The Ahmed shunt versus the Baerveldt shunt for refractory glaucoma: A single-surgeon comparison of outcome

Purpose: To compare the surgical outcome of Baerveldt and Ahmed shunt implants in the treatment of refractory glaucoma. Design: Retrospective, nonrandomized, comparative trial. Methods and Participants: Medical records of 118 consecutive patients who underwent glaucoma shunt implantation (70 Baerveldt, 48 Ahmed) by a single surgeon were reviewed. Main Outcome Measures: The primary outcome measure was surgical success (6 mmHg ≤ intraocular pressure [IOP] ≤ 21 mmHg without additional glaucoma surgery or devastating complication) at 12 months after surgery. Secondary outcome measures included mean IOP and number of medications used at the following postoperative visits: day 1, 1 week, 1 month, 3 months, 6 months, and every 6 months thereafter. Additional outcome measures evaluated include visual acuities, prevalence and timing of postoperative choroidal detachment, and clinical bleb encapsulation. Results: Survival curve analysis showed success rates of 82.9% of the Ahmed group and 72.9% of the Baerveldt group at 12 months after surgery (P = 0.257). Patients in the Ahmed group exhibited lower IOPs at 1 day (P < 0.001) and 1 week (P < 0.001) after surgery and were taking fewer glaucoma medications at 1 week (P < 0.001) and 1 month (P < 0.001) after surgery. A higher proportion of Ahmed patients experienced clinical bleb encapsulation than did the Baerveldt patients (60.4% vs. 27.1%; P < 0.001). Moreover, the first observation of postoperative bleb encapsulation was sooner after surgery for the Ahmed patients (50.0 ± 43.8 days) than for the Baerveldt patients (69.8 ± 22.6 days; P = 0.001). Conclusions: The Ahmed shunt implant exhibited better control of IOP in the early postoperative period (1 day and 1 week) with patients requiring fewer glaucoma medications at 1 week and 1 month after surgery. There was both a higher prevalence and earlier onset of bleb encapsulation observed with the Ahmed shunt implant.