FEATURE EWAP DECEMBER 2023 23 as the importance of creating a separate paracentesis incision about 3–4 clock hours away from the area of planned stent insertion to allow the Hydrus to optimally match the curvature of the canal. Bleeding (hyphema) is also a possibility with stenting procedures, as is damage that can occur due to contact with the iris root and/or ciliary body. There are two distinct bleeding patterns that surgeons need to be aware of with MIGS. One is a slow, focal, and normal amount of blood reflux. “A little blood reflux is a confirmatory sign that you’re in the right place, doing the right thing,” Dr. Shah said. This is in contrast to traumatic hyphema, which can occur due to inadequate visualization, abnormal anatomy, or patient movement that causes you to inadvertently touch or interact with the iris root or ciliary body. Dr. Shah said that this bleeding is more diffuse and at a higher velocity. He said cohesive viscoelastic should be used to tamponade this type of bleed, preventing more blood from entering the anterior chamber. The surgeon should also take the time to figure out what caused such hyphema and address it, if possible. “Typically, you’re going to have to move half a millimeter to a millimeter more anterior,” he said. Dr. Sheybani said if a stent is placed in the wrong tissue plane, it doesn’t generally cause major intraoperative complications, again, unless it creates a cyclodialysis cleft. He clarified that something like the iStent is so small that even if it were accidentally placed in the suprachoroidal space, it probably isn’t going to cause an issue or significant bleeding. However, if the patient moves, the instrument doing the stent injection could create this damage. Dr. Sheybani also said that a misplaced stent could cause chronic iritis if it’s rubbing against structures it shouldn’t. In the event of physical tearing or disinsertion of the iris or ciliary body, Dr. Shah’s recommendation is to leave alone a small iridodialysis. If it’s big, it may require repair, which Dr. Shah said is a specialized skillset. Cyclodialysis cleft comes with a risk of postop hypotony. If it’s small, Dr. Shah said that a little postop inflammation can help seal it up and it will scar closed. Overall, though, if there is a cyclodialysis cleft, surgeons should monitor for postop hypotony, indicating a need for repair of the cleft. Dr. Sheybani said small clefts should close on their own once the patient is off steroids. Complications with the ‘otomies’ and ‘asties’ Dr. Shah said that hyphema and iridodialysis or cyclodialysis can also occur with goniotomy, trabeculotomy, and canaloplasty. With canaloplasty, Descemet’s detachment can occur. “It typically happens if we over inject viscoelastic in one focal area of the canal. That can cause the viscoelastic to track anteriorly, pulling Descemet’s off,” he said. “You’ll see lenticular mass in your field of view, which would be Descemet’s bowing down into the anterior chamber and the viscoelastic-filled space starting to occlude the anterior chamber.” Dr. Shah said recognition of this situation early is key because it can then be easily managed. He said to cut down through the anterior cornea into that space, evacuating viscoelastic from an anterior approach and consider placing an air bubble to reapproximate Descemet’s. Complications with blebforming MIGS Though a bleb-forming procedure, XEN (Allergan) lives within the MIGS family, Dr. Shah said. Complications that can occur with XEN include malpositioning or unstable positioning, which Dr. Shah said is rare, and bleb-related issues. Dr. Shah said there are a number of ways to place XEN (ab externo and ab interno), but the key is to make sure you have the right amount of the device in the anterior chamber and the subconjunctival space, and ensure that the “subconjunctival” portion is not enmeshed in Tenon’s. In terms of bleb-related complications, these can include fibrosis, scarring, encapsulation, infection, and device exposure. These, Dr. Shah said, are less common with good surgical technique, appropriate use of anti-inflammatory agents, and careful management of the wound healing. Dr. Sheybani said when you’re performing XEN with patients with very high pressures, the patient could be at risk for a suprachoroidal hemorrhage. Other possible XEN complications he mentioned were bleeding if you go through the iris root, conjunctival perforation from the insertion needle pushing through the conjunctiva, and Descemet’s detachment. “Despite these things, in general, XEN intraoperatively is a very safe procedure. I tell patients they’re going to hear me talking about positioning and repositioning during the procedure because I want it perfect before we leave,” Dr. Sheybani said. “Repositioning at the time of surgery is not a worrisome thing for me because the intraop complications are so unlikely. … There is hypotony that can occur within the first 1–2 weeks, and there can be choroidals. There can be hyphema, less likely but possible. The advantage of XEN continued on page 27
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