Intermediate Outcomes of the Novel 63-μm Gelatin Microstent versus the Conventional 45-μm Gelatin Microstent

Abstract

Purpose: To determine intermediate intraocular pressure (IOP)-lowering and adverse event profile of the 63-μm gelatin microstent (Xen63) with mitomycin C (MMC) compared with the 45-μm gelatin microstent (Xen45) with MMC.

Design: Single center, consecutive, retrospective cohort study.

Participants: Eighty-four glaucomatous eyes (42 63-μm gelatin microstent and 42 45-μm gelatin microstent) with or without previous subconjunctival glaucoma surgery.

Methods: Consecutive eyes that underwent 63-μm gelatin microstent implantation with MMC from February 2020 to June 2021 were compared with eyes that underwent 45-μm gelatin microstent implantation with MMC. Standalone and combined cases with phacoemulsification were included.

Main outcome measures: Primary outcome was the hazard ratio of failure of 45-μm gelatin microstent vs. 63-μm gelatin microstent eyes at 12 months, with failure defined as 2 consecutive IOPs, (1) >17 mmHg, (2) <6 mmHg with 2 lines of vision loss, or (3) <20% reduction from baseline IOP, without (complete) or with (qualified) glaucoma medications. Secondary outcomes included IOP thresholds of 14 mmHg and 21 mmHg, postoperative IOP, medications, adverse events, interventions, and reoperations.

Results: The complete success rate was higher in the 63-μm gelatin microstent group (59.5% vs. 28.6%, P = 0.009) at the primary IOP threshold of 6 to 17 mmHg but did not differ significantly for qualified success (66.7% vs. 45.2%, P = 0.08). The crude hazard ratio of failure of 45-μm gelatin microstent relative to 63-μm gelatin microstent was 2.28 (95% confidence interval [CI], 1.21-4.32), and the adjusted hazard ratio was 7.90 (95% CI, 2.12-29.43). 63-μm gelatin microstent eyes had significantly lower mean IOP (12.7 ± 4.8 vs. 15.5 ± 5.1 mmHg, P = 0.001) and fewer medication classes (0.6 ± 1.1 vs. 1.7 ± 1.6 medications, P = 0.0005), with the degree of reduction in IOP and medication count being significantly greater in 63-μm gelatin microstent eyes. There were 28 and 21 distinct interventions in 63-μm gelatin microstent and 45-μm gelatin microstent eyes respectively, with 11.9% of eyes undergoing needling in each group. There were 34 and 19 distinct adverse events, in 63-μm gelatin microstent and 45-μm gelatin microstent eyes, respectively, most of which were early and transient. Nine Xen63 eyes (21.4%) and 6 45-μm gelatin microstent eyes (14.3%) underwent reoperation.

Conclusions: 63-μm gelatin microstent resulted in higher surgical success rates and fewer medications compared with 45-μm gelatin microstent. This was tempered by more postoperative interventions and adverse events, although most were transient.

Financial disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Gelatin microstent; Glaucoma surgery; Subconjunctival filtering.