In this lecture, Dr. Brookes looks at some of the pre-operative and post-operative outcomes associated with a good outcome.
Lecturer: Dr. John Brookes, Moorfields Eye Hospital, London
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DR BROOKES: Thank you very much and good morning, everybody. This morning, I’m going to talk about trabeculectomy surgery. This is the traditional operation that we use to treat glaucoma, which has been used for many years, and it’s developed over many years, and so the technique has improved, and so what I’m gonna do this morning is look at some of the preoperative and postoperative factors associated with a good outcome. So this is the whole range of glaucoma surgery that’s available to us. So in children who have childhood glaucoma, we have angle surgery, which is either goniotomy or trabeculotomy, filtering surgery is the trabeculectomy we’ll talk about, usually with antimetabolites. Later in the week, we’re going to talk about glaucoma drainage implants. And these are usually reserved for people having failed trabeculectomy or certain types of secondary glaucomas. We’ll also talk about cyclodestruction. Cyclodiode laser. Many of my — I specialize in pediatric glaucoma, so many of my slides are of children. But really I’m going to talk about adult trabeculectomy surgery, which is more appropriate for all of you to do. As you can see from this child who had a trabeculectomy, trabeculectomies can give very, very good surgical outcomes. This child has primary congenital glaucoma, and you can see with a trabeculectomy, within a few days, the cornea has started to clear. But there’s also a bad reputation for trabeculectomies, because there are many complications from trabeculectomy surgery, like I’ve illustrated here, and I’m gonna try and explain how we try and avoid many of these complications. So you can see we have a bleb leak, a blebitis, and a bleb-related endophthalmitis. From a patient’s perspective, what is it like to have a trabeculectomy? The problem with glaucoma in general is that, from the patient’s perspective, the patient is asymptomatic. Then you offer them eye drops, which cause them to have red, uncomfortable, itchy eyes, and if medical treatment fails, then you offer them surgery, which has the risk of surgery, in an eye that already sees quite well, from their point of view. And with this sort of surgery, we’re only aiming to maintain vision. So it’s an operation that is not aimed at improving vision. It’s there to stop any deterioration. And the many problems we have trabeculectomies is that the vision may well deteriorate, it may become uncomfortable, you may develop a cataract as a side effect of the operation, and there’s a risk of infection. So an ideal trabeculectomy is one where the patient experiences no change in vision and no discomfort. And an ideal trabeculectomy for the doctor is where we have posterior drainage, where we have a large, diffuse bleb, where there’s no risk of infection. I’m sorry about the quality of this slide, but what we want to go from is where we have elevated, uncomfortable, cystic blebs to one where you can hardly see the bleb, because it’s large and diffuse, with very little risk of infection. The basic idea of a trabeculectomy is that we want to create a fistula, draining aqueous from the anterior chamber to the subconjunctival space, to maintain a low intraocular pressure. We’re gonna talk about some of the complications, but the main complications we want to avoid is, firstly, the scarring response, which allows — which stops the drainage of aqueous, and the major complications of hypotony, infection, and hemorrhage. So let’s just look at some preoperative considerations to start with. The first thing we need to avoid is a rapid reduction of intraocular pressure, because there is a risk of a decompression retinopathy, and a risk of suprachoroidal hemorrhage. So we want to control the intraocular pressure as much as possible before the surgery, even if that means a general anesthetic, because all general anesthetics lower intraocular pressure. We want to provide an optimal environment for the surgery, where there’s no risk of infection, such as lid problems like trichiasis, entropion, and blepharitis, and no conjunctival inflammation. We use povidone-iodine in the inferior fornix, to try and sterilize the operative field, and try and keep the eyelashes away from the surgical site. When we’re considering anesthesia, we need to consider whether a patient would benefit from either a general anesthetic or a local anesthetic. And so the considerations for a general anesthetic may be — if it’s a very high preoperative intraocular pressure, and if there are high risk cases, meaning young patients, meaning high myopes, or patients with only eyes, where there’s a higher risk of complications. We might consider general anesthetic. Most patients have a local anesthetic, and we generally prefer a sub-Tenon’s local anesthetic. So again, you’ll see in the surgery this afternoon — but it’s important to get good exposure of the conjunctiva. So we use a traction suture, usually a 7-0 silk suture, which is a corneal traction suture. I think the conjunctival incision is very important, because what we want to achieve is posterior drainage. And what we nowadays do with the conjunctival incision is generally a fornix-based incision, and this improves the morphology of the bleb. If you make a limbal incision, you then allow a ring of scar tissue to develop, which limits posterior drainage. So if you make the incision — if it’s a limbal-based, so the incision is more posterior, you allow scarring, which then limits posterior drainage. And with these sorts of blebs, they tend to be quite anterior, and they are more prone to becoming cystic, and these are the blebs that are more at risk of bleb infections. Now, we always need to use antiscarring agents during trabeculectomy surgery, because of the risk of scarring. So the treatment area needs to be large, so we get a diffuse, large bleb, and the antiscarring agents, the most common ones, would be 5-fluorouracil, and mitomycin C. Generally, the antiscarring agents can be used either as swabs soaked in the cytotoxic agent, or they can be injected subconjunctivally at the start of the procedure. And nowadays, I generally always use mitomycin C, injected at the start of the operation. And the concentration depends on the risk factors for scarring. So if you have a very high risk of failure, because of risk factors such as young age, conjunctival redness, multiple eye drops, Afro-Caribbean race, for instance, you would always use a high dose of mitomycin. If there’s a very low risk of failure — for instance, very elderly patients — we can use 5 fluorouracil. Moderate risk, mitomycin at a low dose. High risk, mitomycin at a higher dose. And these are just some of the risk factors. Actually, I’ve listed some more of the risk factors here, and you can see previous conjunctival surgery, race, persistent redness/inflammation, neovascularization, early onset — these are all risk factors for scarring. So I’ve just got some pictures going through different stages of the trabeculectomy. So you can see the principles of treatment is to always use plain forceps when you’re touching the conjunctiva, and with a fornix-based incision, it’s very important to dissect posteriorly, so the aqueous drainage is away from the limbus. So the antiscarring agents can be either treated with sponges soaked in the mitomycin or injected. We tend to like a large rectangular scleral flap for the trabeculectomy, because that allows more posterior flow, so there’s no anterior drainage, which increases the risk of infection. A large surface area. And a flap that’s easy to massage, to encourage early drainage. So you can see this is a congenital glaucoma eye. But you can see there’s a very large scleral flap. The other point is that the rate of incisions are not — don’t extend to the limbus. And again, this is to avoid drainage at the limbus, to avoid anterior blebs. It’s important to, before you enter the eye, before you perform the sclerostomy, to perform a paracentesis. This allows you to reduce the IOP gradually, and it also allows refilling of the anterior chamber, if the eye pressure falls dramatically. To make the sclerostomy, we generally use a punch, which allows a sclerostomy over 50 microns, and a Kelly punch is usually about 500 microns. The very main consideration to avoid in any sort of glaucoma surgery is to avoid a rapid reduction in pressure. So in high risk cases, where the consequences are very serious, like aphakic eyes, like children with Sturge-Weber, where there’s a risk of bleeding if the pressure drops too low, we always try and use an anterior chamber infusion, to maintain the anterior chamber. So we always do a peripheral iridectomy as well. It’s peripheral. The only times you might not do a peripheral iridectomy is if there’s a bleeding tendency, or if the eyes are pseudophakic. Because the purpose of an iridectomy is to stop the peripheral iris from blocking the sclerostomy. And if the eye is pseudophakic, the iris is quite posterior. So the risk of blocking the sclerostomy is quite low. So let’s talk about our suturing now. So the sutures are there to prevent uncontrolled hypotony. So we generally use releasable sutures. Now, these sutures can be adjusted and removed after the surgery, if you haven’t achieved a low enough target pressure. And the idea is that when these sutures are tied to hold down the scleral flap, we try to achieve no flow. And what we want to be able to do is, if there’s no flow at the time of surgery, we know, then, there’s gonna be no postoperative hypotony, no shallow anterior chambers, but then we can adjust the pressure to the correct level. We need to make sure that the conjunctiva is meticulously closed, so there’s no leak from the conjunctival edge. And also we tend to prefer a 10-0 nylon suture, because this doesn’t cause any conjunctival inflammation. And then we give a subconjunctival injection of an antibiotic and a steroid. So this is just a little drawing of some of the features that we use to try and achieve a good trabeculectomy. So here you can see we try to avoid — we’re trying to encourage posterior drainage. The scleral flap is not cut to the limbus. And there’s meticulous conjunctival closure. I want to talk about postoperative management. Because I think the postoperative management is equally — or if not more important — than the surgery itself. The reason it’s very important is that you really want to avoid having any scarring. And you need to encourage early drainage. So we use a combination of a steroid, but very frequent steroids — every 1 or 2 hours — and an antibiotic. And the benefit of the releasable sutures is that if the pressure is not at the optimum level, the releasable sutures can be removed as early as one week after the surgery. It’s important that in young patients and in high myopes that we try and leave the releasable sutures a little longer. Because they’re more prone to hypotony. And so I would suggest that, in this type of patient, the releasables aren’t removed for at least 2 or 3 weeks postoperatively. If you see early inflammation or early scar formation, you can give subconjunctival injections of steroid or 5-fluorouracil. And the steroid drops can continue for at least 6 to 8 weeks after the surgery. Postoperatively, we’ve got to always bear in mind how we manage overdrainage. So if we get an overdraining bleb, but there are no complications of low pressure, such as maculopathy, we can treat this conservatively. And that might mean reducing the frequency of the steroids, cycloplegia, or injection of viscoelastic into the anterior chamber. If you have postoperative low pressure with complications of low pressure, like maculopathy, then usually these patients need to be taken back to theater and very sutured. Long-term, how do we get trabeculectomies working again? We’ve got needling procedures to try and free up any scar tissue. We can repeat the trabeculectomy at a different site, and there’s also an option, a trabeculectomy has failed, then the next surgical option is probably a glaucoma drainage device. So that’s a brief overview of the trabeculectomy surgery. But if there’s any questions, please let me know. Well, needling can be done early, if there’s encapsulation. So within the first 4 to 6 weeks. Usually it’s done late, months or years later. If it’s a failing trabeculectomy. So it can be done at any stage after the trabeculectomy. No, we don’t use any cycloplegia or atropine, postoperatively. It used to be done very frequently, but we find we don’t need to do that, nowadays. The only time you may consider it is if you’re operating on a very small eye, because there’s a risk of aqueous misdirection. But as a general rule, for trabeculectomy, we don’t use atropine. How long after the surgery? 6 to 8 months. Then I would probably do a needling procedure, then. Yeah. Because it’s usually… With needling, the idea is that you put a needle into the bleb, because you’ve got to decide whether the scarring is subconjunctival or whether it’s under the scleral flap itself. And so if the scar tissue is subconjunctival, a needling procedure works quite well. If the scarring is underneath the scleral flap, then with the needling procedure, you would need to go into the anterior chamber, with a needle, to free up that scar tissue. But 6 to 8 months is a reasonable time to needle a trabeculectomy, if the pressure is still high. You can still get a trabeculectomy functioning after that length of time. Well, you can either suture two ways. You can do a thick suture, in which case, you would need to do argon laser suture lysis afterwards. Sometimes it’s not always easy to access the laser, so a releasable suture tends to be a little bit easier. But the idea is that you leave a loop of the suture within the cornea. And in that, you’re able to just grab the end of that with a needle, and then forceps, just to pull it out. So the releasable suture is tied in four throws, because that’s a stable knot. But when you pull the end of it, it releases. It’s like untying a shoe lace. You’re able to see the end of the suture within the cornea. And so it’s much easier in the clinic to remove a releasable suture than it is to have to go and find a laser and do suture lysis. How long before you remove it? Well, the releasable sutures — if the pressure is at the optimum level, the releasable sutures will stay there permanently. The earliest time you would consider removing a releasable suture is one week postoperatively. But if there are risk factors for overdrainage, like I mentioned — the young high myopes — at least two weeks. But you have to remove releasable sutures within six weeks, postoperatively, because if they’re left longer than six to eight weeks, it’s very difficult to remove them, because they get scarred, and when you try to remove the end of them, they break. So they have to be removed in six to eight weeks, if they’re going to be removed. But you don’t have to remove them, if you already obtained an ideal pressure. Combined surgery is possible. If you look at the results in studies of combining surgery — so a phaco and a trabeculectomy — the results of the trabeculectomy are less than if you separate the procedures. So you get a better outcome from pressure control if you perform the trabeculectomy separate to the cataract extraction. But in certain circumstances, it is worthwhile combining the procedures. So a combined procedure has a worse outcome for pressure control than if you separate the procedures. But there are certain circumstances where, for patient reasons, that you can combine the two. But the long-term outcome for the trabeculectomy is worse. The reason for this is that if you’re combining the procedure, postoperatively, there’s more inflammation, and then that allows the scarring to build up and the trabeculectomy to fail.
June 6, 2017