Long-Term Visual Field Outcomes After Failed Trabeculectomy: Same-Site Trabeculectomy Versus Ahmed Glaucoma Valve...

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

Retrospective clinical cohort study.

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 slope, Glaucoma Rate Index, and pointwise linear regression. An eye was defined as progressing if 2 or more VF methods agreed. In a subset of patients with sufficient preoperative data, VF progression rates before and after surgery were compared.

A total of 186 eyes were included (94 trabeculectomy and 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 2 or more methods occurred in 35% of AGV eyes and 31% of trabeculectomy eyes (P = 0.6). Median mean deviation 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 mm Hg).

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.