Comparison of silicone and polypropylene Ahmed glaucoma valves: two-year follow-up

To compare the safety and efficacy of silicone and polypropylene Ahmed glaucoma drainage devices. We studied a retrospective consecutive case series of 91 eyes of 81 patients who were implanted with Ahmed valves by a single surgeon (R.M.S.). The first 43 eyes received polypropylene (model S2) valves; the remaining 48 eyes received silicone (model FP7) valves. Data collection included demographics, type of glaucoma, and sequential measurement of clinical characteristics. The mean outcome measures were visual acuity, intraocular pressure (IOP), number of antiglaucoma medications, and postoperative complications. Data were collected on day 1; weeks 1, 2-3, and 6; months 3-4, 6, and 12; and last visit. Mean follow-up was 27.1 months for the polypropylene valve and 20.1 months for the silicone valve. Mean decrease in IOP at 1 year was significantly greater in the silicone group than in the polypropylene group (t test, p < 0.005); however, this difference disappeared at 2 years. There were no differences between the groups in visual acuity, number of antiglaucoma medications, bleb needlings with 5-fluorouracil, or minor complications. A greater number of serious complications, including valve failures, occurred in the polypropylene group than in the silicone group, and this difference could not be accounted for by the longer follow-up in the polypropylene group. At 2 years follow-up, 82% of patients with silicone valves and 72% of patients with polypropylene valves continued to achieve greater than 30% IOP reduction. Both the silicone and polypropylene Ahmed valves significantly reduced IOP over 2 years. The silicone valve was associated with fewer serious complications.