Long-Term Visual Field Outcomes after failed trabeculectomy: Same site Trabeculectomy versus Ahmed Glaucoma Valve Implantation.

Purpose

To compare visual field (VF) progression rates after repeat trabeculectomy versus Ahmed Glaucoma Valve (AGV) implantation in eyes with prior trabeculectomy failure, and to identify risk factors for postoperative VF deterioration.

Design

Retrospective clinical cohort study.

Methods

Eyes with failed trabeculectomy that underwent AGV implantation or repeat trabeculectomy were included if they had ≥4 postoperative VF tests and ≥2 years of follow-up. VF progression was assessed using mean deviation (MD) slope, Glaucoma Rate Index (GRI), and pointwise linear regression (PLR). An eye was defined as progressing if two or more VF methods agreed. In a subset of patients with sufficient preoperative data, VF progression rates before and after surgery were compared.

Results

A total of 186 eyes were included (94 trabeculectomy, 92 AGV). Both procedures significantly reduced intraocular pressure (IOP) (P < 0.001), with lower postoperative IOP and fewer medications in the trabeculectomy group (P < 0.001). VF progression by two or more methods occurred in 35% of AGV eyes and 31% of trabeculectomy eyes (P = 0.6). Median MD rates of decline were -0.43 dB/year in the AGV group and -0.29 dB/year in the trabeculectomy group (P = 0.9). In the comparison of VF rates before and after surgery, progression rates were reduced more by trabeculectomy than AGV implantation (P = 0.03). Higher postoperative peak IOP was associated with an increased risk of VF deterioration (11% per mmHg).

Conclusions

Postoperative VF progression was similar between AGV implantation and repeat trabeculectomy; however, trabeculectomy reduced VF progression rates more than AGV implantation compared with preoperative rates. Postoperative peak IOP, not mean IOP, was an important risk factor for VF deterioration. Trabeculectomy achieved greater IOP reduction, including reduction of IOP peak, than AGV implantation. Repeat trabeculectomy should be considered a viable surgical option in patients who have failed an initial trabeculectomy.