Author’s Name(s): Ahmed Abdelaal, Ticiana De Francesco, Ingeborg Stalmans, Francesco Oddone, Markus Lenzhofer, Herbert Reitsamer, Antonio Fea, David Yan, Moulin-Romsee Marie-Isaline, Iqbal (Ike) Ahmed 

Author’s Disclosure Block: Ahmed Abdelaal: none; Ticiana De Francesco: none; Ingeborg Stalmans: none; Francesco Oddone: none; Markus Lenzhofer: none; Herbert Reitsamer: none; Antonio Fea: none; David Yan: none; Moulin-Romsee Marie-Isaline: none; Iqbal (Ike) Ahmed: none 

Abstract Body 

Purpose: To assess the efficacy, safety, and risk factors for failure at 12-months follow-up in a consecutive cohort of glaucoma patients that underwent 63-µm gelatin microstent (Xen63) implantation with Mitomycin C (MMC) versus 45-µm gelatin microstent (Xen45) implantation with MMC, with or without phacoemulsification, on an international scale. Study Design:  This is an investigator-initiated, multicenter, retrospective cohort study. Methods: Consecutive glaucoma patients who underwent Xen63 implantation at 6 surgical centres across 4 countries (Canada, Italy, Austria, Belgium), were retrospectively compared to matched controls who underwent Xen45 implantation, with or without phacoemulsification. Primary outcome was the proportion of eyes at 1 year achieving complete surgical success. Kaplan-Meier survival curves illustrated the cumulative probability of success. Failure was defined as: (1) IOP >17 mmHg or (2) <6 mmHg with 2 lines of vision loss, or (3) <20% reduction from baseline IOP, at 2 consecutive visits, without (complete) or with (qualified) glaucoma medications. Secondary outcomes included surgical success with modified upper IOP thresholds of 14mmHg and 21mmHg, postoperative IOP, medications, interventions, adverse events, and reoperations. Results: 208 eyes (Xen45, n=104; Xen63, n=104) were included. Complete success at 12-months favored Xen63 eyes (64.9% vs. 53.2%; P=0.01), demonstrating significantly lower mean post-operative IOP relative to Xen45 (13.7 ± 6.8mmHg vs. 15.3 ± 6.08mmHg; P=0.002). Mean medication classes at 12 months was lower in Xen63 eyes (0.5 ± 1.0 vs. 1.1 ± 1.5; P=0.01). Adjusted cox proportional hazards model demonstrated a higher risk of failure for Xen45 relative to Xen63 eyes, which was most significant at the strictest IOP threshold of 6-14mmHg (HR 2.0; 95% CI 1.3-3.1). Qualified success also significantly favored the Xen63 group (69.9% vs. 64.4%; P=0.048). 16.3% of Xen63 eyes underwent needling versus 15.4% in the Xen45 group (P>0.05). Choroidals were significantly higher in the Xen63 group in the early postoperative period (23.1% versus 5.8%, P<0.05). A subgroup analysis comparing open versus closed gelatin microstent implantation demonstrated no statistically significant difference in complete success at 1 year between groups. Other adverse events, postoperative interventions, and reoperations rates were comparable. Conclusions: Patients who underwent Xen63 implantation demonstrated higher surgical success rates albeit a higher incidence of choroidals in the early postoperative period. At 1 year, the safety profile was similar between groups with Xen63 having a greater IOP-lowering potency compared to Xen45.