Ab Externo SIBS Microshunt with Mitomycin C for Open-Angle Glaucoma: Three-Year Results as a Primary Surgical Intervention

Abstract

To determine the effectiveness, risk factors for surgical failure and adverse events in a large cohort of patients receiving standalone ab externo SIBS microshunt implantation with mitomycin C (MMC) over 3-years of follow-up. Retrospective, interventional case series. Glaucomatous eyes on maximally tolerated medical therapy with no previous subconjunctival glaucoma surgery. Records of eyes that underwent ab externo SIBS microshunt with MMC between July 2015 to November 2017 were reviewed. Data from all follow-up visits were utilized and included IOP, medication use, post-operative interventions, complications, and reoperations. The primary outcome was proportion of eyes at 3-years with (1) no 2 consecutive IOPs >17mmHg (or <6mmHg with >2 lines of vision loss from baseline); (2) ≥20% reduction from baseline IOP; and (3) using no glaucoma medications (complete success). Secondary outcomes included 14 and 21mmHg upper IOP thresholds with and without ≥20% IOP reduction from baseline, qualified success (with glaucoma medications), risk factors for failure, median IOP/medications, post-operative interventions, complications, and reoperations. One hundred fifty-two eyes from 135 patients were included. Complete and qualified success was achieved in 55.6% and 74.8% of eyes, respectively. Time to first glaucoma medication use was a median of 16.9 (IQR 12.1-34.1) months, however 59.4% of eyes remained medication free at 3-years. Significant risk factors for failure included receiving <0.4mg/mL of MMC (adjusted HR 2.35; 95% CI 1.43-3.86) and baseline IOP <21mmHg (adjusted HR 1.84; 95%CI 1.09-3.08). The most common complications were choroidal detachment, hyphema and anterior chamber shallowing, occurring in 7%, 5% and 5% of eyes respectively. The needling rate was 15.1%, with significantly higher frequency for baseline IOP >21mmHg (HR 3.21, 95% CI 1.38 - 7.48). Revisions occurred in 7% of eyes, and reoperations in 3%. Eyes receiving <0.4mg/mL of MMC underwent more revisions (OR 4.9; 95%CI 1.3-18.3). Three-year follow up data from this large cohort continues to support promising rates of qualified and complete success, with decreased medication burden post-operatively and few post-operative complications and interventions. Comparisons to other filtering surgeries will further facilitate integration of the SIBS microshunt into the surgical treatment paradigm.