Lecture: Glaucoma Drainage Devices & Managing Complications

This live webinar will describe the basic technique of GDD implantation with tips on how to handle the intraoperative difficulties in complex cases with the help of video demonstrations. The webinar will also cover the management of common complications like over filtration, tube erosions and tube retraction with case examples. By the end of the webinar, the participant will be well acquainted with the basics of tube surgery and will learn to manage postoperative complications on their own.

Lecturer: Dr. Suneeta Dubey, Head of Glaucoma Services, Dr. Shroff’s Charity Eye Hospital, India


DR DUBEY: Hello, everybody. I’m Dr. Suneeta Dubey from New Delhi. Thank you for joining. It’s exciting to see so many participants joining from across the world. So today, I’ll be speaking about glaucoma drainage devices. Basic techniques. And I’ll also be touching upon the management of common complications which you encounter commonly. I’ll get you through a series of cases with practical tips, which will surely help you in your practice. And at the end of the session, I’ll go through some of the questions, so please keep your questions posting on the Q and A box. I am thankful to Orbis/Cybersight for this wonderful platform. For giving me this opportunity. So I am going to share my screen now. And in between my talk, I’m going to ask some poll questions. Just to assess your understanding about the topic. So I’ll start with this poll question. Which tube implants do you prefer to do in your practice? Valved implants, non-valved implants, both, depending on the situation, or you do not perform implants at all? So you will have 10 to 20 seconds to answer this question. Okay. I’m glad to know that most of you are performing tube implant surgeries. And so that will be very helpful for me, to make you understand. So let me get started now. So, as we know, tube implants are a viable alternative, and they’re gaining popularity with better designs, material, and techniques, which significantly improve their long-term outcomes. So there are a variety of tube implants which are available across the globe. But in India, we are using AGV extensively, and also now the AADI implant, which is a non-valved implant. It is very, very cost effective, and very good to use. And it has not been just used in India extensively, but also in many other countries. So I will mainly be talking about the AGV and AADI, and we don’t have ClearPath, which is the latest addition in the category and which is a non-valved AGV. So as we know, these are the primary choice for most inflammatory glaucomas, be it neovascular glaucomas, glaucomas associated with syndromes, post-surgery glaucomas, or in patients who need second surgeries or treatment surgeries, they are the primary choice. Also with the promising results of our DVD study, the use is increasing even in primary glaucomas. It’s very, very important to meticulously plan your surgery. And do a proper preoperative evaluation. It’s important to take proper history and assess the patient for uveitis, neovascular glaucoma, previous surgeries, conjunctival scarring, presence of scleral buckle, or squint surgeries, as they can alter the position of the masses, and they also affect the type of implant and the site of implant choice. So the type of implant will depend on the clinical diagnosis and the surgical site. Superotemporal is the preferred site for the obvious reasons that it is very easy to perform surgery in the superotemporal quadrant, and there is lower incidence of ocular motility disorders. And lower incidence of erosion of the implant. However, if the eye has undergone multiple surgeries, it is important to choose the quadrant which has minimal scarring. Also, since most of these eyes have undergone multiple surgeries, the conjunctiva may not be good enough. So be prepared to use autologous or exogenous grafts. Proper placement of the tube is very important for better long-term outcomes. And therefore it’s important to assess the extent of PAS and status of lens, which are important determinants of position and placement of tube. Also, since most of these eyes are associated with comorbidities, it’s important to manage the primary pathology, as they can lead to postoperative complications. If the eye has vitreous or synechiae or inflammation, you have to first manage that before planning for implant surgery. Now I’m going to show you the basic technique of an AGV implant. It’s very important to have good exposure of the surgical site. So you can use a corneal transaction suture or a superior (inaudible) suture or both. In this case, I have used both for very good exposure. The conjunctival flap can be limbus or fornix-based. In most of my cases I make a limbal-based conjunctival flap, since it is easy to make and the exposure is also very good. If you have fibrosis close to limbus, then you can go slightly posteriorly. It’s important to dissect deep into the fornix. So as to create room for the placement of it. I always measure it. It should be 8 to 10 millimeters from the limbus, depending upon the quadrant. Priming of the AGV implant is very essential. Because if you don’t prime it, it may not work. And it is better to have a stream, although you can also have just a trickle. You should not reject the device if you just have a trickle. When you insert the device, you have to keep two or three things in mind that are very important. That you do not hold the device at the valve area. You can damage the valve area. And the device should not keep popping out. If it keeps popping out, that means you are not under the Tenon’s capsule. And you are maybe over the Tenon’s capsule. And once it is in position, you sutured it with the help of either 9-0 nylon suture or 8-0 nylon suture, depending upon the availability. But you have to use a non-absorbable suture. You can just rotate the knot of the suture into the eyelid, so as to avoid erosion in the postoperative period. Now, coming to the very crucial step of insertion of tube, the tube can be placed in the anterior chamber. With a pars plana — but it’s important to — here I’m creating the scleral bed so the tube fits into this bed, and doesn’t move here and there. So you have to cut the tube in a manner that 2 to 3 millimeters of it goes inside the anterior chamber, with the bell up, if you’re planning to put it in the anterior chamber. And then the 23-gauge needle — you go inside the anterior chamber. And insert the tube. Into the anterior chamber. So you can see the tube is in position. And then you have to fix the tube with the help of this mattress suture, 9-0 nylon, so that it doesn’t move in the postoperative period. It fits snugly onto the sclera. So once you have put this suture, you have to cover it up with the scleral patch graft. We have availability of scleral patch graft. So we cover the tube with the help of scleral patch graft. There are various ways for insertion of the tube. You may not necessarily use the patch graft always. But it is better to use it. And once you have covered the tube with the scleral patch graft, you close the conjunctiva. As you can see here. The advantage with the limbal-based flap is that you can take a bite of the episclera. For better anchoring of the sclera. With the limbus. So at the end of surgery, your AC should be well formed, the tube should be properly placed, and there should be no leakage. In the absence of scleral or any patch graft, you can also use this scleral flap, and you can insert your tube inside this… Under the scleral flap. As you make the scleral flap or trabeculectomy in a similar way. Although it has to be slightly larger. And then you insert the tube, and then suture the scleral flap. Another way is to make a scleral channel, as you can see in the video on the right side. They are very old videos. Now I no longer use these techniques. So you are making the scleral tunnel. And you are coming out on the other side. And then inserting the tube through this tunnel. And then into the anterior chamber. So if you don’t have patch grafts, you can use these techniques. You can also insert the tube in the pars plana. I’m going to show you this patient. Of chemical burn. Where we planned a tube implant with K-pro. As you can see, the cornea was vascularized and heavily scarred. So after implantation of Kpro, here, as you can see here, you insert the AGV plate in one quadrant, and do a proper vitrectomy. If you’re planning to put the tube in pars plana, the vitrectomy has to be complete. It has to be complete pars plana vitrectomy. And then you can insert your tube from one of the ports. The port which you have made in the superotemporal quadrant. So you don’t have to make separate port. And then this is the end of surgery. So at the end of the procedure, you should be able to see your tube through the pupillary area. Then you have put it in with this. The insertion of tube through the scleral tunnel is getting very popular nowadays. And it is because the chances of tube extrusion are pretty less when you use a long tunnel. Maybe 4 to 6 millimeters posterior to the limbus, you start with the tunnel. Make the tunnel with the needle, and insert the tube through it, and you don’t even need a patch graft when you’re making a tunnel. Now, coming to the implant, which is again commonly done, there are some differences between the valved and non-valved implants. Here the conjunctival flap is larger. Since you have to move the muscles, the flap may be better, because you have to identify the muscles, and it will make the identification of the muscles easier. As you dissect into the fornix, you try to isolate the muscle. You can use muscle hooks. Two muscle hooks. Or you can use the muscle hook I am going to show you. These are the radial incisions. Pretty large conjunctival flap, as you can see here. So this is the muscle hook. Which has an eyelet, and where you can use a 4-0 silk suture around it. And as you loop around the muscle, you can pull one end of the suture to separate the entire muscle. As you can see here. Especially when you are a beginner, you can use this technique, and this will help you to isolate the muscle properly. Put your implant behind the muscle. And even give retraction. Through these sutures. So this is the AADI implant, as you can see. It’s a flexible implant. So you first introduce one end, or one wing under the lateral rectus and then another wing under the superior rectus. And then suture it as you would do for the valved implant. Another difference is you have to ligate the tube so as to prevent hypotony in the early postoperative period. So here I am just fixing the tube with 9-0 nylon suture, as you can see here. And here I am putting ligation, a ligature, around the tube. The 6-0 vicryl. You can use 6-0 vicryl or 7-0 vicryl. And ligate it tightly, so that there is no flow of fluid to the tube. So I have put two ligature sutures here. And then I am just checking by injecting fluid. There should not be any flow of the fluid. You can just see this air bubble is coming back. And the rest of the procedure is the same. You have the venting slits to facilitate egress of liquid in the early postoperative period. You can just give two or three venting slits into the tube. And then rest of the procedure is the same. There are a lot of patients who require combined surgeries. So it has now become a common practice to perform phaco with tube and IOL in my practice. And this is one patient who was one-eyed. The other eye, as you can see, was PR accurate, and he had concomitant scarring with very high pressures, as you can see here. The pressures were in 40s and 50s. I planned phaco plus IOL with AGV in this patient. And first the PK was done. So after the PK I planned the phaco with AGV in this. The temporal incision was made. The phaco was performed, the superotemporal quadrant was chosen for placement of the implant. The procedure was more or less the same. You can see the tube is placed in the sulcus. You have to put a lot of visco to expand the sulcus so you can put the tube in the sulcus, under the IOL and over the iris. You can see here. And the rest of the procedure is the same. So this is the postoperative picture. The tube is nicely placed in the sulcus, as you can see here in both of the pictures. The pressure is well controlled after the combined surgery. IOL plus tube. And the vision had also improved. So now coming to another poll question, which you have to answer. The question is: Tube can be performed as primary procedure in situations… When intraocular surgery is needed for another ocular condition. Patient cannot come for frequent follow-up. In eyes with inflammation and neovascularization. In patients who are contact lens dependent. And the last choice is all of the above. Okay. So excellent. I think for most of you, the answer is correct. The answer is all of the above. So tube implants can be performed, as I said earlier, in situations when the patient needs multiple surgeries. When the patient cannot come for treatment follow-up. Especially with valved implants. Because you do not need so much of care postoperatively, as you would require in trabeculectomy. And with eyes with inflammation and neovascularization, obviously implant is first choice, because the results with trabeculectomy are not so good. In contact lens dependent patients, since the bleb in the trabeculectomy is compromised, trabeculectomy is not indicated. So in all of these procedures, implant will be the procedure of choice. Now, as you see the patient the next day, you may see a little bit of hypotony. As you can see in this picture, there will be diffuse edema and congestion, and there will be some vessels over the episcleral plate. And in valved implant, you may see hypertensive phase with rising IOP. As you can see here, the bleb appears raised, tense, and distended with aqueous. However, during the stable phase, which is achieved over 3 to 6 months, you will see this well circumscribed thick walled bleb. So hypertensive phase — if the AC is well formed and there are no other complications, you can just observe. Just keep the patient on topical steroids and cycloplegics. You don’t have to do anything unless there’s tube corneal touch or lens corneal touch. Hypotony is more common in the case of valved implant initially, but later on, with non-valved implant, when the tube opens up — and it is also common in patients who have inflammation for either cyclitis, ciliary body shutdown, so you have to be very careful with these eyes. It is more common in myopic and buphthalmic eyes. Hypertensive phase is very common in patients with valved implants, and it can happen as early as 2 to 6 weeks. The cause is early exposure of the conjunctiva and Tenon’s capsule to aqueous with proinflammatory cytokines inducing early fibrosis and scarring. Also the biomaterial and the consistency of plate are the contributory factors. So in the initial phase, you don’t have to do much. You just have to start aqueous suppressants and steroids with digital massage. And if the condition doesn’t resolve in time, then you have to do the removal of the cyst wall or bleb needling, but the results are not very good. You may need to revise the surgery with another shunt. So this is the patient. Typically you can see the bleb is getting denser and denser and elevated. And this is the congested, raised bleb. This is another patient, which I operated recently. So this patient underwent multiple surgeries. Cataract surgeries, glaucoma surgeries, so his conjunctiva was very scarred. And I did tube implant in him, because the pressure was not controlled on maximal medical therapy, and AGV was done. So initially the bleb was well formed. But later on, one month postoperatively, you can see the bleb which is so encysted — you can even see this bleb from a distance, like a protrusion in the superotemporal quadrant. So for high tension blebs, what you can do is that you can just tap the bleb using 30 gauge needle. On slit lamp. Serial taps may be required. And the logic behind these taps is that it may alter remodeling of the bleb. And can result in hypertensive phase. However, the results are unpredictable. It is a very simple procedure and can be tried on slit lamp in the office. Now coming to another question. Which of the following statements regarding hypertensive phase is false? Hypertensive phase is seen because of cytokines in inflamed aqueous in early postoperative period. More common in valved implants. May get resolved with use of steroids and aqueous suppressants. Commonly seen in eyes where tube implant is performed as primary glaucoma surgery. So 50% of you are correct. The answer which is not correct is that it is commonly seen in patients where the tube implant is performed for primary glaucoma surgery. So the rest — all the three statements are correct. Now coming to complications. So complications can occur during early, early postoperative period. They can be valve related. As hypotony or hypertensive phase. As we have discussed. There are unique set of complications, which are related to the design of tube implants. And outflow obstruction, conjunctival erosion, implant exposure, tube migration, or diplopia. Or they can be related to surgery. Like corneal decompensation, endophthalmitis, vision loss, or surgical failure. So complications can occur even after trabeculectomy. So these are common complications which can be seen in the early postoperative period. Like blockage of tube because of blood. Or iris or vitreous. Tube corneal touch and corneal decompensation can happen over a period of time. And the implant extrusion is pretty rare. Though tube erosion can be seen in some patients. So outflow obstruction in early phase could be because of blood, fibrin, iris tissue, lens material, or vitreous. Some of them may be transient. They can respond to topical steroids and cycloplegics. Blood and fibrin can retract with topical steroids and cycloplegics. Iris strands and vitreous strands can be managed with Nd:YAG laser. And in some of these patients, surgery may be required if they are not responsive to these therapies. This is one of my patients with neovascular glaucoma that I did tube implant. And as you can see here… One strand of the blood, which is going into the lumen of the tube, causing raised intraocular pressure. So by just using low energy at the tip of the tube, you can cause retraction of the clot. The clot will just pass through the tube. And you can get the clearance of the tip of the tube, as you can see here. So this is a very simple procedure that you can do. Another patient who has a history of trauma three years back, and he had inferior RD, he presented three years later, the PR surgery was done, the patient had very intractable glaucoma after doing PR surgery. Initially there was pupillary block, we did YAG laser, but it was not successful. Followed by silicone oil removal, then transscleral cyclophotocoagulation was done. However, after a few weeks, the pressure again rose, so I planned phaco with glaucoma valve in this patient, because the patient developed cataract. However, because of sudden hypotony, there was bleeding in the anterior chamber, and you can see this tube getting clogged by blood. Didn’t respond that much to conservative treatment. And then again, YAG laser was done in this area. And you can see the lumen of the tube clearing up. So it’s a very simple and effective procedure. Another patient who had a history of trabeculectomy in early infancy, so it was a case of congenital glaucoma, and both eyes, trabeculectomy was done somewhere else. And then he presented to us — his pressures were very high. So there was failed trabeculectomy, there was flat bleb. So I decided to do AADI implantation in this particular patient. I think you should introduce the tube — away from the cornea. And sometimes it touches the iris. Although it doesn’t make much of a difference if you’re close to the iris. But sometimes iris can get incarcerated. Into the tube. And again, very simple procedure. I just gave two or three shots with the YAG laser over here. At the tip of the tube, where the iris was incarcerated. And you can see this incarceration was relieved. And the tube has cleared of iris. Another patient who had history of trauma, there was no obvious vitreous in the anterior chamber. When I performed tube implant. But on third or fourth postoperative day, you can see here the tube got blocked by the strand of vitreous which appeared to be coming from behind the lens through the zonular dialysis. So since it was not possible to cut this strand, this was a thick strand, it was not possible to cut this strand with the YAG laser, we performed limited anterior vitrectomy and pulling the vitreous tag with end gripping forceps helped in clearing the vitreous from the lumen of the tube. Now coming to second very important complication, which is very specific to the tube implant surgery, which is conjunctival erosion, or the tube erosion. It’s very important to manage this complication properly, because it poses a risk for endophthalmitis. So conjunctival tube erosion — there’s a difference between tube erosion and wound dehiscence. Tube erosion is defined as any exposure of the tube after one month of surgery. If it happens before one month, in the immediate postoperative period, it is called wound dehiscence. You can see here this is the wound dehiscence. This wound dehiscence could be managed with topical steroids and lubricants and systemic doxycycline. It may have antiinflammatory activity, along with improved ocular surface, frequent lubrication, this conjunctival dehiscence was reepithelialized completely in two weeks. So why does tube exposure occur? It is because of the excessive tension overlying the tube or immune mediated inflammatory process. So there is an ischemic damage to the conjunctiva. Or repeated mechanical force caused by eyelid blinking. So eyelid blinking just rubs the conjunctiva over the tube, and if the conjunctiva is not in a very healthy state, like if the patient has undergone multiple surgeries or the patient is an immunocompromised patient, like diabetic, or a patient is having some hormonal changes, then such type of complication can happen. It can be prevented by using long scleral tunnel, as I had shown earlier. And if the tube is in the sulcus, or if the tube enters the eye at 12:00, rather than 10:00 or 2:00, there are less chances of exposure. So the tube should enter the eye. And if it is slightly… It is not straight. It is slightly deviated on one side and enters at 12:00 position, then the chances are less. So suturing the tube to the underlying sclera makes the tube flatter. Hence less friction with the overlying patch graft. So it’s important to suture the tube onto the sclera, and also covering the tube with the patch graft. If you have made a tunnel, it is very tightly fitted into the tunnel and it is flat onto the sclera. So prior to suturing, also to prevent the immunological rejection, it’s important to clean the donor scleral patch graft, abrade all the iris tissue, as it can lead to reaction and inflammation. In high risk patients, additional techniques can reduce the risk of exposure, as I have explained. So what do you do with erosion? You have to dissect the conjunctiva, fix the tube to the scleral bed, put the patch graft. I am going to show you the video. And if the conjunctiva is in a good state, if it is not necrosed or avascular, then you can just do conjunctival advancement. If the erosion is small. And you can also use conjunctival free graft or autograft if the conjunctiva is not healthy. Or you can use pedicle graft. So pedicle graft basically is from deep into the fornix. It allows importation of distal vascularized tissue to the sclera, to the area. So if the conjunctiva at the site of erosion is necrosed and scars, then you should use pedicle graft or a free conjunctival graft. So as you can see here, you have to just dissect the conjunctiva. Secure the tube in place. Or the graft. Any kind of patch graft over it. And then suture. So I’m just going to show you this patient, who was referred to me by some doctor. And there was exposure of the scleral patch graft here. I decided to do the suturing. The repair of it. And when I opened the conjunctiva, I saw that the plate was sutured horizontally, and the tube is quite short here. So I think it was the cut, the positioning. Since there was no availability of the AGV implant, I decided to put the same implant, after cleaning it properly. And then introduce the tube. And since the conjunctiva was short, simple technique is… So very simple technique is to… Just show you again. So you just give an incision… Into the conjunctiva and not in the Tenon’s capsule. Just to bring it forward. Make it more mobile. And then use tissue glue, which sticks the conjunctiva well onto the scleral patch graft. However, one has to suture it… So as to be doubly sure that it doesn’t retract. And then over it, the amniotic membrane. Which is again freely available to us. And it helps the regeneration of conjunctiva. So this is another patient who was referred to us from elsewhere. For RE tube repositioning. And there was tube exposure, as you can see here. The tube repositioning was done with AMG and patch graft. In 2019, and again in December 2020 there was tube exposure. So as you can see, there was tube exposure at 12:00. So we’re just assessing the status of conjunctiva. Just dissecting it. So just dissect the conjunctiva. So that later on you get enough conjunctiva to suture back. This patient had cataract also. But we decided to just do the repair. In one sitting. So the tube was removed from the anterior chamber. Earlier I thought of removing the implant. But then… Decided to put it at a separate site. So just cleaned it, and then made another track on the temporal site. Inserted the tube. So the tube had enough length. It was two to three millimeters inside the anterior chamber. It was sutured. And then the scleral patch graft, which would cover the previous track also… And we have this eye bank, so we have the tissue with us. So we just cut the patch graft to the required length. And just made it half thickness. And then sutured it. It is not… And then we suture the conjunctiva over it. As you can see. Here we separated the Tenon’s and the conjunctiva. And the conjunctiva was short. So the Tenon’s capsule was covering the scleral patch graft. And the conjunctiva over it. Since conjunctiva was short, we decided to use amniotic membrane in this particular patient. So this is the amniotic membrane, which has been sutured all around. And then over it, a contact lens was placed. So the patient is doing well. It was done almost six months back. So this was the repeated exposure. And this is the post-op picture. So this is my last video. So this was a patient who, again, underwent multiple surgeries. She had uveitis, and the patient had multiple grafting done. And then she developed glaucoma. And she also underwent limited transscleral cyclophotocoagulation, before the implant surgery. So she presented with chronic hypotony, delayed hypotony. When she came to me, her pressure was just one or two millimeters of mercury. And that was a chronic hypotony with macular striations. And so first I decided to form the anterior chamber with Healon GV, but that didn’t help. And then I decided to do the intraluminal tube stent. With the help of the 4-0 prolene suture. Which is a very well described technique. And this is a simple procedure. And it’s not very invasive. Because you don’t have to deal with the implant. What you do is you just make a corneal stab incision. With the side port. Inject dye with Healon. Make another incision. And then introduce this 4-0 prolene suture in the lumen of the tube. Graft the tube with the help of microforceps. Which I use in the retina surgery. And then… Cut it. And then suture it. And at the end of surgery, the pressure was okay. Although 4-0 prolene suture would not reduce the aqueous flow completely. Because it blocks the outflow basically by 60% to 65%. 3-0 prolene suture is a better choice, but then it is very difficult to thread the tube with the 3-0 prolene because it is thick. So 4-0 prolene, if you are able to reduce the outflow facility by 60% to 65%, that should be good enough in most of the cases. So this patient still has hypotony, but not that much. The pressure has now increased to 6 to 7 millimeters of mercury. So coming to the last poll question, which of the following statements is false? Tube implant patients do not require frequent follow-up. Valved implants have to be primed. Tubes in non-valved implants need to be ligated. Patch graft is mandatory to cover tube in all cases. 22, 23, 24, or 25 gauge needle can be used to make entry track for tube. So you have to answer it in 20 seconds. So the correct answer is: Patch graft is mandatory — the false statement is: Patch graft is mandatory to cover tube in all cases. It is not required if you are making a tunnel. You don’t require to put a patch graft. And the rest of these statements are true. Valved implants have to be primed, as I said. And non-valved implants have to be ligated. And you can use 22 gauge needle, 23 gauge, or 24 gauge needle to make the needle track, or even 25 gauge in patients who have very low scleral rigidity. 25 gauge needle can also be used. So to conclude, it’s important to do a meticulous examination, pre and postoperatively. Follow up your patient. Look for hypotensive phase and hypertensive phase. And especially if you have used a non-valved implant, at the time of ligature release, there can be sudden hypotony, flat AC, and inflammation. Which you’ll need to take care of. You’ll have to communicate with your patients. You’ll need to tell them about the hypotony, that they may get reduced vision, or the pressure may reduce, at the end of one month or six weeks. So you need to educate the patient about non-valved implants. Recognize the hypertensive phase. And nowadays, the routine practice is to give aqueous suppressants — to start them on the initial phase when the pressure is beyond 10 millimeters of mercury. So you don’t have to wait for the hypertensive phase. You have to start aqueous suppressants before that, and that drastically reduces the hypertensive phase. Look for the development of complications, especially in high risk eyes. And you have to perform surgery meticulously. And early recognition of complications is the key to improve success. Thank you very much for your kind listening. Now I can take up the question answers. I’ll just stop share. So one question is: What is your favorite site for secondary implant? So as I said, the first choice is superotemporal quadrant. However, it depends… You have to choose the site of least scarring. However, most of the time, it is possible to use the superotemporal quadrant. My second site choice is superonasal. And then I go to inferonasal and then to the inferotemporal. Inferotemporal is not the preferred quadrant, because it has more chances of tube exposure, and it is difficult to perform surgery in the inferotemporal quadrant. Do you use mitomycin C during shunt surgery? I think it’s a very good question. Most of the earlier studies didn’t show any advantage of using mitomycin C. But now the latest studies are showing that mitomycin C improves the success rate. Especially in eyes which have scarred conjunctiva. And in studies that have used mitomycin C as injections, so at the end of surgery, you can give 0.4 milliliters into the bleb and repeat it in the clinic at one week and one month. So the success improves almost by three times, by use of mitomycin C, although I do not have any personal experience of use of mitomycin C. But it can be used. So another question is what suture did you use to isolate the muscle during AADI? So I used 4-0 silk suture. The suture is passed with the eyelet in the muscle hook. Retina surgeons frequently use these kinds of muscle hooks with the sutures in the eyelet. And it helps them to retract the eye, as well as isolate the muscles completely. So what are the indications of pars plana tube implant? So as I said in my practice, I do not often use pars plana insertion of the tube. Because most of my tube insertions is in the sulcus. Especially if the patient is pseudophakic. Or if I perform it with phaco, the AC is deep, and I can put it in the anterior chamber or in the sulcus. But in patients who are undergoing pars plana vitrectomy for any reason, in patients who are more prone to chronic endothelial damage, and who are phakic, you can use it in pars plana. But then you have to have a team of retina — you have to have a team. You have to have a retina surgeon along the team. Who can perform complete pars plana vitrectomy before you put the tube into the pars plana. And we do a lot of Kpro in our hospital. And in Kpro, mostly they prefer to do complete vitrectomy. So in that case, the site, preferred site, is pars plana. Another question is: How much posteriorly do you insert tube for sulcus placement? So how much posteriorly do you insert the sulcus? If you’re placing the tube in the anterior chamber, then it should be 0.75 to 1 millimeter. If you are putting the tube in the sulcus, it should be 1.5 millimeters, and if you’re putting it into the pars plana, it should be 3.5 to 4 millimeters from the limbus. You should remember if you’re making the 4 millimeter tunnel, then you have to change the direction of your needle at 1.5 millimeters to insert it into the sulcus. So it is 1.5 millimeters. So another question is: What is the laser power needed to remove the blood clotting? It’s a very low power. You can just start with 1 to 1.5 millijoules. And if it doesn’t get cut with that, you can increase it slightly, but it shouldn’t be what you use in YAG PM. It is low power. 1 to 1.5 to 2 millijoules. So again, the same question — what was the power? Low power. 1 to 1.5 millijoules. For disrupting the blood clot. Or iris incarceration. So can antimetabolites be used with valve surgery? I have already answered this question. Latest studies are showing good success with mitomycin C. You can use it as a sponge. At an area where you are going to place your plate. So it can be 0.4 milligrams per milliliter. Or you can use it as an injection at the end of surgery into the bleb. So it reduces the fibroblastic reaction into the bleb. So it can be used. Another question is: What should be the direction of bevel in AC? Yes, so direction of bevel should be up. So if it is in AC, it should be up. And if it is in the sulcus, it should be down. So the logic behind it is that you do not want incarceration of iris into your tube. So if it is in sulcus, it should be bevel down, so it doesn’t incarcerate the iris. In case if it touches the iris, the iris is not pulled. Into the tube. Both for pars plana and sulcus, the bevel should be down. Yeah, I think that’s a very good question. In case there was recurrent tube erosion, why was the sclera reduced to half thickness? Wouldn’t full thickness be better? You can use at full thickness also, but as you could see in the case, there was recurrent tube erosion, and the conjunctiva was falling short. So if you use a very thick graft, your conjunctiva will be deficient. So just in order to make the sulcus plane — because one of the reasons of tube erosion is that the surface is irregular. And it is not flat. So the frequent blinking of the eyelids over the conjunctiva — if the surface is not plane, if it is elevated, it will cause even more erosion. So in that particular case, we decided to make it thin, so that the surface becomes more plane. And the chances of erosion reduces. But if it’s a first time erosion and the conjunctiva is in a very good state, I generally use full thickness scleral patch graft. So I think that’s okay. To use half thickness or full thickness. Prolene suture, as I said, I use 4-0. But it is better to use 3-0. Because 4-0 will not completely occlude the tube lumen. It will just occlude 60%. If it is 3-0, it will occlude almost 95%. 3-0 is better if you want pressure to be reduced. If you want the pressure to become high. Or if you want the lumen to be blocked completely. But if you want partial occlusion, then you can use 4-0. Otherwise, also, intraluminal tube stent is a reversible procedure. If your pressure rises, you can just remove the stent. So that is why it is a reversible procedure and is a kind of less invasive, as compared to the other more invasive procedure. Where you are opening up the conjunctiva and then ligating the tube, removing the scleral patch graft. So preferably, you should use a 3-0 prolene suture. And in other studies, they have used two 5-0 nylon sutures also. So if you don’t have the 3-0 prolene, you can introduce two 5-0 nylon sutures. There are case reports where they have used 5-0 nylon, and it completely occludes the tube. So another question is: How does the free scleral graft survive? Yeah. Free scleral graft is used in some patients. Where in the conjunctiva is in a good state, there is a small erosion, the surrounding conjunctiva is vascularized. Then you can use… The question is free scleral graft. I thought conjunctival graft. I think scleral graft, in any case… You are going to cover the tube with it. And it is just like cover over the tube. So if a patient is not having immunological reaction, it survives in most of the patients. There is no melt which is observed. And for conjunctival graft, again, free graft can be used — the surrounding conjunctiva is in a good state. The surrounding conjunctiva is necrosed, if it is very scarred, then it is better to use the conjunctiva pedicle graft, as I said, which is a vascularized graft. And where in the conjunctiva is free on one side, but it is attached on the other side, from where it draws the blood supply. So for that condition, I think you have to use the pedicle graft. So another question is: How do you decide if Vu to do the AADI or AGV, apart from scarring? That’s a very good question. There’s always a confusion which implant to use. I think indications are not very clear cut. But yes. Some of the indications, if you want the pressure to be reduced immediately, the patient is having multiple comorbidities, the patient is having cataract, corneal scarring, and you’re planning multiple surgeries, you want to reduce the pressure, then you have to go in for another surgery. Like cataract surgery or VR surgery, your obvious choice will be AGV, because you don’t want to delay your next surgery to that extent. Because with AADI, you have to wait for at least two or three months before you can perform another surgery. ’til your pressure normalizes. With AGV, you can perform another surgery within weeks. And also, I would perform AGV in patients who had history of uveitis and who have history of hypotony. Before. Or in patients where the scleral rigidity is very low. And there are chances of postoperative hypotony. So in those cases, I would prefer a valved implant. But if you have enough time, if you want lower postoperative intraocular pressure, and you don’t have to perform the second surgeries soon. I think you can go in for AADI. Again, if your patient can come for follow-up. If your patient can’t come for follow-up, I would say that AADI or any non-valved implant will not be a good choice. So that is how you can decide. So another question is: Is there a risk of 4-0 prolene suture falling out of tube? No. I think — as you had seen in the video, it is introduced quite far. As far as you can introduce it. So it’s not just at the tip of the tube that it can fall. You have introduced quite a length of the suture into the tube, lumen of the tube. So I don’t think it will fall. While you are putting it in the tube, you have to hold the tube properly so as to introduce it properly. And you have to work with both your hands, so that you don’t lose the suture while you’re introducing it into the tube. But once it is into the tube, the chances of it falling out of the tube are lower. Another question is: How to decide whether to put tube in sulcus or AC. I think this is, again, a very good question. As far as possible, if you have a good sulcus, if you can put the tube in sulcus, if the pupil is not very round and regular, in most of those patients, the pupil is dilated, irregular, and there is some distance between the iris and the IOL. PC IOL. So those are the ideal cases for putting the tube into the sulcus. Where you have enough space in the lens and your sulcus is very dilated. But in patients who have a small pupil, the pupil is very small reacting, it’s not a very good idea, even in a pseudophakic eye, to put the tube in the sulcus. If at all, if your AC is very shallow, then you can make an iridectomy, and then put the tube through the iridectomy, and the iridectomy will deepen the chamber at that area. And then you can put the tube to the iridectomy and then bring it over the iris in phakic patients. And if the AC is very deep, if the patient is pseudophakic, there is enough space in the anterior chamber, you can put the tube in the anterior chamber. But I would like to emphasize again here that it is always better to be close to the iris, rather than close to the cornea. It will not cause any harm, even if it is touching the iris. In so many patients we have seen the tube is very close to the iris. It is almost lying over the iris. But it doesn’t cause inflammation or anything. And there is no reaction or inflammation. Sometimes it can cause inflammation if it is in the sulcus and constantly touching the iris. But in the anterior chamber, if it is touching the iris, it doesn’t cause much problem. And if it is touching the cornea, then you will have a lot of problems. It can cause corneal decompensation. I think you have to decide depending on the depth of the anterior chamber, extent of PAS, and the lens status of the patient, if the patient is phakic or pseudophakic. In children, what is preferred, AADI or AGV? In children, in less than one year, I think there’s no preference in children. You can put either of the implants, AADI or AGV. But then if you do AADI, you have to see — even with AGV, you have to look at the position of the tube, and as the child grows, as the child eye enlarges, there are chances in children that the tube may get retracted. So it is important that you leave a little longer tube if you’re performing the implant in children. Because the children have more complications in terms of tube retraction. And even frequent rubbing of the tube can cause tube erosion. So when you’re very careful — otherwise, there is no choice. You can use either AADI or AGV. So another question is: Do these implants have a life? Five to ten years? There is attrition every year. 5% decrease of the implant as far as IOP reduction is concerned. So the implant, which is very successful, the initial years, may lose IOP control over a period of time. So yes. As for any glaucoma surgery, we are not sure how long the surgery was going to last. But as I have seen in my experience, most of the tube implants, if there is no other progressive rigidity, they may last several years. The efficacy may reduce. But you can add eye drops. And the pressure may be controlled with the adjunctive use of eye drops. Another question is: In the last case of 4-0 prolene, occluding tube lumen, can we tie the tube with vicryl in AC, in addition to lumen occlusion? I have never tied the tube in the anterior chamber. Because it may be difficult to tie it. You have to use… You have to bring it on one end and you have to use instruments to tie it. But I have tied the tube by opening up the conjunctiva close to the plate. And you can just put the ligature. I had shown the implant. You can just tie the tube by opening up the conjunctiva close to the plate. So I have not done it for… (audio drop). So I can’t see the questions and answers now. Oh, yes. So in case there is cataract formation with implant surgery, how do you — how long do you wait to do cataract surgery? So tube implant has no relation to cataract surgery. It doesn’t fail if you perform the surgery early in the postoperative period. As the trabeculectomy. Because for trabeculectomy, for the bleb to get mature, you have to wait for three months for the success of trabeculectomy. But in the case of tube implants, you can do it even after a month or so. So I don’t think… The inflammation is also not so much. So do you use general anesthesia? No, I do not use general anesthesia. Most of my patients I do in peribulbar block. Unless the patient is a child. So in your practice, does the survival of graft differ if it is done as solitary procedure or combined procedure with cataract surgery? This is an important question. If you are providing tube implant surgery with penetrating keratoplasty, I think the chances of survival of graft are not as good as if you’re performing it before or after. Because what happens is that when you perform the surgeries together, the tube implant surgery will reduce the intraocular pressure. And that will cause loosening of the sutures of keratoplasty. Because if you put sutures while you’re doing the keratoplasty… So it will cause shallowing of the anterior chamber. Lowering of IOP. And loosening of sutures. So I think that is not a very good scenario. So I would advise that the procedure should be done separately. So not only for keratoplasty, but also the DSAEK, because you want the graft to stick to the cornea. But if the pressure is low, the purpose is not served. So it is always better to do the surgeries separately. Another question is: Frequently I did bleb tap combined with 5FU in managing hypertensive phase with high encapsulated bleb. Do you do that too? Yeah. I have shown that you can just tap the bleb with the 30 gauge needle, and that will just decompress the bleb. But again, there’s a tendency for the fluid to collect again. So you need to do a serial tapping of the bleb. And I have not used 5FU along with that. But I have done sometimes a tapping. Although not very frequently. But that is a procedure which has been advised. Again, I think anterior chamber, the preferred site placement — I think it depends on the clinical situation. In pseudophakic patients, you can place it in the anterior chamber. In phakic patients, you don’t have any option. You have to place it in the anterior chamber, because you can’t place it in the sulcus in phakic patients. You have to place it in the anterior chamber. So in case one month post AADI, the AC became flat and the IOP is markedly high. What would you suggest to do for this patient? So I think this is a different scenario. One month post-AADI, we would expect the suture to get resorbed, to break spontaneously. And the pressure should become low. If the pressure has become markedly high, that’s a very unusual scenario with AADI. Because you expect the sutures to dissolve by one month. In case the sutures are still not dissolved, then you are expecting some complication like malignant glaucoma, where the AC has become flat. And the intraocular pressure has risen. So you have to then do the UBM or B scan to find out the causes, which can be there, and they are pushing the iris lens forward. So you have to find out those causes, if the pressure is high. Because we do not expect that in the case of AADI implant. So how was the conjunctival pedicle graft taken? So I think there’s a procedure which is described by Dr. Davinder Grover. And what you do is that you dissect the conjunctiva deep in the fornix. Which is away from the — away from your site of erosion. And you just elevate the conjunctiva with the xylocaine. And then just start cutting it, dissecting and cutting and undermining it on one side. At 3 or 4:00. And then you just come up to the 12:00. And at 12:00, your conjunctiva is still attached. So that is… So you have just got a graft. Which is free from everywhere except at 12:00, where it is attached. So now it has become like a pedicle. And then you just bring it over the site of erosion. So you have to just get it over the site of erosion. So that flap is still attached at one point from where you can get the vascularization. So that is why it is called pedicle graft. The vascular supply is intact, and it is useful in patients who have eroded or avascular conjunctiva. So the pedicle graft is going to take care of the vascularization. So if you want, I think you can go to YouTube and watch the videos. How it has been performed. Is it better to keep the tube longer on AC versus shorter? If you keep the tube very long, if it is close to cornea, it is going to cause corneal endothelial damage. So if your AC is not so deep, it is always better to keep the tube shorter, so that it doesn’t touch the length of the cornea. But in children, as I said, since the eye will grow over a period of time, you have to keep the tube long. So it depends, again, on the age of the patient. On the diagnosis. Whether the patient is having the associated comorbidities. Otherwise, as described in literature, in a normal, routine case, the length of the tube should be 2 to 3 millimeters inside the anterior chamber. So what is your experience… What material could be used as a tube extender if the tube is touching the endothelium and needs to be repositioned? So there is a tube extender which comes… Which is there. AGV — implant. So you can use the tube extender. So you can just… The diameter of the tube extender is more than your tube. So it can fit into your tube and you can introduce the tube extender into the anterior chamber. You can deposition the tube with the tube extender. So yeah. You can add second AGV in another quadrant if the first one is non-functional. If you have done the first one in superotemporal quadrant, you can do the second one in either superonasal or inferonasal quadrant. But I would suggest here… If you have done first implant as valved implant, AGV implant, if it has failed, it is better to use non-valved implant. And if you use it in inferonasal quadrant, because inferior fornix is shallower, the AGV implant is slightly bigger for the inferonasal quadrant. You can use AADI, and you can even cut the wings if you want to make it smaller. So I would suggest if the first valved implant has failed, it is always better to use a non-valved as a second implant. So is the management of flat AC in AGV the same as management of flat AC in trabeculectomy? Yeah. There is some difference. Because even if you put viscoelastic in the anterior chamber, it is flat AC in AGV. The viscoelastic is not going to be retained for long. It is going to pass through the tube. So you have to see why the AC has become flat. Whether there is excessive flow to the tube. And if it doesn’t respond to conservative measures, you can use Healon GV. Which stays longer in the anterior chamber. But if the conservative management fails, you need to find out the cause. And if there is excessive flow through the tube, then you have to tie the tube sometimes. So how do you angle the 23-gauge needle? That tube is nearer to iris than corneal endothelium. So I make it in a Z shape. I bend it in a Z-shaped manner. For the ease of insertion. So if you’re just directly inserting the 23-gauge needle, you cannot get it parallel to the plane of iris. But if you make it or bend it in the form of Z, then it is easier to insert it into the chamber or sulcus. So I generally prefer to bend it in a Z shape. So what is the future of nano-based glaucoma drainage devices? I think this is the last question. So now we have — I don’t know. Now we have newer GDDs coming up, and now we have Clear Path, which is available. So it is a better design. And it’s very flexible. So I think that is a new thing. And maybe in future we are looking forward to better glaucoma drainage devices. And they are different from the shunts which are used for minimally invasive glaucoma surgeries. Because drainage implants should have a reservoir, wherein the aqueous gets collected. But minimally invasive glaucoma surgeries — you use the tubes, the microshunts, those are just tubes. They do not have any reservoirs. And those tubes are different. So there are no more questions. And thank you very much. And I would like to thank Cybersight for giving me this opportunity. And for interacting with you. I really enjoyed the session. And was really happy to answer all your queries and questions. So thank you very much once again.

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August 19, 2021

Last Updated: September 12, 2022

1 thought on “Lecture: Glaucoma Drainage Devices & Managing Complications”

  1. Thank you soo much Cybersight for made it possible, thank you for permit many ophthalmologists and optometrists learn more about different topic about the eye health. Thank you for create Cybertsight, it help a lot.


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