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Editorial Glaucoma The Ahmed Versus Baerveldt (AVB) Study Panos G Christakis and Iqbal I K Ahmed Department of Ophthalmology and Vision Sciences, University of Toronto Faculty of Medicine, Toronto, Canada G laucoma drainage devices are being increasingly used in the treatment of advanced glaucoma refractory to medical therapy or in cases that have failed trabeculectomy with antimetabolite. The Ahmed Versus Baerveldt (AVB) Study is an international, multicenter, randomized clinical trial comparing the two most frequently used devices. Five-year results have been recently published providing high quality evidence to guide a surgeon’s decision on which device to use. Keywords Glaucoma drainage devices, aqueous shunts, Ahmed valve, Baerveldt tube, surgery Disclosure: Iqbal I K Ahmed has received personal fees from Abbott Medical Optics and New World Medical. Panos G Christakis has nothing to disclose in relation to this article. No funding was received in the publication of this article. The Ahmed Versus Baerveldt study was funded by a research grant from the Glaucoma Research Society of Canada and a departmental challenge grant from Research to Prevent Blindness. This article is a short opinion piece and has not been submitted to external peer reviewers but was reviewed by the editorial board for accuracy before publication. Authorship: All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship of this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, adaptation, and reproduction provided the original author(s) and source are given appropriate credit. Received: January 11, 2017 Published online: February 17, 2017 Citation: US Ophthalmic Review, 2017;10(1):21–2 Corresponding Author: Iqbal K Ahmed, Department of Ophthalmology and Vision Sciences, University of Toronto Faculty of Medicine, 340 College Street, Suite 400, Toronto, ON M5T 3A9, Canada. E: ike.ahmed@utoronto.ca The treatment of glaucoma usually begins with the use of topical antiglaucoma medications or laser trabeculoplasty, with surgery reserved for cases refractory to, or at high-risk of failing medical management. 1 Trabeculectomy with antimetabolite has traditionally been considered the preferred first-line filtration procedure. 1 However, failure rates of approximately 50% at 5 years have been reported, as well as complications including hypotony, wound leak, and infection. 2,3 Furthermore, 5-year results of the Tube Versus Trabeculectomy (TVT) Study found Baerveldt implantation had a higher success rate and lower rate of reoperation that trabeculectomy, with a similar intraocular pressure (IOP) reduction and need for glaucoma medications. 3 As a result, there has been a significant change in practice patterns over the past two decades, with declining rates of trabeculectomy and an increase in the use of glaucoma drainage devices. 4 In particular, glaucoma drainage devices are being increasingly used in patients who have failed trabeculectomy, or who have disease at high risk of failing trabeculectomy (e.g. neovascular or uveitic glaucoma). 5 The two most frequently used glaucoma drainage devices are the Ahmed valve implant (New World Medical Inc, Rancho Cucamongo, CA, US) and the Baerveldt implant (Abbott Medical Optics, Santa Ana, CA, US). These devices differ in that the Ahmed implant has a venturi-based valve system which opens at 8–10 mmHg and serves to prevent hypotony and its related complications. The Baervedlt implant lacks a built-in form of flow restriction and requires the surgeon to ligate the tube intraoperatively until adequate scar tissue has formed around the end-plate to regulate flow. Data comparing these devices is limited by its retrospective nature, differing patient populations and outcome criteria. As a result, selecting which glaucoma drainage device to use has largely been driven by surgeon experience and clinical site preference. 6–9 The Ahmed Versus Baerveldt (AVB) Study is an international, multicenter, randomized clinical trial comparing these devices. 10–13 A total of 238 patients were enrolled from six clinical centers and randomized to receive either an Ahmed-FP7 valve implant or a Baerveldt-350 implant. Patients had uncontrolled glaucoma despite maximum tolerated medical therapy, with a mean preoperative IOP of 31 mmHg on three glaucoma medications. Trabeculectomy had failed in 37% of patients, and many patients had disease at high risk of failing trabeculectomy including 21% with neovascular glaucoma and 10% with uveitic glaucoma. Due to the advanced disease of the study group, a strict IOP target of 5–18 mmHg was used based on data suggesting IOP >18 mmHg may result in progression. 14 Both devices were effective in lowering IOP and the need for glaucoma medications. At 5 years, the mean IOP was 16.6 mmHg in the Ahmed group (47% reduction) and 13.6 mmHg in the Baerveldt group (57% reduction, p=0.001). Mean medication use was 1.8 in the Ahmed group (44% reduction) and 1.2 in the Baerveldt group (61% reduction, p=0.03). De novo glaucoma surgery was required in 18% of the Ahmed group and 11% of the Baerveldt group (p=0.22). The 5-year cumulative failure rate was 53% in the Ahmed group and 40% in the Baerveldt group (p=0.04). Hypotony resulted in failure in five patients TOU CH MED ICA L MEDIA 21