Ab-Externo MicroShunt versus Trabeculectomy in Primary Open-Angle Glaucoma:5-Year Safety Results from a Randomized, Multicenter Study.

Purpose: To compare the long-term safety of MicroShunt implantation with trabeculectomy in eyes with primary open-angle glaucoma (POAG).

Methods: This was a 3-year observational extension of a 2-year prospective randomized trial comparing clinical outcomes of MicroShunt implantation with trabeculectomy, both augmented with mitomycin C. Adverse events (AEs), intraocular pressure (IOP), and IOP-lowering medication use were recorded 36, 48, and 60 months after initial randomization. The primary outcome was the cumulative incidence of sight-threatening AEs. Secondary outcomes included all other AEs/complications, secondary interventions, and reductions in IOP and number of glaucoma medications.

Results: The extension study enrolled 279 patients (217 MicroShunt, 62 trabeculectomy), with 256 (198 and 58, respectively) completing the month 60 visit. Rates of sight-threatening AEs were 2% (n=4) in the MicroShunt group and 0% in the trabeculectomy group, with one eye each in the MicroShunt group having central retinal artery occlusion, choroidal hemorrhage (following placement of a glaucoma drainage device), progressive endothelial cell loss, and pseudophakic bullous keratopathy. Only two of the four sight-threatening AEs in the MicroShunt group were deemed related to the study device or procedure. Four eyes in the MicroShunt group experienced device erosion through the conjunctiva. Increased IOP requiring treatment was more frequent (26% versus 8%, P=0.0017), whereas hypotony (3% versus 13%, P=0.038), epiretinal membrane formation (2% versus 8%; P=0.028), and blepharoptosis (4% versus 11%, P=0.048) were less frequent, in the MicroShunt group. Four patients in the trabeculectomy group required surgical revision for hypotony. Changes in endothelial cell density were similar in the MicroShunt (-19% ± 22%) and trabeculectomy (-19% ± 22%) groups, with a mean between-group difference of 0.1% (P=0.98). Mean ± SD IOP was reduced from 20.8 ± 4.9 mmHg at baseline to 14.2 ± 4.1 mmHg at month 60 in MicroShunt eyes (mean reduction, 5.5 mmHg [26%]) and from 20.1 ± 3.9 mmHg to 10.4 ± 3.7 mmHg in trabeculectomy eyes (mean reduction, 9.1 mmHg [45%]), with a between-group difference of -4.6 mmHg (P<0.0001).

Conclusion: Both filtering procedures demonstrated favorable safety profiles over 5 years. Most AEs through 5 years did not necessitate reoperation nor result in vision-threatening complications.