Comparison of safety and efficacy between silicone and polypropyIene Ahmed glaucoma valves in refractory glaucoma

Objective: To compare the safety and efficacy of polypropylene and silicone Ahmed glaucoma valves (AGVs) over 1 year of follow-up. Design: Retrospective comparative study. Participants: Fifty consecutive patients with polypropylene and 49 consecutive patients with silicone AGV implantation. Methods: 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 >= 20% and a final IOP of > 5 and < 22 mmHg, without additional surgical intervention for IOP control, loss of light perception, or serious complications. Main Outcome Measures: The 2 groups were compared for IOP control, visual outcome, complication rate, and surgical success rate. Results: 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 >= 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). Conclusion: 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.