Comparison of Safety and Efficacy between Silicone and Polypropylene Ahmed Glaucoma Valves in Refractory Glaucoma

Abstract

To compare the safety and efficacy of polypropylene and silicone Ahmed glaucoma valves (AGVs) over 1 year of follow-up. Retrospective comparative study. Fifty consecutive patients with polypropylene and 49 consecutive patients with silicone AGV implantation. Our hospital instituted a formulary conversion of the glaucoma aqueous drainage device from polypropylene to silicone AGVs in January 2003. We reviewed the polypropylene AGVs within 7 months before and the silicone AGVs within 7 months after the date of conversion performed on patients with glaucoma refractory to medical treatment and filtering procedures, without previous drainage devices or cyclodestructive procedures, and with a minimum of 12 months' follow-up. Surgical success was defined as an intraocular pressure (IOP) reduction of > or =20% and a final IOP of >5 and <22 mmHg, without additional surgical intervention for IOP control, loss of light perception, or serious complications. The 2 groups were compared for IOP control, visual outcome, complication rate, and surgical success rate. Significant IOP reductions occurred after polypropylene AGV implantation (from 32.4+/-11.3 mmHg to 16.5+/-6.9 mmHg, P<0.0001) and silicone AGV implantation (from 32.6+/-12.6 mmHg to 14.7+/-6.9 mmHg, P<0.0001). The silicone group had a lower mean IOP than the polypropylene group at all postoperative visits, but the differences were significant only at 3 months postoperatively (P = 0.014). In addition, the silicone group was associated with a rate of insufficient IOP control as the reason of failure (IOP of > or =22 mmHg or IOP reduction of <20%) lower (4.1%) than that of the polypropylene group (20.0%, P = 0.015), but a rate of non-tube related serious complications (16.3%) higher than that of the polypropylene AGV (4.0%, P = 0.042). After 1 year of follow-up, the silicone AGV is at least as effective as the polypropylene AGV in IOP reduction but may be associated with a higher rate of complications. These differences are important for surgeons converting to use of the silicone AGV in patients with glaucoma refractory to other forms of treatment.