have a different set of parameters, depending on the axial length of the eye. So that’s one thing that’s worth looking at, after this discussion. For anybody who is interested. Just look up the literature from Ramesh Ayala. We have a publication on that, and Friedman from Duke actually has an algorithm that you can go in and type in the axial length and the plate, and she’ll actually show you exactly how far from the limbus you can get, and she does a lot of pediatric surgery, so that was the reason for it, with the shorter eyes. Really important point that doesn’t get as much air time, but where you put it from the limbus is extremely important. All right. Thanks, Maria.

DR DELGADO: No, thank you. And after you tie… You’ll have to make the cut. Of the tube. In a bevel fashion. Depending if you’re going in the anterior chamber — you probably will go bevel up, and bevel down when you’re going in the sulcus. And measure accordingly to what length you want inside the anterior chamber. Or if you even — maybe sometimes you can cut it a little longer, and maybe if you want you can leave some tube in the sclera, if you probably think you may need some tube for the future, in certain cases. So this is — sorry. I didn’t play the video. So this is the way, with the Vannas scissors, and just to have the bevel is nice, because also, it helps you to get into the tunnel, when you are just introducing the tube into the AC. And here… You were mentioning the paracentesis, and the viscoelastic — I put there in the parentheses not always. Because I probably — not always — use it. In many cases, yes, I do. The paracentesis will help you to have access in case you need it, and also to provide tone to the eye, if you need it, and of course, the viscoelastic like Dr. Radcliffe was mentioning, is very important, and you can leave it, and not be afraid of leaving the eye at the end of the surgery with tone and of course not in hypotony, which would be not ideal. So this is just something maybe if you want to talk about it, just in some cases, what cases do you use it, or do you use it always.

DR KAHOOK: What do you do, Nate? What viscoelastic do you put in?

DR RADCLIFFE: I use Provisc. I think Healon is acceptable. And if I’m not mistaken, I even know some surgeons who use Viscoat. So I think you have some choices here. I would personally stay away from something like Healon 5 or even Healon GV, unless I knew I was headed for hypotony, like the other eye had a bad problem. So I use Provisc. I leave as much as I like in the eye. So you do not need to hedge. You can absolutely pack that eye, filled with Provisc. And unless the iris gets clogged, you’ll be fine. You know, the iris clogs the tube. The one thing that is true is that: Iris clogging a tube, if the eye has Provisc in, will result in a very high pressure. So when you leave a lot of viscoelastic, those careful post-op day one exams are critical.

DR KAHOOK: Yeah. So I’m very similar in practice. I don’t leave quite as much in. I was a little bit surprised when I was first starting out with tube surgery, on the variability. Some people are like Nate. Just fill the whole anterior chamber. Others might be a little bit more worried about it. If you’re using Provisc, Viscoat, or even regular Healon, that is a little bit more cohesive, you’re gonna be fine. And we’re talking about the valved devices, by the way.


DR KAHOOK: With the technique that we’re mentioning. GV will result in significant spikes in many patients. So I would avoid using anything GV or above, like Healon 5. So yeah, practice patterns are a little bit different. And Maria, just so you know, from a connection standpoint, your videos are a little bit slow. They’re not fully playing inline. But if that’s an issue coming up, we’ll have Lawrence step in with a deck that he has. But so far, so good. This one we can see.

DR DELGADO: So we continue with the scleral tunnel, which is also a very key point in the surgery. There you go. Do you see that it’s not at the limbus? It’s behind the limbus. Probably if you want to go 3 to 4 millimeters behind the limbus is okay. It depends of course also if you are using or not using the scleral patch, and we will see that in a few minutes. But then you see the needle. You then change the trajectory of the needle, so when you’re perforating, here we’re doing a very short tie. And as you see, I’m opening with the needle. I’m going behind. I’m going through the sulcus. But opening… Closed iridectomy from the previous surgery — because I want that iridectomy open. Not only for opening it, but also to see my tube, which I wanted to go through the tunnel, and insinuate — I’m gonna show you here, before you go with your video — because I want to try to put the tube in. And try to make it, let’s say, come out through that opening, just to see it. And then you see how it magically, perfectly goes like that. So I’m gonna stop sharing, so that you can show your video. Right?

DR KAHOOK: Thanks. Yeah. I’ll show mine here as well.

DR RADCLIFFE: I liked what you were doing there. Going back and forth. Because the reality of entering the eye with a needle is that it’s not a guarantee that the tube is gonna follow the same pathway. And I can tell you how many times my needle has gone in the anterior chamber, and then my tube comes through the sulcus or vice versa. And keep in mind, we operate on a lot of eyes with PAS. And there is no ideal place to enter the angle, because there’s no angle. It’s all iris. And so in some cases, in order to protect the cornea, you’re gonna have to come in right where the iris is adherent, and you’re gonna have to go back and forth, and create the pathway. And that’s where injecting viscoelastic as you come in can push the iris back, and then sawing back and forth — basically saying: Hey, in a minute, when the tube comes through here, I’m making a pathway — can be just so helpful, and you want to do that, rather than put a tube too close to the cornea. Because that’s the critical thing. And so I liked what you did there.

DR KAHOOK: You’ve mentioned a couple things, Nate, that are, I think, important. When we do this, we use a 23-gauge needle, and we put it on viscoelastic. So when we’re going in, we’re prepared to deepen the chamber. And use it as a manipulation device. The OVD can move things around, if need be. Because some of these eyes don’t have an angle, and you can manipulate it with the needle and the viscoelastic. There is a debate as to whether to use a 23 or 22 gauge. Surgeons use both. There’s a question as to whether you’ll get more peritubular leakage with a 22-gauge. But surgeons get away with it just fine. And they’re very good surgeons. So you can probably use both. How far you go away from the limbus for your entry is extremely important. If you’re closer than 2 millimeters, that’s gonna be a point where you’re gonna get erosions. We’ve had a couple of questions about how we handle conjunctival erosions that we’ll try to get to towards the end here. One of the things that I learned in traveling was the Z technique for entry that Felix Gil taught most people in Central and South America. And most of us learned here from Felix. To go way back and not use any type of tutoplast or patch graft. But one of the things people have a problem with when they’re first starting is getting the tube into the scleral tunnel. There’s a lot of fiddling around that happens. So the way we do it — I’ll just play this video here, so you can see. When we’re coming out, we actually sideswipe. Do you see that here? I’m gonna play this over again. And I’ll try and pause it. As the needle is coming out — the needle tip, so now you’re completely inside of the tunnel, no longer in the anterior chamber — the tip of the needle swipes this way. That gives you a little bit of a lip to get the tip of the beveled tube into the tunnel, so that it goes in a little bit more easily. So I’ll play that here so you can catch it. And then at this point, the tip is gonna start swiping here to the side, just teasing a little bit of the sclera to create a little bit of a flap. See that there? So for trainees that are first starting, the tube goes in every time when you do it that way. It’s just a point that is very frustrating for trainees, and that’s one way to fix it. Won’t be an issue if you can do it that way. I’m gonna stop sharing. Maria, I’m gonna send it back to you.

DR DELGADO: Okay. So the other thing to mention is to always touch the tube with non-toothed forceps. Try to be gentle with the tube. You don’t want to rupture it. Which is also important, to avoid damage. Then one other thing that maybe is not routine, or very common, is to suture the tube to the sclera. Many times, I really want the tube fixed to the sclera. And I do this with nylon suture, and then you bury the knot in the sclera. And especially if I want to do something like you see in here, which is to make a little curve in the tube, and it is not occluding the tube — it’s just making a curve, actually. Just kinking it a little bit, without occluding the lumen — and what do you think about this? Do you do this in some cases, or do you fix the tube to the sclera?

DR RADCLIFFE: Yeah, I’ll make a few comments. First of all, it’s a very wise thing to make that type of tract that you have there. For so many reasons. Number one, if this patient ever needs a reoperation, you’ve got extra tube length to play around with. If they have an erosion, you have — and erosions happen. Some number, 2% of tubes, something real — and you’ll be able to reposition, come in through another quadrant, and that extra length is good. You’ll have a tube that’s much more stable. And the way you kind of gave it a sinusoidal pathway makes the tube itself less likely to migrate in the anterior chamber. A tube that’s most likely to migrate is one that comes straight in, because it’s very easy to go in that direction. Once you add a curve, it won’t move as quickly. And so all those things are good. They take a little extra time. But they can just sort of overall benefit the tube placement. The other thing that you’re really making sure here is: The worst thing to do is to go through all the trouble of putting a tube in, and find out that you don’t have enough tube to get into the anterior chamber adequately, and adding this redundant part of the tube makes sure that can never happen.

DR KAHOOK: Yeah. And Maria, your videos are choppy here. So what I’m gonna ask you to do is to unshare. I’m gonna ask you to share my screen. I have all your videos. So we’ll play them for you and see that that makes a difference. I’m gonna go ahead and share. And then I’ll go to the video that you just had on. Which I believe is this one? And I’ll go to the next one here. And play the video for you. So scleral patch.

DR DELGADO: So the scleral patch — we use the scleral patch. We don’t have tutoplast or any other material when we need it, but the eye banks have availability quite easily, I may say. So if we need it, we use it, and it’s no problem. And I really like to cover the tube, in many cases. Especially cases where the patient has multiple surgeries, cases where probably the sclera was too thin. Probably myopic eyes, which, by the way, have very thin scleras. And to cover it, I just throw two nylon sutures, hiding the knots, below the patch, and I don’t have any issues, thinking that it may make the scarring process worse. Which some people say that they don’t use it, not only because of the extra time, or the little availability, but also because of the scarring process.

DR KAHOOK: What do you do, Nate, for your patch?

DR RADCLIFFE: Okay. This is where I definitely love glue. You know, hands down. The first thing — and you’ll hear — but I went through an evolution in my technique. Where I used to sew the patch graft with two nylons, or maybe even four, once upon a time. And it is interesting that the patch graft doesn’t have much reason to move, once it’s tucked under the conj there. So I’ll typically not suture that. You can suture your conj down, leave the patch graft kind of free, and it’ll usually stay right there. But I agree. I still use patch graft. And there are lots of surgeons who kind of have gotten off it. To me, it just provides an extra barrier of safety. I will use pericardium on initial surgery and sclera, if they erode. And that seems to work pretty well. I do agree the scleral patch graft is just bullet proof, in terms of… It would be interesting for us to compare erosion rates. Because it may be that I see more, because I use pericardium. You know, I could calculate it. But I may have… If I do 300 tubes in a year, I’ll maybe do 10 erosion repairs. So maybe a 3% erosion rate. Something like that.

DR KAHOOK: So I do something similar to Nate. So I glue pericardium, and that’s a step that, for us, saves a significant amount of time. And we close the conj with glue as well. We’ll hold off on that, because Nate is gonna show a video of that in a little bit. So should I go ahead and play this video?

DR DELGADO: Yeah, for the conjunctival suture, I’ll do the same suture, the bridle suture, you do in the cornea. Routinely probably a 7-0 or an 8-0. This case, for example, does not have a patch, actually. So just make sure that you tie the edges. You don’t have to make — I don’t make a continuous suture. I probably think that it — well, when you cover the limbus, and you handle the edges, it goes pretty well. In most cases, you don’t have any issue with that. Do you close with the vicryl as well?

DR KAHOOK: So I close with vicryl, and I close it with either 7-0 or 8-0, 7-0 typically, because we’re using it for the bridle suture, as you said. We do only two interrupted sutures, and we use glue for most of the closure. In some cases, with very mobile conj, we’ll just do the Tisseel glue. I remember the first case we did with Tisseel glue was 2005. We did a publication in the British Journal of Ophthalmology on the use of glue, and we got a lot of hate mail after that. There was a lot of pushback in the paper at the time. I was working with Rob Noecker, and we were both sort of maligned for a couple of years, in saying that this was possible. But now that’s routine for Nate. And Nate took it ten steps further.

DR RADCLIFFE: No one’s ever given me a hard time about it, Malik.

DR KAHOOK: That’s right. You’re just kind of sailing through life. But I think when we get to Nate’s video, this is gonna be an important point. Suture works very, very well, but Tisseel glue is not accessible everywhere. Maria, what were you saying? Sorry to cut you off.

DR DELGADO: I was saying it’s not very accessible, primarily because of the cost. If you’re gonna just do one case, it’s very over the top for the OR. But I would love to do it.

DR KAHOOK: Yeah. So $200 per vial — you can use it for multiple cases, if possible. And you save a significant amount of time by using it. So you save on OR costs. But you’re right. I mean, it’s definitely a barrier.

DR DELGADO: Okay. So then we go to the… We’re finishing. So you go to the… To reforming the AC. To make sure that you have your — if you made the paracentesis, make sure if you have viscoelastic in the eye, it’s gonna be okay, check the tone of the eye, you can go to the next one, because checking the tone is gonna make sure you’re not gonna leave the eye in hypotony. It’s better to leave with higher pressure in the post-op than leave with very soft eye in the post-op. Because of the risks of complication. Check the tone of the eye. I don’t know why we do that. We check the tone of the eye with the cannula. But it’s pretty easy to see how the cornea… What the tone in the cornea is.

DR KAHOOK: Yeah. Common question… And I’m gonna say something that’s not very scientific at this point. But it’s a common question that… When you’re with trainees and you feel the eye with your finger and you say — that’s about a 20. They’re like: How do you do that? The truth is, we don’t do that. It’s not really that accurate. But if you are pushing on the side at the limbus, with the BSS cannula, so the bottle cannula, and the iris is moving significantly, if there’s a lot of excursion of the iris when you’re pushing on the limbus, the pressure is probably 15 or less. If you’re pushing on the limbus and the iris isn’t really moving at all with that pressure, you’re probably around 15 to 25 or so. That’s what I found out when I started. So it’s really just making sure that you’re not in the 50s or 60s. When you have the viscoelastic, it’s kind of a moot point, really. You have a valved implant in there. You’re not as worried about the early postoperative fluctuations that might happen. And that’s one big benefit of using the valved device over the non-valved device. You just have a lot more wiggle room. Nate, do you do things differently? I’m sure you do.

DR RADCLIFFE: No, I agree with you. There are some odd things that are happening with Ahmed valves, filled with viscoelastic. Like, for example, oral Diamox actually can keep the chamber formed a little longer. Because it reduces the aqueous rate and keeps the viscoelastic in the anterior chamber for maybe another day or two. Because it’s the aqueous that’s eventually gonna push the viscoelastic out of the anterior chamber. But I do play a game with the residents where I tell them: Try to guess within 10 millimeters of mercury what the pressure is gonna be tomorrow. You would be surprised how often we’re wrong. And it’s just a high amount of variability. And that includes valved and non-valved tube shunts. It’s just variability abounding.

DR KAHOOK: That’s part of glaucoma surgery. Sorry. Go ahead, Maria.

DR DELGADO: Yeah. I was gonna say: You feel quite safe when you’re using the Ahmed. But I’ve seen hypotony. I’ve seen cases where things don’t go as you expected. And then you have to manage how to get out of that.

DR KAHOOK: Absolutely. So Nate, I unshared here. If you can go ahead and share your part — thank you, Maria. Now you get to grill Nate on a few things. Feel free to make fun of Nate’s technique, because no one has apparently given him a hard time on how he’s done things. So that’s what we’re here for today. So Nate, let me know if you have a problem sharing.

DR RADCLIFFE: No problem. So I had a surgery a few years back, where the patient was just not tolerating anything, and the anesthesiologist looked over and said: This surgery has to be over now. And I had put the tube in. I had put the tip of the tube in the anterior chamber. But there was basically nothing else. I hadn’t put the patch graft down, I hadn’t sewn anything. And I took one stitch of vicryl and kind of reapproximated the conj, and that was the end of the surgery. It was an emergency. And the patient did shockingly well. I think my first observation was that I used less steroid, postoperatively. Because I think part of my prednisolone use over the years was just fighting my own vicryl. Which does have inflammation. So eventually I went back and revisited, step by step, over probably 5 or 6 years and maybe a thousand cases, to try to cut out as many steps in the Ahmed valve as possible. While maintaining a safe surgery that’s efficient in the OR. And heals well. We’ve published our results. But here’s the technique that we’ve arrived at. So I begin with a conjunctival peritomy, about 6 millimeters behind the limbus. I’m starting the video. There’s an area where the conj and limbus thicken and start to get into orbital tissue. You dissect down to the sclera. You see that little barrier there, and I get into this superotemporal space. This can work in any quadrant. And again, Malik, you described the importance of getting in the right plane, of spreading with those scissors, and collecting the Tenon’s as you go. And you don’t want to overdissect that pocket, because that pocket is gonna hold your Ahmed valve in place. So you want it to be a bit of a tight fit. Here I’m making a dissection where my patch graft will go. And you see there’s not gonna be any tension on this wound, because it’s relaxed and it’s back. So when we go to close it with glue, we’re not counting on the glue to kind of hold things together. We’re just counting on the glue to keep a reapproximation.

DR KAHOOK: I have a question for you, Nate. You said you want to have the pocket hold the Ahmed plate. Are you controlling that by how far you’re separating the scissors?

DR RADCLIFFE: Yeah, and you’ll notice it’s a tight squeeze even with me getting this tube in through my conj dissection. So I don’t want — this concept of overdissection, which was never a concept when you’re sewing, you want overdissection if you’re sewing — but the concept of this surgery is we’re using the tissue to maintain some stability and some structure, and making smaller pockets that almost squeeze your implant are sort of gonna help you here. And ideally, there’s sort of a bottleneck, right after this goes in, that won’t let the tube slip forward, because I hadn’t dissected enough conj to allow that to happen.

DR KAHOOK: Got it. That’s a subtlety I never got with your procedure. I’m glad you said it.

DR RADCLIFFE: Yeah, I’m fighting it a little bit. I have to wiggle. The answer here how far back I go is… I call it deep-sixing the tube. But it’s gone. And now I’m going to tug to make sure it can’t come forward. So that’s the orbital rim, locking that tube into place. Now I’m gonna cut. And I’m gonna plan for a little turn. That turn that I just showed you there is what’s gonna help prevent the tube from sliding in and out. Because that little turn is actually enough to cut some of those forces down, and so you’ll see here —

DR KAHOOK: Maria, really quick, are you getting these steps? Or is it choppy for you, the video?

DR DELGADO: No, it’s fine.

DR KAHOOK: Apparently it’s just my computer. It’s the internet in Denver. Keep going.

DR RADCLIFFE: The reason the internet in Denver is slow is because everybody is busy tweeting about getting their vaccines now.

DR KAHOOK: That’s right. We do have the vaccines in-house. Keep going!

DR RADCLIFFE: What did I do? I’ll go back to that. So we’re right here. Okay. So the tube comes in. And I’m angling a little bit here. Always go bevel up. If I’m going into the sulcus as a plan, I might reverse it. And that depends on whether I think there’s vitreous in the sulcus or not. If I think there’s vitreous in the sulcus, I keep it bevel up. If I know that I did the cataract and there’s no vitreous, I’ll go bevel facing down to avoid the iris. I have viscoelastic in this needle. I’m coming in. You’ll notice I don’t make a paracentesis routinely, for my tubes. I’m coming at an angle here. And you’ll notice I can’t cross the pupil with this tract. And again, that’s if my tube does slide further in. It shouldn’t — and there I’m making your cut, Malik, that you described. I agree. Very useful. Now I’m getting lucky on this surgery. There’s no bleeding. No question why this one made the YouTube series. And so I usually use curved forceps. Sometimes I’ll use the Fechtner forceps to push the tube in. I would say this is about a 3.5 millimeter tunnel. But it will provide — you’ll notice it’s kind of hard for me to get it in. And watch what I do here. I’m gonna wiggle the eye by the tube. And that tells me: Nate, this tube ain’t moving. You don’t need to sew it with nylon. If that tube slid around, I would sew it. With nylon or vicryl. I agree, Malik. I use whatever gets me through the surgery with the fewest packages of suture opened. Now, believe it or not, the surgery is almost done. Here’s my pericardial patch graft. That’s gonna sort of provide a little blanket of safety. And now… Now, notice, this conj comes together so well. I have just cauterized the conj closed at this point. But we’re gonna put a few drops of the Tisseel glue. It has a thick and a thin. I think you’re supposed to go thick first. I don’t think it matters too much what you use. The thin kind of flows away fast. So it maybe gives you a little more time to act if you use the thick first. And it’s gonna stick together pretty well. But if you can actually get the conj to mate with the conj on the other side, it will heal even better, because the Tenon’s tends to be sort of a stubborn part. But here we have our closure. And now I’m gonna give a steroid antibiotic. And it’s amazing. Just 30 seconds or so after we close, the fluid from this steroid… I don’t show it in this video, but sometimes I’ll have it come over and elevate my recently glued area of conj. And it usually stays together through that challenge.

DR KAHOOK: How long do you actually squeeze the conj together to keep it in place postgluing? Do you hold it there for a count of five, ten, what do you do?

DR RADCLIFFE: I would say maybe ten seconds. Something like that.

DR KAHOOK: So when we’re doing these cases for the first time, trying to use this, this was a big debate that we had. Should it be a 30 second count? 20 second count? But I think 5, 10 seconds is more than enough. And you show that there.

DR RADCLIFFE: Yeah. The thing that will mess it up is active bleeding. If you have a tremendous amount of bleeding, there’s just too much fluid there. And the other thing is you should dry that tissue before you apply your glue. Ideally it is very dry. That’s when glue works the best. The times where I’ve had my glue fall apart were usually in hot eyes, neovasculars, where they were bleeding a lot, people on blood thinners, or if for some reason I was unable to get a dry field.

DR KAHOOK: Why don’t we show your video for clear path? And then after that, we’ll go to the question and answer. But go ahead, Maria, before we move on.

DR DELGADO: I had a question. When you mentioned that your conjunctival incision is 6 millimeters behind, is it because you need that conj to of course glue? I mean, you would not be able to do this at the limbus, right?

DR RADCLIFFE: I think that’s right. Actually, in one of the videos you showed, where you put your scleral patch graft down, my mouth started wearing, because I wanted to put glue… And it would have worked in that case. So you had a nice lax conj. But if you’re in a situation where the conj is tight, and there’s tension, glue can’t really overcome tissue tension. It’s just there to sort of keep things. And one of the things I have to say that you probably don’t is: I tell the patient you could undo my surgery by rubbing your eyes.

DR KAHOOK: So… Yeah. Just to be contrarian here, we actually — of course, my son is coming down here during the session, so he’s probably gonna come and say hi to you here. You want to say hi to Uncle Nate or no? He says no. Ha-ha! So we actually go at the limbus, Maria, and we do use glue and we close just fine. Instead of pinching the two sides together, we’re actually going — kind of where you put your suture that you did. And it works okay, but we do secure the plate to the sclera with suture. Which Nate doesn’t do. So it just depends on sort of how you’re mixing and matching things.


DR RADCLIFFE: Yeah. I agree, Malik. You can close the limbal wound. You can close a XEN, for example, with glue. But it’s nice to have something to pinch together. Malik is right. Going laterally and pinching is gonna work really nicely in that setting.

DR KAHOOK: Why don’t you show this video? We have a bunch of questions here. So after this video, maybe we’ll just go to sort of a lightning round of questions and answers.

DR RADCLIFFE: And the final thing I wanted to say is: I think you can sometimes get away with less prednisolone, if you glue. And patients may be less prone to rub, because the sutures do cause that foreign body sensation, and the glue typically is comfortable. So here’s the clear path. You’re gonna see a lot of the same concepts. And one of the important things — this eye has had some prior surgery. So I can see that looks like there’s been a vitrectomy. I see some scarring. And I’m of course…

DR KAHOOK: He does want to say hi, Nate. Sorry.

DR RADCLIFFE: Hey! How is it going, Zaid? It’s Uncle Nate! So this is all sort of very similar. I’ve got my clear path here. As I say, I think the toughest part is always tying this to be watertight. For some reason, it just gets me every time. Maybe I don’t suture enough in my daily life. You know, but… And then you test it here. Which I don’t think I show. But after you go ahead and occlude, you’ll take the 30-gauge needle, and you’ll make sure you can’t push any aqueous through at all. Even a slight drip is a problem. So I’m pushing it in now. And there’s a variety of ways to kind of taco the tube in. But it’s fine to fold in half. You know, it’s gonna be a tighter fit. Than the Ahmed valve. But we now have it back in that space. And I’m sewing. And that looks like… Looks like I am about 8 millimeters back. So I probably failed my test of coming forward too easily. So I put one stitch in. And again, I think — you just — everything is whatever the eye needs. Whatever it’s telling you it needs. You know, you can do. And here again, you’ll notice I’m coming across the AC. But this time in the sulcus. And I want to stop right here. This is the critical view. I have a needle that came in through the sulcus. And when you come in through the sulcus, you want to push your needle across the anterior chamber. And put the needle anterior to the iris on the other side. And that’s a great way to tell that you’re anterior to your IOL. If you can’t put your needle in front of the iris, it may be because your IOL is there. And you don’t want to come into the vitreous. I’ve had it happen once or twice in my career. And sometimes, by the way, you do make your needle in the sulcus. And your tube ends up in the vitreous anyway. Because remember, things can kind of change their course. They don’t have to follow the same track in. But this is just one little tip. Now, I can’t put viscoelastic in this chamber if I’m doing a ClearPath. Because it’s occluded, and I’m gonna have a high pressure. That to me makes things a little tougher. But here I am. I’m in the sulcus. I’m coming out. By the way, I do feel that the ClearPaths do very well in the sulcus. And that’s because there’s no flow, initially, and so you don’t have to worry as much about iris clogging. And everything is a little bit more stable at week seven, when that vicryl dissolves and the pressure comes down. Because… So you don’t get clogging of the iris in the tube quite as often. Here’s my patch graft. This looks like the New World product, which we have a nice scleral patch graft that New World Medical makes. Crimping it, so it stays forward. So that’s a double patch graft. And again, the closure is gonna be very similar. And I’m using vicryl I guess in this case because I have it. Maybe that conj looked like it was bleeding a little more than I wanted, and this is just a running closure. Taught to me by Celso Tello. Actually, it looks like I’m just doing two interrupted. Yeah.

DR KAHOOK: So Maria, I don’t think you have access to the ClearPath device at this point, right?

DR DELGADO: Not yet, not yet.

DR KAHOOK: So I remember sitting in an advisory board that was unrelated to glaucoma drainage devices, with Nate sitting on the other side of the room, and he had one of the models of the ClearPath when it was first released, and he was rolling it, sort of like you roll an IOL, and he was showing me how flexible it was. And I had a chance to work with New World on this device, when they were going through the development process. And that was certainly something that we wanted to do. Which was make it more flexible, so that it’s easier to get into places. But one thing that we’re seeing with this device, and I think, Nate, you’re seeing this too — is a smaller conjunctival incision, rolling it, and putting it through the conjunctival incision, and it opens up so you can make a smaller conjunctival incision, sort of like a Baerveldt.

DR RADCLIFFE: Almost like an IOL.

DR KAHOOK: Yeah, I would say from a postoperative standpoint, Baerveldt and ClearPath in my hands are about the same. There are some advantages intraoperatively that are real. But I know a lot of people listening don’t have access to the ClearPath at this point. But I think that’ll start to change as they start spreading it around commercially. So let’s take a little bit — thank you, Nate, for going through that. Let’s start going through some of the questions and answers here for the next 20 minutes or so, if you guys are okay with that. And I’ll start off here with this first question. Let’s see. If a patient has been implanted with an AGV, and has PAS with shallow AC, and the tip of the valve is in the AC, is small and touched iris, what do you do?

DR DELGADO: If I’m touching the iris, I don’t worry that much. If I’m touching the cornea, I do worry. If it’s a shallow chamber and you see that the tube moves, I will move it and put it in the sulcus. But touching the iris in general is not actually generally a problem. The problem is the endothelium of the cornea.

DR KAHOOK: You agree, Nate?

DR RADCLIFFE: I agree, and I will also say I’m shocked at how well the iris tolerates that tube touching it, pushing it aside. I don’t think I ever use steroids on a chronic basis in Ahmed valve patients, because the tube is causing iritis by touching the iris. I think it’s a never. It sounds crazy to me. But it just doesn’t cause the problem that you would think it would.

DR KAHOOK: So I like to leave the tube much longer, I think, than most surgeons do in the anterior chamber, and I go tangential. So the tubes that I put in have significant contact, sometimes, with the iris, for the course of that length inside of the anterior chamber. And I agree with Nate. It doesn’t cause any issues. Where it does cause occasional issues is if the tube is implanted in the sulcus, and there’s extreme sort of touching of the periphery of the iris. You can get a UGH-type syndrome with that. But anteriorly, I haven’t seen that. So next question… Should we mark — this is a good question that I haven’t actually seen on a session like this — should we mark the conjunctiva with a marking pen before cutting? Do you ever do that, Maria? Is there any reason to do that?

DR DELGADO: Actually, I never do it.

DR KAHOOK: Nate? You innately know what to do, so you never mark it?

DR RADCLIFFE: I eyeball it, Malik.

DR KAHOOK: Good. Thank you for that. When you’re first starting out, it’s okay to do that. If you’re teaching a resident or a fellow and they’re not sure how long to make that peritomy, err on the side of marking the conjunctiva. But it’s not precise. You can go a millimeter over and it’s not a big deal. I noticed with pediatric — this is the next question — patients when I use Ahmed valve, there is exuberant encapsulation after a few months, to the point where the bleb is palpable and visible at the supratemporal eyelid. Do you have any points to avoid this, or if it happens, what do you do? Encapsulated tube, let’s say it’s an FPA, pediatric model, for the AGV… Nate, let’s start with you. Do you do anything to avoid it, and if you do get it, what do you do? And maybe cross over between pedes and adults. It can cross over.

DR RADCLIFFE: It is felt that it’s the aqueous itself that’s causing that sort of capsule formation. Aqueous suppressants have been shown, if initiated early after the Ahmed valve, to help keep the pressure low and ultimately lead to better outcomes. So encapsulation to me is definitely an indication to start an aqueous suppressant, and to taper the steroid as quickly as the eye will tolerate. So if I see that at week one, I see a big bleb over my Ahmed, they’re back on fixed combination dorzolamide/timolol, aqueous suppressant, cut the Pred very quickly, and there’s an even crazier maneuver, which is: If the pressure is very, very high, you can do what’s called a serial tap of the bleb, where you put a 30-gauge needle into the bleb once a week for say five or six weeks, to try to decrease the tension on the bleb. Which should inhibit the remodeling that’s causing that big problem. I’ll tell you, this doesn’t seem to fix it all the time. But it’s something you can try.

DR KAHOOK: Okay. Maria, anything to add to that?

DR DELGADO: No, I agree, I agree. Probably when you see Professor Pankow talking about trabeculectomy, and all these — you don’t want these inflammatory aqueous, but also all that pressure going into these encapsulations, going in, you want to keep the valve functioning and the aqueous suppressants are key. And we use it very early in the post-op, most of the time.

DR KAHOOK: Okay. That’s great. There was a paper out of UCLA, by Law that came out a few years ago, that talked about starting aqueous suppressants early with the Ahmed valve. I think that is an underreferenced paper that everybody should read in training. And that’s one of the things that has increased the success of the Ahmed valve in our hands, with less encapsulation. If the pressure is over 10, postoperatively, get the patient back on their drops, keep the pressure very low for as long as possible, and you’re less likely to get the encapsulation. So that’s something to watch and see for the pediatric patients. If you’re getting these high teens, low twenties pressures, get them back on their drops, get the pressure down, less chance of encapsulation.

DR DELGADO: We were talking about the hypertensive phase. You don’t have to wait for the hypertensive phase. You can go before, just to avoid it, actually. I don’t want to go into a hypertensive phase.

DR KAHOOK: Yeah. One of my fellowship attendings used to say that hypertensive phase is the discussion you have before the discussion about failure.

DR DELGADO: That’s right.

DR RADCLIFFE: My line there, Malik, is: It’s not really a hypertensive phase. Sometimes it’s a hypertensive stage.

DR KAHOOK: Right, yeah.

DR RADCLIFFE: It is true.

DR KAHOOK: So we got a shout out from Rwanda, here, which is really nice to see. Thank you for saying hello. Next question. Do you have any other tips for the scleral sutures besides seeing the needle through the sclera? So what I think this is asking is: If you’re making your scleral pass with your suture, whatever suture you intend to use, how do you make sure you’re not going too deep? And you can also say how do you make sure you’re going deep enough? Is there anything, Maria, that you do to make sure that pass — which can be difficult with bleeding, no assistant, conj getting in the way — what do you do?

DR DELGADO: Yeah. First, get a good zoom. Zooming is great in this part of the surgery. You need to see well. You have your assistant with one hand probably moving the eye, if you need it, with the other eye, with the Weck-Cel, to make it clear that you have clear access, and you can do it slowly. You don’t have to go… All the way fast. But it’s difficult to know how deep you are. But this translucent — I don’t know. I just mentioned that if you see the needle, you’re sure. But also, you don’t want to go episcleral. Because then you have the suture in the episclera, and then of course, it’s not gonna actually fix the plate. So it’s of course practice. But make sure you’re in the sclera, not in the whole thickness of the sclera, and depending on if your patient has scarring, as I was mentioning, as far back as you go… Keep in mind that the sclera is thinner. So make sure that you use the right depth. I think the zooming and having the clear view is the most… The best tip, actually.

DR KAHOOK: I agree with all that. Nate, is there anything you want to add to that?

DR RADCLIFFE: No, I great.

DR KAHOOK: So question here that I’m interested to see what you think about this. Nate, we’ll start with you. What about vortex vein impingement by the plate? Is that something you consider when you’re doing the surgery?

DR RADCLIFFE: No, I don’t. And I’ll tell you… There’s just a lot of things that I somehow get away without knowing too much about. You know, and this — I put plates in all four quadrants. And I don’t really vary the technique any different from what you’ve seen. I agree, you can’t go as far back in certain quadrants. But I’m not doing anything special to avoid the trochlear muscle, for example, the superior oblique, I’m just… Putting tubes in and covering them up. So I don’t worry about any of that.

DR KAHOOK: Maria, do you worry about it?

DR DELGADO: Actually, no. Actually, no. To answer the question first. Actually, no.

DR KAHOOK: Go ahead and ask your question.

DR DELGADO: Never thought about it, actually. I don’t know. Yeah, my question was: Since we don’t have Baerveldts or now the ClearPath, we are always with the Ahmeds, and because of these encapsulations and cysts, sometimes, we prefer of course the superotemporal quadrant, and if that one is not good, or if we have to move the valve, usually we’ll go to the superonasally. But we don’t use most of the time the inferior quadrants. What do you think about that? How often do you use Ahmeds in the inferior quadrants?

DR KAHOOK: What do you do, Nate?

DR RADCLIFFE: Sure. I do typically go… Superonasal… So I go superotemporal first, superonasal, then I go inferonasal, and the last is inferotemporal. Because it’s the most exposed area. And you’re most likely to get an erosion. So I agree with you on that approach. Typically I’ll do… I used to do a superotemporal Ahmed and then a superonasal Baerveldt 350. And so you can go either style, in that order.

DR KAHOOK: I go superotemporal as first choice. If I have to do something else, I try to go inferonasal, with a ClearPath. Rather than putting a Baerveldt in that area. Just because — rather than putting an Ahmed in that area. The Ahmed being a little bit higher is more difficult to do inferonasally. And the really good thing about using either the Baerveldt or the ClearPath in that situation is you can more easily trim it, if need be. So you don’t have to go with the full 250 for either device. You can trim a little bit off just to get it in. Or — this is something that’s underutilized and might be controversial. You can do an FPA and do a pediatric plate in that area, where if you want something that’s valved, FP7 is a little bit more difficult to do inferonasally. You can do an FP8 in there and get significant IOP lowering. So the plate size thing — more, better. It’s actually controversial. I think if you’re getting around 184 to 250 for the plate sizes, then you’re probably okay. So next question here… We touched on this a little bit. Where can I place the glaucoma drainage device from the limbus to avoid optic nerve touch? And I’ll just start off by saying that following the label is really important. So 8 to 10 millimeters for the Ahmed. 6 to 8 millimeters for the ClearPath. Baerveldt is more similar. So 8 to 10 millimeters would be fine. Nate, do you do calculations before going in? I know you throw it back and hoping for orbital fat basically is what you’re saying.

DR RADCLIFFE: Yeah, and I want to make a comment about diplopia. I really don’t see much. And I’ll say… By much, I mean… Less than 1 in a thousand Ahmed valves will get diplopia for me. I have to believe it’s because I’m not sewing. And if you think about rubbing up against the optic nerve, I don’t anchor the plate down. So if the optic nerve wants to push it back forward, I think it can do that. What worries me is… You know, if you sew something against another thing, like a muscle, then I can see the double vision coming in. And so I think it’s fair to kind of consider that it might be okay not to sew some of these things into place. But most importantly, don’t ever put or suture a tube into a place it doesn’t want to be. Listen to what the eye is telling you. And if it’s not liking where something is, you know, there’s probably a reason for it.

DR KAHOOK: Yeah. I can say that for any procedure that you’re doing in ophthalmology. Not just tube surgery. So listen to what the eye is trying to tell you.

DR DELGADO: Absolutely.

DR KAHOOK: Really quick, there are a couple of things I’m gonna answer really quick to get to some of the others. Can the scleral patch graft be tied with vicryl? Absolutely. You can suture it down with vicryl no problem.

DR RADCLIFFE: And I just want to say: It’s a great idea to do that if you can, because I’ve seen erosions that were brought about by nylon. Nylon can be a source of erosion.

DR KAHOOK: Yeah. We do vicryl if we need something extra to seal. We do vicryl all the time for that. Do either of you double the — do you fold your pericardium, ever? To cover, or do you just do a single layer? Maria, what do you do?

DR DELGADO: Actually, we have just the sclera. It’s too thick. So we just use the sclera.

DR KAHOOK: Okay. All right. So… We’re getting more congratulations from Japan in this case. Can it be done without scleral patch graft under cover of partial thickness scleral flap? Do you ever do that, Maria, where you create a flap?

DR DELGADO: I actually don’t. But I have colleagues here that do a flap like a regular trabeculectomy, and they introduce the tube through that, so yeah. It’s an alternative.

DR KAHOOK: Yeah. There are many, many ways to cover tubes. And if you just Google it, you’ll see there’s technique of actually creating a full flap that’s vertical, that’s actually perpendicular to the limbus, rather than a tangential. So many ways to do it. I think Felix Gil — the Z formation going in, 4 millimeters back, is most of the time all you really need. How many hours after — should the eye patch be open after the surgery? How do you tell them to keep — this is a good basic question. After surgery, how long do you tell them to keep the patch on?

DR RADCLIFFE: Just a day. But I do a lot of surgery on monocular people. And if you can, you use just lidocaine instead of lidocaine bupivacaine, so they get their vision back if you’re blocking, and they can go home with a clear shield.

DR DELGADO: Same thing. I patch the eye after surgery. And I am the one who takes out the patch the next day, when I see them in my office.

DR KAHOOK: So somebody wants to know, Nate, how — this is a doubter. How long is your follow-up for your sutureless Ahmeds? How many decades?

DR RADCLIFFE: Yeah. It’s… You know, some of them are at 10 years. We published on I think one to two-year outcomes. What I will say in terms of all the ups and downs of that technique is I think you get faster healing. You don’t get much in the way of tube erosion. The biggest thing you’ll get is — you’ll sometimes get a tube tip that comes too far into the eye. If you catch that early, by the way, you can push on the plate, day one, or week one, and move the tube back. Because again, nothing is sutured in. And rarely, you’ll get a tube that slips out of the eye. Although I have to say, I’ve seen all of those things with sutured tubes.


DR RADCLIFFE: So I think again, if you really pay attention to the video I showed, which is on YouTube, Radcliffe-Ahmed, it’s all about wound construction and planning, and it’s a very reliable, safe, and efficient technique if it’s done with attention to those things.

DR KAHOOK: Yeah. I think both of you have social media presences. So for the audience, if you want to learn more about everything else that’s going on, that’s a really nice tool that we’ve been using more and more, during the pandemic. Just putting things on to help each other with education. Maria, do you use mitomycin for your tubes, ever?

DR DELGADO: Ever? Yes. Not often. But yes. I do. For example, in cases that have a lot of scarring, or neovascular cases, I use mitomycin in the sponge. Not inject it. I open the conj in the regular manner, and then in the sponge, I put the mitomycin C, probably 0.4 milligrams per milliliter. For four minutes. And I wash it and I do it… And I feel that it… Of course, I don’t have a study. We’ll have to do that. But I feel that… In some cases, it will help. It will help the fibrosis.

DR KAHOOK: Okay. Nate, do you use either mitomycin… Sorry. Go ahead. No, please, go ahead.

DR DELGADO: I was saying that some people also use them… And I don’t. I haven’t used them, but in the post-op, probably needling like you were mentioning, and injecting mitomycin C.

DR KAHOOK: Yeah. So there’s a study out of UCSF looking at that, and we’re getting more data. Some people have great success with using mitomycin. I don’t, but I’ve used anti-VEGF agents in the past. There’s a question on that. Nate, do you use mitomycin agents ever?

DR RADCLIFFE: I don’t. The only type of revision I’ll typically do is I’ll go to the operating room, I will cut off the capsule, and bring the conj back over. And I don’t do it often. I’m more likely to put in another tube. And that, I believe, has a 50% success rate. I’m thinking of a paper by Scott Smith from a while ago. So it’s not nothing. But I tend to revise Ahmeds more, when it’s a patient where I don’t think I have the real estate really to go with another tube. And after a failed Ahmed, I typically will go with a non-valved tube shunt, and one final thing I have to say — you can convert an Ahmed valve into a non-valved. You basically are just gonna take apart that plastic thing. And then you’re gonna remove those two little strips of Saran wrap-y material and you’re gonna have to tie it off with vicryl so you don’t get hypotony. It’s possible if you want a non-valved. And again, the reason to do that is you probably would get a slightly lower long-term pressure, but it will take 7 weeks to open, instead of the immediate pressure relief you get with an Ahmed.

DR KAHOOK: Right. That would be off-label. Just to be clear.

DR RADCLIFFE: That would be off-label.

DR KAHOOK: Go ahead, Maria.

DR DELGADO: I have also unroofed some of these Ahmed valves. Removing the capsule. And it tends to form again most of the time. So it’s not really very good.

DR KAHOOK: Yeah. So there are a couple questions here on anti-VEGF agents, and also on 5FU. We’ve used a ton of anti-VEGF agents for almost everything possible in glaucoma. Where anti-VEGF agents make a lot of sense is if you’re doing NVG, a case that’s of course a no-brainer. You can inject them in the clinic before you go to the operating room and have a much smoother course of a surgery. We’ve seen anti-VEGF agents work better with trabeculectomy or Ex-PRESS, remember than glaucoma drainage devices. In my hands, they tend not to work as well when you have a plate in place. Like Maria said, once you have the encapsulation, going and removing it, I haven’t had much luck with that either. It tends to reform. But very good surgeons who I trust do have success with it. So I think to each their own. There’s a question here about… Nate, really quick, how do you treat the viscoelastic in the anterior chamber with ClearPath? Do you empty that out at the end of the case?

DR RADCLIFFE: Ideally you never put it in. And then you don’t need to clear anything out. However, if you have bleeding, still the best way I know to stop bleeding in the eye is to fill the chamber quickly with viscoelastic, and then take it out five minutes later. So… But just keep in mind that you really don’t want to leave any viscoelastic, because you’re not gonna have any short-term pressure reduction, unless you’re doing something like needling a failed trabeculectomy and putting in a ClearPath in one surgery, which is not entirely uncommon for some of us.

DR KAHOOK: Yeah. There’s a question here — we’ll start off with Maria. What’s your philosophy on going in to do a tube in a patient who might have a shallow chamber, and also has a cataract? In this scenario that the questioner is asking, it’s an NVG patient. Do you combine phaco with your GDD frequently? What’s your decision making in that scenario?

DR DELGADO: I tend to worry first about the pressure rather than the cataract. So if the pressure is very high, probably I would like to manage the pressure first and don’t go into an NVG patient with a cataract to do the cataract. But if possible, I would love to do them both. I will try to solve the problem. Because then we will have a patient with a dense cataract, which is going to get worse, and then we have to go into the surgery, and that will maybe affect our implant or our functioning of the bleb of the valve. So I will try to do combined surgery, yes.

DR KAHOOK: What do you think, Nate? Do you combine?

DR RADCLIFFE: Yeah. I do, particularly with Ahmed. But I can tell you that the cataract has no impact on how well the valve will work. Valves work as well as valves work, period. It’s hard to find anything — ECP, micropulse, goniotomy — it’s hard to make a valve better than it already is.

DR KAHOOK: So I’ll just add that I think the best glaucoma surgery is cataract surgery. So in my opinion, almost everybody who has glaucoma should go for early cataract surgery. Because your care is much easier. Your options expand dramatically. So two questions that are related, and maybe we can touch on these quickly here in the last few minutes that we have. Maria, do you ever put the tube or the plate supra-Tenon’s? Or do you always go infra-Tenon’s with your implants?

DR DELGADO: I know my dear friend George Tanaka’s supra-Tenon’s implants. No, I haven’t done it, but I think it’s smart, and it’s probably a nice way to deal with some things. But I don’t have experience with it.

DR KAHOOK: Yeah. Nate, have you played around with it? There are a lot of posts on AGS-net, Friedman, Tanaka, talking about this. They’re both excellent clinicians and I trust both of them. Do you do it?

DR RADCLIFFE: I guess if I were gonna do it, I would be more likely to just do a tenectomy than to try to fiddle… It’s not the easiest space to get into, with a good dissection. So I would be more inclined to just kind of get rid of the Tenon’s above my tube. And try to thin things out that way.

DR KAHOOK: I agree with that. I don’t do supra-Tenon’s. But I have removed Tenon’s when it’s thick or if I’m worried about it. There’s a question here about what do you do with a scleral buckle in place. What’s your technique? Let’s say you’re going to do glaucoma surgery. And there’s a buckle in place. What’s your decision making in that case? Maria, without being married to one device or the other, what do you think?

DR DELGADO: Yeah, right. I usually leave the buckle in place. I try to put the implant on top of the buckle. And if I see that it’s very hard… I talked about this with my retina colleagues. And they say if you can, you can cut the little piece. But I don’t want to cut — I don’t really want to cut it. But I think I have managed with putting the plate on top of the buckle.

DR KAHOOK: You too, Nate?

DR RADCLIFFE: Yeah, and in fact, one time I did an Ahmed valve and I didn’t even realize the patient had a buckle underneath. So the bottom line is: If you sort of stay a little higher, maybe almost supra-Tenon’s, you’ll in fact be able to just coast right over it. You’ll notice extra scarring, but everything else can kind of be the same.

DR KAHOOK: Yeah, just a couple of additions. Sometimes you can actually suture the eyelids to the buckle. So it kind of — it’s a platform for you, right there, that delineates exactly where the plate is gonna sit. And buckles are amenable to a needle going through. So easy enough. There’s also the Schocket procedure where you can take a tube and put it into the capsule that’s formed by a buckle itself, so that’s your plate. The buckle itself becomes your plate. You can just kind of open up the capsule around it and sneak in a silicone tube, and it can be like the Ahmed extension tube, that is separately packaged, so there are many ways to do it, but it doesn’t prevent us from doing the surgery when a scleral buckle is present. So some questions about sutures that we’ve already answered. Can we use the Baerveldt if there are large prolene sutures at the equator? Post-VR surgery? That’s kind of the same question as a buckle. So if there’s something there, we can always work around it. What tube should we prefer in a case that has undergone a band buckle? Would you pick a Baerveldt over the Ahmed in that case, Nate? Or would you still go with the Ahmed, if the buckle is present?

DR RADCLIFFE: You know, this brings us to a better, more direct way to ask that question. Which is: How do you choose in general? And for me, I choose an Ahmed valve when the pressure is dramatically out of control. And when 7 weeks is too long to wait to get the pressure down for the health of the nerve. And I choose ClearPath or a Baerveldt when I’ve got time and I need a lower target. And so depending on that patient’s situation, I would make the same choice.

DR KAHOOK: Okay. Do you feel the same way? Maria, what do you have access to?

DR DELGADO: Ahmeds. Ahmeds.

DR KAHOOK: Okay. I think it’s really important to state: There are many, many options right now, around the world. In the US, we basically have ClearPath, Baerveldt, Ahmed, and Molteno. Outside of the US, there are several others that are in from… There’s the Paul device, there’s a couple of others. There’s the Aurolab device. So I think a lot of these depend on your experience and sort of what you’re comfortable and in many cases how you were actually trained. So let’s do one more question here. Nate, do you use a rip cord? And how do you decide whether you use a rip cord or not?

DR RADCLIFFE: I don’t use one. I’ll let you kind of speak to that. If I’m interested in shorter term pressure reduction, I will try something like micropulse, with my ClearPath. But I haven’t had good experiences in training. With rip cords and things like that. So I’ve stayed away from it.

DR KAHOOK: Okay. And Maria, you said you use the AGV primarily? So you don’t use a rip cord, of course, because of that? So the rip cord primarily is with the non-valved… And also, I used it during fellowship, and maybe for a year afterwards, and realized that it really doesn’t have a role in my practice. So I’ll do Sherwood slits in my non-valved devices. And that tends to help with control, postoperatively, and tie it off, but that’s also a little bit of voodoo. How big the slits are, how many you do, do you use a needle or some sort of a blade. Unfortunately I don’t want to end here by saying a lot of glaucoma surgery is voodoo. But it is. We know that. A lot of what we do depends on our experience, our practice, who trained us, but more and more, with a lot of these new devices, whether they’re MIGS devices or these new valves that we’re getting our hands on, it’s becoming more repeatable, reproducible, and our technique is also becoming more refined. I’m always excited to have a session like this, where we can have an open discussion about our techniques. Maria, this is the first time you and I have been on a session like this. I was excited to do this, I certainly learned a lot, and I hope we can stay in touch and share notes on this, and maybe do a session like this in the future. Nate, I’ve had more than enough of you. So this is probably the last time that we’ll do a Zoom together. But I think your teachings — the audience is out there. If you want to see some unique and innovative techniques, if you go to Dr. Radcliffe’s YouTube site, I encourage you to sign up for his YouTube channel, and I also want to encourage you to go to Cybersight, look at the educational resources that are there. We have kogt.com on the Cybersight library, and please reach out to me on Twitter or Instagram, and let me know what you want future point to point sessions to cover so we can make this better. I want to thank Maria and Nate for your time, I hope you have a great rest of your day, and thank you, everybody, for attending. Thank you, guys.

DR RADCLIFFE: Thank you, Malik.

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December 17, 2020

Last Updated: October 31, 2022

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