Failed Ahmed glaucoma valves: trabeculectomy versus repeat shunt surgery

Abstract

IntroductionTo investigate the outcomes of trabeculectomy (TRAB) versus repeat Ahmed glaucoma valve (re-AGV) implantation in eyes with Ahmed glaucoma valve (AGV) failure.MethodsThis quasi-experimental study includes patients with failed AGV implants requiring additional surgical intervention between 2018 and 2022. Patients in the TRAB group underwent a fornix-based procedure with mitomycin C 0.01% injection (0.1 mL). Eyes in the re-AGV group underwent repeat shunt surgery. The choice of the procedure was based on conjunctival condition. The primary outcome measure was surgical success rate based on various intraocular pressure (IOP) targets and percentages of IOP reduction from baseline: IOP ≤ 21 mmHg and 20% reduction (conventional criteria), IOP ≤ 18 and > 20% reduction (criterion A), IOP ≤ 15 and > 25% reduction (criterion B), and IOP ≤ 12 and > 30% reduction (criterion C).ResultsForty-eight eyes of 48 patients were operated and reported herein, consisting of 22 eyes of 22 patients undergoing TRAB and 26 eyes of 26 subjects undergoing re-AGV. No significant difference was observed between the study groups in terms of initial diagnoses, baseline IOP or the number of prior surgeries. The cumulative probability of survival at one year was significantly higher in the trabeculectomy group using the three stricter success definitions. In both study groups, IOP was significantly reduced from baseline at all postoperative visits, and was significantly lower in the TRAB group at all time points beyond one month. At 12 months, 5% of TRAB versus 48% of re-AGV eyes required glaucoma medications (P < 0.001). The rate of complications was comparable between the study groups (P = 0.76) but there was a trend toward a greater need for repeat surgery in the re-AGV group (4 eyes versus nil, P = 0.07).ConclusionsTrabeculectomy can be considered a safe and effective surgical option in eyes with failed AGV leading to significantly lower IOP levels and more favorable success rates than re-AGV in selected patients.