EyeWorld Asia-Pacific December 2016 Issue

December 2016 58 EWAP GLAUCOMA The XEN Gel Stent is preloaded in a disposable injector with a 27-gauge needle. Using an ab interno approach, the gel stent is delivered into the non-dissected Tenon space, creating a permanent connection from the anterior chamber to the subconjunctival space. Source: Allergan New tool for surgical IOP reduction by Tony Realini, MD, MPH Physicians shared their early experiences with the XEN Gel Stent at the 2016 European Glaucoma Society meeting O ne of the greatest unmet needs in clinical glaucoma management is for an operation highly effective in lowering intraocular pressure (IOP) while having a highly favorable safety profile. Traditional glaucoma filtering surgeries—such as trabeculectomy and tube shunt procedures—deliver unrivaled efficacy but with significant potential risks. In contrast, the various microinvasive glaucoma surgery (MIGS) procedures that have emerged in recent years provide a more favorable safety profile, but are generally unable to consistently deliver low target IOP outcomes similar to filtration surgery. Among the devices and procedures vying to meet this unmet need is the AqueSys XEN Gel Stent (Allergan, Dublin). The device is not yet available in the U.S., but has been approved in Europe. Early experience with the device was presented at the recent biennial meeting of the European Glaucoma Society in Prague. Device “The XEN gel implant is a minimally invasive, noninflammatory subconjunctival porcine-derived gelatin implant that has been developed to provide long-term IOP lowering in glaucoma, whether used alone or in combination with cataract surgery,” said Keith Barton, MD , London. The device is a flexible tube packaged on a preloaded injector, inserted via an ab interno approach, that is inserted through the trabecular meshwork and sclera into the subconjunctival space, he said. This allows aqueous fluid to flow from the anterior chamber into the subconjunctival space, bypassing the trabecular outflow pathway, which becomes impaired in primary open-angle glaucoma. The internal diameter of the tube is 45 microns, which generates a degree of flow resistance intended to prevent IOP from falling below the 5 to 8 mmHg range, thus minimizing the risk of postoperative hypotony, he added. Clinical study design Dr. Barton presented the results of an international, prospective, nonrandomized, open-label study conducted in patients with moderate POAG whose IOP fell between 18 and 33 mmHg while using one to four IOPlowering medications. The study was sponsored by the manufacturer. “The gel implant was placed either as a solo procedure or in combination with cataract surgery,” he said. “Both eyes could be treated if eligible, and fellow eye surgeries were performed at least 30 days apart.” Overall, 111 eyes had device implantation alone, while another 104 underwent implantation combined with cataract surgery. Subjects were predominantly Caucasian and female with an average age of 73 years and mean baseline IOP of 21.4 mmHg. The primary outcomes were reduction in both IOP and the number of IOP-lowering medications used 12 months postoperatively. Study results Once past the initial postoperative period, when IOP can be variable and not related to long-term outcomes, mean IOP reductions from months 3 to 12 ranged from 28.4 to 34.1% from the preoperative baseline, with mean IOP reduction of 7.6+4.8 mmHg at month 12, Dr. Barton said. “In addition,” he said, “there was a reduction in the mean number of IOP- lowering medications from 2.6 preoperatively to 0.6 at month 12.” The most common intraoperative complication was bleeding into the anterior chamber, which affected 2.8% of eyes, he said. Postoperatively, the most common adverse event was transient hypotony, noted in 15% of eyes on the first postoperative day, but this resolved without intervention in all cases but one, which required reformation of the anterior chamber with viscoelastic. Other significant adverse events included conversion to alternative IOP-lowering procedures in 5.1% of cases and two serious adverse events related to prolonged hospitalizations, one following conversion to trabeculectomy and the other requiring device explantation, Dr. Barton said. Bleb needling was required in nearly 25% of cases, resulting in mean IOP reductions from 21.1 mmHg before needling to 14.5 mmHg after needling. Standalone implantation Cataract surgery alone is well known to lower IOP, especially in patients with open-angle glaucoma. In this study, however,