Efficacy of the Ahmed S2 Glaucoma Valve compared with the Baerveldt 250-mm2 Glaucoma Implant

Objective: To compare the efficacy of the Ahmed S2 Glaucoma Valve with the Baerveldt 250-mm(2) Glaucoma Implant in the treatment of adult glaucoma. Design: Comparative case series. Participants: Fifty-nine eyes of 59 patients who received the Ahmed S2 Glaucoma Valve and 133 eyes of 133 patients who received the Baerveldt 250-mm2 Glaucoma Implant by the Indiana University Glaucoma Service from 1996 to 2003. Methods: Eyes that had previous drainage implant procedures were excluded from both groups. If both eyes of a single patient received an implant, the second eye to undergo implantation was excluded from the study. Main Outcome Measures: Kaplan-Meier survival with success defined as intraocular pressure (IOP) > 5 mmHg and < 22 mmHg and at least 20% reduction from preoperative IOP (with or without antiglaucoma medications) and without loss of light perception. Secondary outcome measures included intraocular pressure, visual acuity, number of glaucoma medications, and surgical complications. Results: The 2 groups were similar with regards to age, gender, race, neovascular glaucoma diagnosis, number of prior ocular surgeries, preoperative IOP, and number of preoperative glaucoma medications. Mean durations of follow-up were 20.0 months for Ahmed eyes and 22.9 months for Baerveldt eyes. Cumulative successes in the Ahmed group were 0.73 at 1 year and 0.62 at 2 years, whereas cumulative successes in the Baerveldt group were 0.92 at 1 year and 0.85 at 2 years (Kaplan-Meier survival functions: P = 0.03, log rank test). Male gender, African descent, neovascular glaucoma, and Ahmed implantation were found to be significant predictors of failure. At last follow-up visit, eyes in the Ahmed group had a significantly higher mean IOP (19.8 +/- 9.5 vs. 15.8 +/- 7.9 mmHg, P = 0.003, t test) and more antiglaucoma medications (1.4 +/- 1.2 vs. 0.9 +/- 1.1 medications, P = 0.008, Mann-Whitney test) than eyes in the Baerveldt group. Two methods for avoiding hypotony after Baerveldt 250-mm(2) implantation had similar outcomes. Conclusions: Our study suggests that the Ahmed S2 Glaucoma Valve may be less effective at lowering IOP than the Baerveldt 250-mm(2) Glaucoma Implant.