Lecture: Trabeculectomy

This presentation is about the following:

  1. What are the surgical challenges?
  2. How to avoid complications?

Lecturer: Dr. Christopher Leung, The Chinese University of Hong Kong


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

DR LEUNG: So before I start anything, I just want you to understand — whatever you do to your patients, after trabeculectomy, the only thing that you can ensure the success of the surgery is that, in addition to having a good surgery, is that you need to have a very good and very frequent follow-up — particularly during the first two months after surgery. Now, what happens after glaucoma surgery is that, obviously… Okay. Is it better now? Okay, perfect. So what could happen after trabeculectomy? Now, besides the complications we’re all aware of, including infection, bleeding — these are general complications that can occur after all kinds of intraocular surgery. But I’m talking about what could specifically happen following trabeculectomy. In the initial follow-up, the initial one to two weeks, the most common thing — most common complication that can happen — is hypotony. And then, after a few weeks, the intraocular pressure can go up again. Now, the question I have for you is: Which complication is more difficult to manage? Intraocular pressure too high or too low, following trabeculectomy? How many of you would say high intraocular pressure is more difficult to manage than low intraocular pressure, after trabeculectomy? Hands up. Okay. How many of you think low pressure following surgery is more difficult to manage than high pressure? Okay. Most of you would think — you’re correct. Low pressure is very difficult to manage. Basically you can’t do much. Unless you go back to the surgical room. So you have to ensure, during the surgery, you try your very best to prevent hypotony. What happens if the patient has hypotony? Is that he or she may develop very poor vision. It’s related to the development of macular folds, corneal folds, and the patient will not be happy. So I think the key, which I am going to talk to you, would be how to prevent hypotony. And then, as I said at the very beginning, you need to have frequent follow-up. Because for the first two weeks, you worry about hypotony. After the first two weeks, you worry about the IOP would be getting higher and higher, because of wound healing. And if you see intraocular pressure goes up during the postop period, you have to do something to prevent the intraocular pressure going up. To prevent subconjunctival scarring. And the healing process generally takes about two to three months. So usually what I would do to prevent postoperative subconjunctival fibrosis is to apply frequent steroid. And postoperative topical steroid is extremely important. For the first week, I would generally prescribe 4 times a day. After the first week, I would step up the steroid to 1 to 2, hourly, per day. You can see this is a pretty high frequency of steroid. This high frequency of steroid usually we’d put the patient on for about a month or two. Every 1 to 2 hours. Every 1 hour or every 2 hours. One drop. Yes. Yes. You see, this is critical to prevent scarring. I’ll explain. So… And then after 1 to 2 months, depending on the bleb morphology, I would then step down the steroid again. And you want to step down the steroid slowly. If the patient has been on it every 2 hours, then you may ask the patient to take only the drop every 3 hours, and then every 4 hours, and you tail off the steroid in about another month or two months. So, in total, the patients would probably need steroid for about 3 to 4 months. And one important thing I want to, again, emphasize here is that we do see steroid-induced glaucoma in this region. So please, please remind your patient, when you give steroid to a patient, either after cataract surgery or after trabeculectomy, always remind your patient not to take steroid unless he’s told by a doctor. Because steroid is very good in decreasing the red eyes, reducing itchiness, so it’s a very, very good drug for treatment of various conditions. And the patient may think — wow! This is a wonderful drug. So whenever they have a problem in the future, they would just go to the pharmacy or go to any shops and then get a bottle of steroid and then put the steroid on their own. And that’s when complications happen. So be careful. When you give steroid, ensure the patient only takes steroid according to your instructions. Now I’ll talk about when we perform surgery, when we perform trabeculectomy, what are the key elements that you need to remember. We need to understand all of these surgical challenges during the procedure, and how to avoid complications. As I said, and you all agree, overfiltration is more difficult to manage than underfiltration. And these are the complications I just mentioned. So these are the side effects. These are the complications that can happen if the IOP is too low. And they are difficult to manage. So we need to do our best to avoid the intraocular pressure going too low after the trabeculectomy. And I believe you need to have a very careful dissection and closure of the scleral flap. Now, I understand there are different techniques different surgeons would like to use to create their conjunctival wound or their scleral flap. As I mentioned on Tuesday, we don’t have data in the literature suggesting a particular size of a scleral flap would be more useful or having a more successful outcome following the surgery. But my personal practice here is that I need to have a very sharp-edged scleral flap. And after the surgery, as I said, after the first two weeks, then you will be getting worried about the intraocular pressure going high again, because of tissue fibrosis. And you can imagine the anatomy of the eye. There are three areas that the outflow of the aqueous can be blocked, after trabeculectomy. So the aqueous — the first passage that it will pass through is the sclerotomy. Sclerotomy is the window that we created after elevating the scleral flap. Sclerotomy is the window, is the channel, that we create after we fashion the scleral flap. So this is the first site that the aqueous can be blocked. And then the second site would obviously be around the scleral flap. But the most important site that fibrosis happens is actually not over here, not over here, but over the subconjunctival space. Why this site is prone to blockage? It’s because this site, subconjunctival space, has a lot of blood vessels. It’s a highly vascularized environment. It’s a highly vascularized environment. A lot of blood vessels. And that’s why fibrosis comes in. Because this space has got lots of blood vessels. So steroid would be very effective to dampen the inflammation and dampen the fibrosis in this area. And then I would just show you the steps that I usually adopt for trabeculectomy. So I use a corneal fixation suture, a 6-0 vicryl. So I was asked the other day could we use bridle suture, retinal fixation sutures? Yes, we can. But the corneal suture would be easier for us to manipulate the eyeball. So, again, we worry more about subconjunctival fibrosis than worrying about steroid-induced IOP elevation. And the reason why patients subsequently have high intraocular pressure after trabeculectomy is not because of steroid-induced glaucoma. It’s because of subconjunctival fibrosis. All right. So let’s go back to the surgical steps. I just mentioned we — I tend to perform a fornix-based trabeculectomy. Again, the terms can be confusing. Fornix-based means the base is at the fornix. And the incision is at the limbus. So this is in contrast to limbal-based, which you have the base at the limbus and you’re incising around the fornix area. It’s not actually the fornix. It’s actually about 1 centimeter away from the limbus that you cut your conjunctiva. So this is a fornix-based limbal incision. Now, the second tip that I would like to share with you about trabeculectomy is that we want to have a sharp edge for the conjunctival flap. And the way I do it is basically — you can see I use a diamond knife to first create a horizontal incision. As you can see, my scleral flap is rectangular in size. And then I use a crescent knife to create the scleral flap. I like the diamond knife because it gives you a very sharp edge of the wound. And now you can see I’m applying mitomycin C, as I said the other day. The concentration I use — 0.4 milligram per mil. For 3 minutes. And the key here is to apply the MMC beneath the subconjunctival space. And now you see I’m creating two vertical incisions to generate the scleral flap. Now, notice that I created the scleral flap here — is a rectangular flap, the size of about 4×4 millimeters. You can do it 3×3, 5×5. I don’t think it matters. And there’s no evidence suggesting that one size is better than the other. And then, after creating the scleral flap, which you can see — the depth which I aim at is about 2/3 of the sclera. The challenge here is: We don’t know the depth — we don’t know the thickness of the sclera, most of the time. So it’s more or less an experience-based kind of dissection. Experience-based kind of incision. Because it’s really hard for you to judge, especially when you’re using a crescent knife, cutting beneath the sclera. It’s very hard for you to know how much I’m cutting at. So… But the key here is you don’t want the scleral flap to be too thin. If you have a very thin scleral flap, then it would be very difficult for you to have a secure closure. You can aim for a little bit thicker scleral flap. I don’t think, again, it makes a difference between 2/3 or 3/4 of scleral thickness depth for your scleral flap. But there are diamond knives that also have a gauge that you can adjust the depth of the knife. So you get a more precise idea of how much sclera you’re going into. Notice that here I am creating a paracentesis. I’m going to inject the Healon. I like to use Healon to maintain the anterior chamber so that we would not have a sudden drop in eye pressure after I penetrate into the AC. Some surgeons use an AC maintainer. This is okay. AC maintainer. You just saw the AC maintainer in the previous case. So basically the reason why I prefer viscoelastic or Healon than an AC maintainer: Because I would usually leave the Healon in the anterior chamber. And to me, I think Healon is a great guardian of the AC, after the surgery. That’s why I use a viscoelastic. And Healon is my choice. I don’t use Healon 5, Healon GV. Healon basically stays in the AC for a couple of days. Two to three days, generally. And then it would be absorbed. So you see now I’m penetrating the AC with a diamond knife. Getting some Healon in before I enter into the AC. So, again, I use a diamond knife to create a little window, and see that the Healon is coming out, and use the Kelly punch to create the sclerotomy. And iridectomy. With a bent scissor. So after creating the scleral flap, after having the sclerotomy — excuse me — after preparing the sclerotomy, after cutting the iris, creating an iridectomy, then I would close the flap with 10-0 nylon. So you can see I’m using a 10-0 nylon, and I would use two sutures to secure the flap. And again, the Healon is in, so that the AC is well maintained. And one can see here is — because we have Healon inside the AC — we don’t see the aqueous coming out. And it’s important to keep the pressure stable. The reason why we see choroidal hemorrhage is because we have sudden drop in pressure. It can happen during cataract surgery. It can happen during trabeculectomy. And perhaps trabeculectomy is a more dangerous procedure than cataract surgery. Because most of these eyes have high intraocular pressure before the surgery. And the sudden drop in eye pressure is a very important risk factor for choroidal hemorrhage. And this is a devastating complication that is very difficult to manage. So the key is prevention. And Healon is very good for that purpose. And then you can see I adjust the tension with an objective of restoring the anatomy. Restoring the anatomy of the scleral flap back to its original locations. So, again, when we stitch the scleral flap, look carefully. I often take some time to make sure that these three edges are well opposed to one another. And then you can close the conjunctiva. And again, I use two 10-0 nylon sutures to secure the conj to the cornea. Now, some of you asked: Can we perform adjustable suture? Yes, we can perform adjustable suture. The reason why I don’t normally do adjustable suture is because we can often perform suture lysis with argon laser, if there is a high intraocular pressure related to underfiltration after the surgery. And tying the scleral flap with two 10-0 nylon, with good opposition of the scleral flap edges, basically, are often sufficient to give you a very stable flow. And then… I used two nylon, 10-0 nylon, to secure the conjunctiva. Generally it’s pretty secure. But you might see in some patients — there might be some leakage after the operation. But these are not very common. Particularly when the wound is actually very small. This is about 4 to 5 millimeters in size. So try to minimize this incision. And it’s very unusual that you see this leakage from this wound, actually. Now, after the operation, in the first week, I mentioned you put steroid four times a day. And then every two hours, every one hour, for another month. So the lady sitting here asked why we apply four times a day in the first week and then more frequent steroid the week after. Good. You’re on time. Because I’m going to answer your question. The reason is: For trabeculectomy, we have two wounds. One external, one internal. So you want to have the external wound heal up as early as possible. And a relatively low dose steroid in the first week would help the external wound to heal up quicker. If you apply steroid very early, right after the operation, if the wound here is big, then it would heal up — not very well. And then you may have leakage. But after the first week, when these wounds heal up, not fully, but mostly, and then you would need to make sure the internal wound is not healing. So it’s actually a very delicate balance. It’s actually a dilemma. A paradox. A dilemma. A dilemma. It’s a paradox. It’s a contradiction. So the dilemma here is we want one wound to be healed and one wound not to be healed. So that’s why we use relatively low dose steroid in the first week, and then high dose steroid the week after. Antibiotics, generally, 2 to 3 weeks, to avoid infection. But generally antibiotics are not the medication that I would worry about. I would worry about the patient not taking steroid regularly. Because it’s pretty high frequency, and the patient may not be compliant. And this is the reason why you need the patients to come back very often, after the surgery. Please don’t ask your patient to come back for follow-up a month after surgery. Because there are many things that you can do to help the patient during the first month. If the bleb appears red, appears hyperemic, then you need to step up the steroid. If the intraocular pressure is going up, then you might also need to consider to perform a laser suture lysis. Or loosen the suture, if you’re doing a releasable suture during the operation. So stepping up, stepping the steroid, is important. So… This is the bleb for the same patient. Postop week one, you can see the bleb is really well-forming. But you can still see the vessels going over the bleb. So this is an indication that you would need to step up the steroid. So I would like to end with this slide. The key for trabeculectomy is to avoid hypotony. And leaving Healon inside the anterior chamber is a very good technique to avoid hypotony. It’s always easier to manage high intraocular pressure right after the surgery than managing hypotony right after the surgery. So if you are injecting too much Healon the inside the anterior chamber during the operation, on the first follow-up, on the first day of postop, you see an IOP of 25, what would you do? You can gently put a gentle pressure beneath the globe, push the globe a little bit up, so that you can squeeze the Healon out, and you can see the Healon nicely coming out and forming the bleb. This is what you would do if the first day postop the IOP is high. And after the first day, the second day, the third day, when the Healon is absorbed, you won’t see high IOP anymore. And then, after the first two weeks, the goal would be to prevent subconjunctival fibrosis. And there are a number of key steps during the surgery that would prevent subsequent excessive fibrosis. The key steps that I listed here include extensive blunt dissection underneath the conjunctiva. So that you would get a very diffuse filtering bleb. Antimetabolite is critical. MMC has been shown to be more effective than 5FU. A higher concentration of MMC has been shown to be more effective than a lower concentration of MMC. So 0.4 milligrams per mil is more effective than 0.2 milligrams per mil. So the approach — I use 0.4 milligrams per mil for 3 minutes. You can modify the approach according to your needs, according to the patient’s conditions. This concentration of MMC generally is very safe. And then you would consider early suture lysis. If the bleb is not well forming in the early postoperative period. Laser suture lysis generally is more effective when we do it early. Than after 2 to 3 weeks after the surgery. If you do not see a bleb in the first 2 weeks, that means perhaps your sutures closing the scleral flap are too tight. Then consider performing argon suture lysis early. I generally would not do it in the first 3 days. And the general recommendation is that you should consider argon suture lysis after a week. After a week of surgery. So this is some reference for your consideration. The final question that I would like to answer about… Is… You were asking why we perform a fornix-based approach, instead of a limbal-based approach. The reason is, when you cut the conjunctiva away from the limbus, that wound tends to form a scar. And that scar would form a barrier, impeding a diffuse filtering bleb formation. And it’s been a general consensus that the fornix-based approach would be more effective than a limbal-based approach, because of this scarring reason. All right. Very good. So I hope you all get what I wanted to tell you this afternoon. And do we have any questions from the audience? About the lecture in the morning? About OCT? Diagnosis of glaucoma? Or about trabeculectomy? Please. I’m sure you have viscoelastic. Some form of viscoelastic. You have viscoelastic when you perform cataract surgery, right? So any form of viscoelastic would do. But I generally will use Healon, because it’s less viscous compared to the other forms. Sorry. Say that again? So the question is: How long would you see a filtering bleb? Is that the question? How long will it take to form a filtering bleb? Is that the question? So when the conjunctival wound is completely healed? And? Oh. Dr. Ting is very knowledgeable, because he reads a lot, and he shares with us the Moorfields bleb classification system. Now, practically, in the clinic, we do not use this system have often. It is a system that we use mostly for research studies. The classification is mainly for classifying what kind of bleb would be more likely to fail. It’s related to the size of the bleb and also the degree of hyperemia. I do not care too much about the classification when I am managing glaucoma patients after the surgery. Say, for example, if we do see the conjunctival wound, it doesn’t heal up well, what I would do is I would step down the steroid. Sometimes I would even stop the steroid for a few days, for the wound to heal up. Because steroid is a big enemy for wound healing. And when you see the bleb is forming, but it looks red, then I would step up the steroid. Because what we’ve learned from the Moorfields bleb classification system is that if you’ve got a very red bleb, that bleb is going to fail very soon. So stepping up steroid would be tremendously useful for that reason. So that’s why you need frequent follow-up. So many things can happen within the first month. So many things can happen within the first month. All right. Very good. So I think you all will enjoy the lecture, and I… Oh, okay.

June 1, 2017

Last Updated: October 31, 2022

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