Ab-Externo MicroShunt versus Trabeculectomy in Primary Open-Angle Glaucoma: One-Year Results from a 2-Year Randomized, Multicenter Study

Abstract

To compare the effectiveness and safety of the MicroShunt versus trabeculectomy in patients with primary open-angle glaucoma (POAG). One-year results from a 2-year, prospective, randomized, multicenter, noninferiority study (NCT01881425) conducted in the United States and Europe. Eligible patients were aged 40-85 years with intraocular pressure (IOP) ≥15 and ≤40 mmHg and mild-to-severe POAG inadequately controlled on maximum tolerated medical therapy. Patients were randomized 3:1 to undergo stand-alone MicroShunt implantation or trabeculectomy, both performed with adjunctive mitomycin C (0.2 mg/ml for 2 minutes). The primary effectiveness end point was surgical success, defined as ≥20% reduction in mean diurnal IOP from baseline (no medication washout) at year 1 without increasing the number of glaucoma medications. Secondary effectiveness end points at year 1 were the mean IOP change from baseline and requirement for postoperative intervention. Additional end points included glaucoma medication use and adverse events. Overall, 395 (MicroShunt) and 132 (trabeculectomy) patients were randomized (mean Humphrey visual field mean deviation,-12.34 decibels [dB]). At year 1, probability of success was lower in the MicroShunt group compared with the trabeculectomy group (53.9% vs. 72.7%, respectively; P < 0.01). In the MicroShunt group, mean IOP ± standard deviation decreased from 21.1 ± 4.9 mmHg at baseline to 14.3 ± 4.3 mmHg (-29.1%; P < 0.01) at year 1, with a mean of 0.6 ± 1.1 glaucoma medications (baseline 3.1 ± 1.0; P < 0.01). In the trabeculectomy group, mean IOP decreased from 21.1 ± 5.0 mmHg to 11.1 ± 4.3 mmHg (-45.4%; P < 0.01), with a mean of 0.3 ± 0.9 glaucoma medications (baseline 3.0 ± 0.9; P < 0.01). Postoperative interventions, including laser suture lysis, were reported in 40.8% (MicroShunt) versus 67.4% (trabeculectomy) of patients (P<0.01). Reported incidence of transient hypotony was higher in the trabeculectomy group versus the MicroShunt group (49.6% vs. 28.9%; P < 0.01). Vision-threatening complications were uncommon and reported in 1.0% of MicroShunt versus 0.8% of trabeculectomy patients. Probability of success was lower with MicroShunt compared with trabeculectomy. Although reductions in IOP and glaucoma medications over 1 year were observed in both groups, the trabeculectomy group had a lower mean IOP on fewer medications.