Eyeworld

EW FEATURE 56 MIGS roundup • July 2017 designed to restrict aqueous outflow and limit hypotony, which is among the more frequent complications we encounter with trabs and tubes," she said. "The XEN may be particularly helpful in patients with cataract and glaucoma who require a combined procedure, with potentially lower risks than those associated with combining cataract with either a trab or a tube." Dr. Vinod finds the XEN to be a reasonable primary procedure in many of the patients who are candi- dates for traditional incisional sur- gery, and she added that the absence of a conjunctival flap and superona- sal placement would not preclude future incisional surgery if needed. "Like trabeculectomy, the XEN Gel Stent may require more in-office postoperative interventions, such as needling and antifibrotic injections, than a tube shunt and would there- fore not be my procedure of choice in patients who cannot come in for frequent follow-up," Dr. Vinod said. When asked about using an ad- junctive antifibrotic agent with each of these procedures, Dr. Vinod said that antifibrotic agents are routinely required with trabeculectomy and the XEN Gel Stent, but she does not use antifibrotics with tube shunts. Dr. Grover also uses antifibrotics with the XEN and trabeculectomy, Comparing continued from page 55 Implantation of the XEN Gel Stent; side photo demonstrates the external hand positioning during the implantation Source (all): Davinder Grover, MD but not with tubes. "I think you have to use MMC with a XEN," he said, "or it will fail." Potential complications Dr. Vinod said that one complica- tion with trabeculectomy and tubes is hypotony. Complications of hy- potony can include shallow anterior chamber and choroidal effusion, more often as a result of overfiltra- tion, but occasionally due to wound leaks. "Hypotony is usually transient and amenable to medical manage- ment but can sometimes be visually significant," she said. "Infectious complications resulting from wound leaks or tube erosion are less com- mon but can be devastating." Early studies of the XEN Gel Stent suggest that it is a fairly safe procedure with transient hypoto- ny occurring in less than 10% of patients, Dr. Vinod said. "However, the initial XEN studies did not use antifibrotics, and long-term data regarding late complications relating to mitomycin-C use, bleb scarring and failure, and effects on endotheli- al cell counts are unavailable for this relatively novel device," she said. A tube is a foreign body in the eye, and it does put the eye at risk of erosion and double vision, Dr. Grover said. The tough part with a trabeculectomy is it's a relatively invasive procedure, and there can be bleb-related problems, he said. Trab- eculectomy is also not as predictable as a tube because it depends on a number of factors, including the size of the flap, how you close the conjunctiva, and how it heals. With the XEN, there is a lower rate of erosion, and it does not put patients at risk for double vision. But it also has the predictability of a tube because it's a controlled outflow. "The other beauty of it is it does not require a conjunctiva dissection," Dr. Grover said. The XEN is placed ab interno, so you're not taking the conjunctiva down, he said, and it doesn't preclude you from doing a tube or trab later. Potential future procedures The success of a trabeculectomy or XEN Gel Stent relies on the availability of mobile conjunctiva/ Tenon's to facilitate bleb formation, Dr. Vinod said. In patients with a prior failed trabeculectomy, glau- coma surgeons may opt to perform a second trabeculectomy or a tube shunt, depending on the location and extent of conjunctival scarring. In the presence of a previously failed superotemporal trabeculectomy, she tends to place an inferonasal tube shunt. The XEN Gel Stent, Dr. Vinod said, is easier to place in previously operated eyes, as it is implanted ab interno and therefore doesn't require a conjunctival flap. However, sufficiently mobile conjunctiva is still needed for bleb formation. The superonasal quadrant is preferred as it is accessible via a temporal clear corneal incision and allows room for future incisional surgery if needed. Typically, Dr. Grover puts the XEN in the superonasal quadrant and leaves the superior quadrant for a possible trab and superotemporal quadrant for a tube. If you do a tra- beculectomy or tube and it fails, you can still do a XEN if the superonasal quadrant is untouched. The other thing that differentiates XEN, he said, is a faster visual recovery and faster recovery to activity. Phakic influence on procedure selection For phakic patients requiring very low intraocular pressure for disease stability, Dr. Vinod usually favors trabeculectomy as a primary sur- gery. "My decision to perform a trab, tube, or XEN in patients who are already pseudophakic depends on a variety of patient factors other than target IOP, including age, prior non-cataract ocular surgeries, ocular comorbidities likely to require surgical intervention in the future, ability to follow-up in the postop- erative period, etc.," she said. Like trabeculectomy and tube shunts, the XEN can be performed in conjunc- tion with cataract surgery in patients with visually significant cataract and glaucoma, she added, with the potential for fewer complications in the postoperative period than com- bining cataract surgery with a trab or tube. "Ultimately, lens status is one of several factors that influence my decision-making process when selecting the procedure that offers the best chance for disease stability and quality of life in my patients," Dr. Vinod said. EW Editors' note: Dr. Grover has financial interests with Allergan. Dr. Vinod has no financial interests related to her comments. Contact information Grover: dgrover@glaucomaassociates.com Vinod: kvinod@nyee.edu

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