Eyeworld

80 | EYEWORLD | FALL 2024 G UCOMA References 1. El Helwe H, et al. Comparing outcomes of 45 Xen implan- tation ab interno with closed conjunctiva to ab externo with open conjunctiva approaches. J Glaucoma. 2024;33:116–125. 2. Tan NE, et al. Comparison of safety and efficacy between ab interno and ab externo approaches to Xen Gel Stent placement. Clin Ophthalmol. 2021;15:299–305. 3. Yuan L, et al. Short-term outcomes of Xen-45 Gel Stent ab interno versus ab externo transconjunctival approaches. J Glaucoma. 2023;32:e71–79. 4. Ruda RC, et al. Clinical out- comes of ab interno placement versus ab externo placement of XEN45 Gel Stents. Ophthalmol Glaucoma. 2023;6:4–10. Relevant disclosures Li: MicroSurgical Technology, New World Medical, Nova Eye Medical Yohannan: AbbVie, Alcon Contact Li: lia2@ccf.org Yohannan: jyohann1@jhmi.edu Dr. Li said there are still scenarios where she thinks ab interno is warranted. These in- clude when she is trying to conserve conjunctiva or if she's worried about postop healing. Obstacle #2: Needling While the needling rate is lower with the ab ex- terno approach, according to Dr. Li and Dr. Yo- hannan (in some cases, it's difficult to even see the stent to perform needling with the sub-Ten- on's placement), lessons have been learned over the years regarding needling with the XEN. "Initially we thought 30% of patients after the XEN needed an in-office needling, and that was a big hurdle in terms of the success and maintenance," Dr. Li said. "More people are gravitating toward primary needling at the time of surgery prophylactically to push back the Tenon's and prevent them from coming near the XEN. That has decreased the postoperative needling rate." Obstacle #3: Where to insert Dr. Li said there is a learning curve in deciding where to insert the XEN and how to ensure it gets into the right place. "We were initial- ly thinking it had to be subconjunctival but supra-Tenon's, and now we're realizing that as long as it's not intra-Tenon's, it's OK. It could be sub-Tenon's. There are various ways you can ensure that the XEN stent is in the right space. You can use an air bubble, balanced salt solu- tion, viscoelastic, or even mitomycin-C to create a potential space for XEN insertion when doing it ab internally," Dr. Li said. When placing sub-Tenon's, Dr. Yohannan said it's important to be liberal with mitomycin- C and to ensure you don't kink the stent when you're closing Tenon's. Obstacle #4: Mitomycin-C Since XEN's commercial launch, Dr. Li said how the use of mitomycin-C fits into the procedure— and at what concentration—has evolved as well. "There is still debate on that, but I think based on the patient profile, based on their surface tolerance, their Tenon's tissue thickness, we can do a little bit more or less. There is more personalization as to how much mitomycin-C to give, and we also learned how it can affect the ocular surface under different concentrations and how to manage that postop," she said. Obstacle #5: Low-teens target Dr. Li said that while she can't count on a consistent, low-teens target with the XEN, she has had more success if she modifies the stent, cutting it to be a little shorter than its original 6 mm. "By decreasing the length of the tube, it decreases resistance and increases the flow rate to achieve a lower IOP," she said. "The sub-Ten- on's portion is also a little shorter so potentially you'll have less length to be embedded into Tenon's." Obstacle #6: XEN failure Dr. Yohannan said a lot of avoiding XEN failure comes down to good intraoperative technique. If you're placing it sub-Tenon's, there's not much you can do if it starts failing postop because it's hard to needle in that position, and it's a flimsy stent. "It's going to be hard to separate that thick tissue from the stent, whereas when you're sub- conjunctival, it's a little easier because there's not thick tissue over it," he said. "I think the main thing is ensuring you control inflamma- tion. I'll do steroids every 2 hours for a week. … If you have an occlusion of the proximal lumen from the iris, sometimes doing a YAG to the tip may be helpful. Even if there is no occlusion from the iris and the IOPs begin to go up, a YAG to the tip in the AC to shorten the overall length of the XEN may be helpful to increase flow and reduce IOP. In my experience, needling does not work well when the stent fails after the sub-Tenon's approach. Most of the time, it works well with a great bleb morphology in the right patient, and you're not subjecting them to in-office needlings." If the XEN fails despite these efforts, Dr. Yohannan said he'll add back medications and see how the patient does. If they remain un- controlled, he'll do a trab next to the XEN. "By scarring the XEN, they've shown me that they're able to fibrose well. They're probably not going to become hypotonous after trab," he said. Overall, Dr. Li said, since its inception, many pearls have been learned to overcome some of the initial hurdles with the XEN. "There are so many different ways of doing the XEN, which is exciting," she said. continued from page 79

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