Eyeworld

70 | EYEWORLD | DECEMBER 2023 G UCOMA have patients with a functioning trabeculectomy who need cataract surgery, I wait at least 6 months until the trabeculectomy is more mature." Dr. Boese added that there is a high risk of failure within those first 6 months. "Beyond that, I don't think it matters much if the trabeculectomy is 6 months old or 25 years old—in all cases of a bleb, you still have a risk of trabeculectomy failure with cataract surgery." While cataract surgery alone may lower IOP to some extent, Dr. Boland said the impact on trabeculectomy is less clear in this setting. He thinks this factor is less important in these cases. If you have a functioning trabeculectomy, most of the aqueous is going out that way, and the native drainage system may not be function- al. He wouldn't expect the pressure to improve just because you're adding cataract surgery. Dr. Boese also said to be cautious when con- sidering studies that show that cataract surgery alone can reduce the IOP. "This is not the case in glaucomatous eyes with a trabeculectomy," she said. "Studies have shown that even with careful monitoring, IOP on average climbs 2–4 mm Hg following a cataract surgery in an eye with a functioning bleb and sometimes much more than this." This is thought to be because the small amount of intraocular inflammation stirred up with surgery is enough to scar down the bleb. It can be managed with close post- operative follow-up and steroids. "In cataract surgery following a trabeculectomy, I will often have patients start prednisolone dosing at every 2 hours while awake, rather than my typical QID dosing," she said. Dr. Boese noted two preoperative factors that help her prepare for trabeculectomy failure after cataract surgery. "One is where the IOP is compared to our target, and the other is the bleb morphology," she said. "If the IOP is much lower than our target, we have enough buffer to accept a small reduction in bleb function. However, if we are just at target or if the patient is requiring additional use of glaucoma drops, I am more worried that it will fail. With regard to the bleb morphology, I worry much more about very shallow or flat blebs than taller, diffuse blebs with robust conjunctiva." There are also intraoperative risks. A short and uncomplicated cataract surgery will have a much lower risk than a long and complicated the trabeculectomy to not work as well or to fail entirely," she said. "There are things that can be done to minimize this, but it can still happen even when all precautions are taken." Another important preoperative consider- ation has to do with IOL calculations. If the IOP is on the low side from a well-functioning bleb, Dr. Boese said two things may cause the IOL calculations to be off. One is that a softer eye is often a bit shorter. "If the IOP increases follow- ing the surgery and the axial length increased, you may have a myopic surprise, sometimes by a significant amount," she said. The other aspect that can be off is the astigmatism. "A soft eye will often have regular with-the-rule astigma- tism, something that resolves when the IOP is increased," she said. "I am especially careful not to place a toric lens in these patients if I suspect that the trabeculectomy may be responsible for part of the astigmatism I'm seeing." Dr. Boland said he won't perform cataract surgery until the patient has visually significant symptoms because of the increased risk for trabeculectomy failure. He noted that there's some evidence that the earlier you do cataract surgery, the more likely you are to cause failure of the trabeculectomy. There's a concept of the trabeculectomy getting established over months to years, and the longer you can wait, the less likely it is to fail. Dr. Boese agreed that you should wait to do cataract surgery until there's a visual impact. "If the cataract is not bothering the patient, I won't remove it because every extra year that we can get from a well-functioning bleb is a win," she said. "However, every patient reaches a point where they are ready, and there isn't any use delaying. I'd much prefer a straightforward and uncomplicated surgery to waiting so long that I'm dealing with a brunescent lens." Dr. Boese said ideally cataract surgery would be performed prior to a trabeculectomy; the second best option is to do a combined phacoemulsification/trabeculectomy. "Whenever a patient has a cataract that I anticipate will be visually significant within the next couple of years, I'm typically planning to do a combined phacoemulsification/trabeculectomy so I don't have to worry about running the risk of doing the phacoemulsification later," she said. "Of course, this is not always possible. When you continued from page 69

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