Efficacy of ab-interno gelatin microstent implantation in primary and refractory glaucoma

Objective: To evaluate the outcomes of ab interno gelatin microstent implantation alone and in combination with phacoemulsification for the reduction of intraocular pressure (IOP). Design: Retrospective cohort study. Participants: 141 eyes of 141 patients with any glaucoma subtype, including refractory glaucoma, operated in the Centre Hospitalier de l'Université de Montréal (CHUM) from 2015-2018. Patients were included if they were over 40 years of age and had a preoperative IOP of >18 mm Hg on maximum tolerated medical therapy. Methods: All patients received ab-interno microstent implantation (XEN-45, Allergan, Madison, NJ) with mitomycin C +/- combined phacoemulsification. The primary outcome was complete surgical success (IOP 6-18 mm Hg and <20% reduction from baseline without IOP medications or reoperations or cyclophotocoagulation); secondary outcomes included qualified success allowing for medications, percentage reduction in mean IOP and medications, and reduction in number of complications, interventions, and reoperations. Results: Mean follow-up was 30.5 ± 10.2 months (±SD). Mean IOP was 23.3 ± 7.0 mm Hg on 3.4 ± 0.8 medications at baseline and 13.3 ± 4.7 mm Hg on 1.9 ± 1.5 medications at 24 months of follow-up (p < 0.001). From 24-month survival analysis estimates, complete success was achieved in 34.1% of microstent eyes versus 20.7% with combined phacoemulsification (p = 0.02); 79.1% versus 75.1% achieved qualified success, respectively (p = 0.86). Cases with combined phacoemulsification had a higher rate of failure (hazard ratio [HR] = 1.6, 95% CI 1.1–2.3, p = 0.02). Needling with mitomycin-C or 5-fluorouracil postoperatively occurred in 54 eyes (38.3%). Complications included transient hypotony (10.6%), transient hyphema (6.4%), macular edema (4.3%), and microstent exposure (2.8%). There were 33 eyes (23.4%) with reoperations and 14 (9.9%) requiring subsequent cyclophotocoagulation lasers. Conclusions: Microstent implantation required topical therapy in most cases 24 months following surgery in primary and refractory glaucoma and, when combined with phacoemulsification, had a higher risk of failure.