Abstract and Introduction
Purpose: To evaluate the clinical outcomes of the new Ahmed glaucoma valve (AGV) model M4. The device consists of a porous polyethylene shell designed for improved tissue integration and reduced encapsulation of the plate for better intraocular pressure (IOP) control.
Methods: Medical records of patients with an AGV M4 implantation between December 1, 2012 and December 31, 2013 were reviewed. The main outcome measure was surgical failure, defined as either (1) IOP<5 mm Hg or >21 mm Hg and/or <20% reduction of IOP at last follow-up visit, (2) a reoperation for glaucoma, and/or (3) loss of light perception.
Results: Seventy-five eyes of 73 patients were included. Postoperative IOP at all follow-up visits significantly decreased from a baseline IOP of 31.2 mm Hg (P<0.01). However, IOP increased significantly at 3 months (20.4 mm Hg), 6 months (19.3 mm Hg), and 12 months (20.3 mm Hg) compared with 1 month (13.8 mm Hg) postoperatively (P<0.05). At 6 months and 1 year, the cumulative probability of failure was 32% and 72%, respectively.
Conclusions: The AGV M4 effectively reduced IOP in the first postoperative month, but IOP steadily increased thereafter. Consequently, failure rates were high after 1 year of follow-up.
In the past decade, there has been a rise in the usage of glaucoma drainage devices (GDDs) as the preferred surgical treatment for glaucoma.[1,2] In the Tube Versus Trabeculectomy study, tube shunts demonstrated a higher overall success rate at 1-, 3-, and 5-year follow-ups compared with trabeculectomies, indicating the efficacy of GDDs in managing glaucoma. In addition, tube shunts have been reported to have a lower incidence of early postoperative complications than trabeculectomies.[1,3–6] The Ahmed glaucoma valve (AGV; New World Medical Inc., Rancho Cucamonga, CA) has been widely used for patients with uncontrolled glaucoma and differs from other GDDs with a valve that theoretically permits unidirectional flow of aqueous humor at 8 mm Hg to prevent postoperative hypotony. Despite success,[7–11] the AGV also has its characteristic limitations. The AGV is associated with an increased likelihood of a hypertensive phase (HP), defined as a rise in intraocular pressure (IOP) >21 mm Hg within 6 months following glaucoma implant surgery.[12–16] In addition, AGVs require additional medication to achieve success relative to other GDDs.[7,13,17,18] Because of these limitations, the 1-year cumulative failure rate of the AGV can range from 4% to 43%.[19,20]
The recently launched AGV model M4 aims to address these limitations. In contrast to the polypropylene (S2) and silicone (FP7) glaucoma implants, the AGV M4 implant includes a porous polyethylene shell believed to permit the growth of collagen and blood vessels within the material and delay the fibrotic reaction around the plate.[21–24] The resulting low profile may lower the risk of diplopia. Kim et al have assessed the efficacy of the AGV M4 with a 80% cumulative probability of success in 1 year. Our study further evaluates the AGV M4 implant in a clinically diverse sample of glaucoma-affected eyes.
J Glaucoma. 2016;25(5):e475-e480. © 2016 Lippincott Williams & Wilkins