Eyeworld

FALL 2024 | EYEWORLD | 79 G STRIKE! by Liz Hillman Editorial Co-Director About the physicians Ang Li, MD Assistant Professor of Ophthalmology Case Western Research School of Medicine Cleveland Clinic Cole Eye Institute Cleveland, Ohio Jithin Yohannan, MD Boone-Pickens Assistant Professor of Ophthalmology Johns Hopkins University School of Medicine Wilmer Eye Institute Baltimore, Maryland Knocking down XEN obstacles N eedling and hypotony were once more common obstacles with the XEN Gel Stent (AbbVie), however, after several years and lessons learned, many surgeons have adopted new ap- proaches that have increased success rates and reduced the need for subsequent procedures. EyeWorld spoke with Ang Li, MD, and Jithin Yohannan, MD, to get their insights on the pearls they have gained using the stent, which originally received FDA approval in 2016. Dr. Li said she began using the XEN early in practice, shortly after its approval. Over the years, she's found the ideal candidate to be the elderly, Caucasian patient who may be intoler- ant of drops with moderate to severe glaucoma or patients in whom she is looking to avoid tube shunts or trabeculectomy. "It's less invasive and postoperatively more tolerated by most patients compared to tubes or trabs. I do like to use it for surgically naïve patients because it has specific requirements for conjunctiva and Tenon's tissue, so operated-on eyes generally don't do as well, and they scar down more easily," she said, noting that she is usually aiming to get pressures in the mid-teens with the XEN. Dr. Yohannan has similar criteria for XEN patient selection. He uses this stent on patients with uncontrolled glaucoma with more ad- vanced damage whose IOPs are above target. He reserves the XEN for patients at higher risk for hypotony with a trab and those who are at less risk for bleb fibrosis. This includes older patients, high myopes, and patients who are not of African decent. Obstacle #1: Ab interno approach The XEN is approved for insertion in the sub- conjunctival space via an ab interno approach. However, Dr. Li and Dr. Yohannan—and many other glaucoma specialists—have adopted an ab externo approach for certain patients. "If you look at a random survey of glaucoma col- leagues, it's about 50/50 or even more ab exter- no for how physicians are using it," Dr. Li said. The ab externo approach's safety and efficacy has been compared to the on-label, ab interno approach many times. In these studies the ab externo procedure was found to have at least the same efficacy and safety as the ab in- terno procedure—in some cases even resulting in a higher success rate. 1–4 Some of the challenges of the ab interno approach are avoided when doing ab externo, Dr. Yohannan said. These include the skill re- quired for working in the angle with a mirrored gonioprism and finding the right plane for the stent to be placed in the subconjunctival space; a higher rate of needling or the need for primary needling; a higher rate of hypotony in the postop period; and an anterior subconjunc- tival bleb that may be very thin and avascular and prone to leakage, XEN exposure, or bleb dysesthesia. Dr. Yohannan said he converted to open conjunctiva, ab externo for the XEN 2–3 years ago, placing the stent sub-Tenon's. "I dissect into the sub-Tenon's space. I apply high-dose mitomycin-C posteriorly in the sub-Tenon's space (two sponges soaked with 0.4 mg/cc of mitomycin-C placed in the sub-Tenon's space for 2 minutes and another 0.2 ml of the same concentration injected on the sponges)," he said. "I enter the anterior chamber with a 30-gauge needle. … Then I insert the stent through that 30-gauge path. There is very little flow around the stent. It's all coming through the lumen in most cases, which I think pro- motes the formation of that posterior bleb. I'll then pull Tenon's forward, close it, and pull the conjunctiva forward and close it. The blebs that I get look much better, and the needling rate is much lower than with the ab interno approach." While the operative time is more for the ab externo approach, Dr. Yohannan said over the postop course, it's better for the surgeon's time and the patient experience than ab interno. He said it avoids the hypotony and blurry vision. "You don't have this anterior bleb as well, which can be more irritating to patients," Dr. Yohannan said. "I find most patients tolerate the ab externo approach well. The surgery is more involved, but over the course of the patient's lifetime, I would say it's less involved. This is why I made the switch." continued on page 80

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