Fibrous ingrowth: an overlooked cause of Ahmed Glaucoma Valve failure

To highlight fibrous ingrowth (FI) into the Ahmed Glaucoma Valve (AGV) mechanism as a previously under-recognized cause of late AGV failure.

In this prospective interventional case series, 40 eyes of 40 patients with failed AGVs underwent capsulectomy shunt revision (CSR) between September 2022 and October 2024. The cohort included a high proportion of congenital and juvenile glaucoma cases, reflecting the tertiary referral nature of our center. Intraoperatively, the AGV valve mechanism was thoroughly explored, with special attention to identifying growth of fibrous tissue into the valve chamber. After the procedures, patients were stratified into two groups: those with fibrous ingrowth (FI-CSR) and those without abnormal ingrowth (CSR). Pre- and postoperative intraocular pressure (IOP), number of medications, complications and surgical success were reported. Histopathologic evaluation was performed on the excised tissue in the FI-CSR group.

FI was identified in 30% (12/40) of all operated eyes. Patients in the FI-CSR group were significantly older (26.3 ± 20.4 versus 16.6 ± 10.2 years old, P = 0.049) and had undergone a larger number of prior surgeries (3.8 ± 1.3 versus 2.1 ± 1.3 procedures, P < 0.001). The prevalence of primary congenital glaucoma (PCG) was also significantly higher in the FI-CSR group as compared to the CSR group (8/12 [66.7%] versus 11/28 [39.3%] cases respectively, P < 0.001). At 12 months after surgical revision, mean IOP decreased from 28.1 ± 6.8 mmHg to 15.1 ± 2.1 mmHg in the FI-CSR group (P < 0.001) and from 28.1 ± 5.9 to 16.9 ± 4.4 mmHg in the CSR group (P < 0.001). Final IOP and surgical success rates at 12 months were comparable between the two groups. No vision-threatening complications were observed during the follow-up period. Histopathologic evaluation of the excised FI tissue revealed dense fibrovascular tissue with chronic inflammation.

Fibrous ingrowth into the AGV valve chamber is a significant but often overlooked cause of AGV failure. Surgical excision of FI during CSR was associated with restored device function and improved IOP control with outcomes comparable to conventional CSR. Exploration of the valve mechanism for detection and removal of FI is beneficial during revision procedures in eyes with failed AGVs and could avoid more invasive interventions.