When Ahmed Glaucoma Valves Fail, A Second Implant Can Still Lower IOP

In eyes with a failed Ahmed glaucoma valve (AGV), implantation of a second Ahmed glaucoma valve (re-AGV) and capsulectomy shunt revision (CSR) are both effective treatment options for reducing intraocular pressure (IOP); however, re-AGV is more effective than the CSR, reducing IOP at all time points of the study and yielding a higher success rate after 12 months, research published in Ophthalmology Glaucoma shows.

Researchers conducted a quasi-experimental study to compare the efficacy of CSR with that of re-AGV in glaucoma patients with failed shunts. All first AGVs had been implanted in the superotemporal quadrant. The team assigned patients to undergo CSR or re-AGV based on the appearance and accessibility of the existing AGV and the feasibility for re-AGV in other quadrants (either the supranasal or infranasal quadrants). 

The study’s primary outcome was surgical success, defined as IOP higher than 5 mm Hg, but no higher than 21 mm Hg, IOP reduction of 20% from baseline or more, and no reoperation for glaucoma. Its secondary outcomes were IOP, number of glaucoma medications, and complications during the 12-month follow-up period. The researchers evaluated IOP at baseline and 1, 2, 3, 6, 9, and 12 months after CSR/re-AGV.

A total of 46 eyes of 46 patients were included in the study (CSR, n=25; median age, 23.5 years; range, 4-70; re-AGV, n=21; median age, 14 years; range, 3-67). The researchers found no significant difference between the groups regarding initial diagnoses, type of glaucoma, number and type of prior surgeries, and the time interval between primary AGV implantation and the second procedure (33 months in CSR group vs 38 months in re-AGV group; P =.1). 

The team found that mean IOP was significantly lower than preoperative values at all time points in both study groups. They reported that IOP decreased significantly from 28.3±5.04 mm Hg at baseline to 16.4 ± 2.4 mm Hg at final follow-up in capsulectomy group (P =.002) and from 30.99±6.2 to 13.6±3.8 mm Hg, respectively, in the re-AGV group (P =.001). They found that IOP was significantly higher in the CSR group than the re-AGV group at all postoperative visits. 

The researchers reported that the median number of glaucoma medications at baseline was 3.3±0.5 and 3.1±0.6 in the CSR and re-AGV groups, respectively (P =.223). They found that the CSR group required a significantly higher number of glaucoma medications than the re-AGV group at postoperative month 1 (2.3±0.2 vs 1.8±0.5; P =.048) but found no significant difference in the number of medications between the groups at the 3-, 6-, 9- and 12-month follow-up visits.

The team found that the cumulative probability of success at 12 months was significantly higher in the re-AGV group (87.5% vs 53.3%; P =.002). They observed no significant difference in the overall complications rate between the study groups. 

“Our study is the first head-to-head report comparing CSR to repeat AGV implantation,” according to the researchers. “Although capsulectomy seems inferior to repeat AGV, it effectively and significantly reduces IOP after failed primary AGV. It may be considered a viable option in the eyes with an extensive conjunctival scar before proceeding to less attractive options such as CPC or as a temporizing measure to delay a second shunt procedure with its possible risks of poor cosmesis, ocular dysmotility, and corneal decompensation.”

Limitations of the study included its non-randomized nature, modest sample size, and limited follow-up duration.