EyeWorld India December 2021 Issue

GLAUCOMA EWAP DECEMBER 2021 41 Michael S. Kook, MD Asan Medical Center 388-1 Songpa-Gu mskook@amc.seoul.kr ASIA-PACIFIC PERSPECTIVES W hen pharmacologic and/or laser trabeculoplasty fails to control intraocular pressure (IOP), IOP-lowering surgery is required in glaucoma management. Trabeculectomy is still considered the gold standard due to potent IOP lowering efficacy and cost-effectiveness worldwide to this date. In order to promote the efficacy and safety of trabeculectomy in the last five decades, the use of antimetabolites such as mitomycin-C (MMC) has been adopted, while a scleral flap is created at the trabeculectomy site to control aqueous outflow. Despite these attempts, trabeculectomy with MMC is often associated with undesirable postoperative short- and long-term complications, including hypotony, refractive changes, dellen formation, cataract, and endophthalmitis. Recent surgical advances have led to a new group of glaucoma operations aiming for less invasiveness and faster recovery of vision than trabeculectomy, while aiming to reduce postoperative complications. Microinvasive glaucoma surgery (MIGS) introduces a variety of interventions, extending from similar versions of trabeculectomy (e.g., Ex-Press, Preserflow MicroShunt) to minimally invasive shunt or bypass operations (e.g., XEN gel stent, iStent inject) which differ from trabeculectomy by way of limited surgical manipulation of the conjunctiva and/or sclera. Based on literature review, MIGS is generally safe and efficacious in terms of IOP lowering, despite there having been only a few MIGS that have been studied through randomized clinical trials. Moreover, only a few high-level studies exist comparing the surgical outcome of trabeculectomy and MIGS procedures. Schlenker et al. 1 compared the rate of surgical failure after trabeculecomy with MMC and XEN gel stent. They found no significant difference for surgical failure between the two procedures. However, another study by Wagner et al. 2 reported a higher rate of qualified success for trabeculectomy with MMC in a cohort of glaucoma patients in a typical clinical setting. The IOP reduction was higher in the trabeculectomy group (10.5 mmHg) compared to the XEN group (7.2 mmHg; p = 0.003) at the 12-month follow-up. Baker et al. 3 recently published the first prospective randomized multicenter study comparing Preserflow MicroShunt and trabeculectomy, both performed with MMC. They showed significantly higher surgical success rate for trabeculectomy and greater IOP-lowering after trabeculectomy compared with Preserflow MicroShunt. In the study, incidence of transient hypotony was higher in the trabeculectomy group versus the MicroShunt group (49.6% vs. 28.9%; p < 0.01). Therefore, current evidence may point toward a customized selection of glaucoma procedures (trabeculectomy vs. MIGS) considering patient’s demographic and clinical factors, including age, disease severity, lifestyle, and/ or socioeconomic status. References 1. Schlenker MB, et al. Efficacy, safety and risk factors for failure of standalone Ab interno gelatin microstent implantation versus standalone trabeculectomy. Ophthalmology . 2017;124:1579-1588. 2. Wagner FM, et al. Efficacy and safety of XEN –implantation vs. trabeculectomy: Dat of a “real-world” setting. . 2020;15:e0231614. 3. Baker ND, et al. Ab-Externo MicroShunt versus Trabeculectomy in Primary Open-Angle Glaucoma. Ophthalmology . 2021;Epub ahead of print. Editors’ note: Dr. Kook declared no relevant financial interests. wher e you create a flap instead of just making the punch,” he said. “At the time there were so many complications with full thickness procedures, cataract formation, hypotony, etc., the guarded filtration procedures became more popular because of the greater safety profile.” Evolution in technique Dr. Herndon and Dr. Rhee agreed that though there have been some slight adjustments to the technique, there hasn’t been much evolution in the procedure as it was initially presented. The main evolution, Dr. Herndon said, has been with antimetabolites and different techniques of applying mitomycin-C. He also mentioned how the technique has evolved for conjunctival dissection from limbal-based to fornix-based, the latter of which is more popular now. “What we do now isn’t exactly what was initially published/ studied, but it closely resembles it,” Dr. Rhee said. He added that in the 1970s and 1980s, there was some experimentation with different shapes and sizes of flaps, but it was determined that this didn’t make much of a difference. What did make a difference, he said, was in the early 1980s, when Heuer et al. published the 5-FU trial of the first antimetabolite, which was designed to inhibit scarring and improve the survivability of the trabeculectomy. 3 The next big advent, he said,