Clinical Outcomes of Ab Interno Placement versus Ab Externo Placement of XEN45 Gel Stents

Abstract

Purpose: To compare the effectiveness of ab interno versus ab externo placement of XEN45 gel stents in patients with open-angle glaucoma.

Design: Single-center, noncontrolled, retrospective, comparative case series.

Participants: Eighty-nine eyes of 89 patients with open-angle glaucoma who underwent XEN45 gel stent implantation.

Methods: Patients underwent either ab interno (group 1) or ab externo (group 2) placement of a XEN45 stent between 2017 and 2020 by a single surgeon. Outcomes were recorded at each follow-up visit from postoperative day 1 up to 24 months, with median follow-up lengths of 12 months and 8 months for groups 1 and 2, respectively.

Main outcome measures: The primary outcome measure was the surgical success rate at 8 months. Secondary measures were postoperative intraocular pressure (IOP) and medication usage, complication rates, and bleb revision rates.

Results: Success rates at 8 months were 72% in group 1 (n = 29) and 74% in group 2 (n = 60). There was no difference in the median time to failure between groups (P = 0.98). The mean baseline IOPs were 22.8 ± 7.5 on 3.8 ± 0.9 medications in group 1 and 25.3 ± 10.7 on 3.7 ± 1 medications in group 2. At the last follow-up among eyes with surgical success, the mean IOPs were 12.5 ± 3.8 on 2.2 ± 1.4 medications in group 1 and 12.2 ± 2.1 on 1.8 ± 1.3 medications in group 2. The adjusted mean IOPs and numbers of medications used were significantly lower after XEN45 stent implantation at all postoperative time points compared with baseline in both groups (P < 0.05). There were no significant differences in postoperative adjusted mean IOPs or medications used between the groups at any of the follow-up time points. Complication rates and bleb revision rates were comparable between both groups (P > 0.05).

Conclusions: The ab externo approach of XEN45 stent placement demonstrates comparable effectiveness to the ab interno approach in patients with open-angle glaucoma, although this study was underpowered to detect a difference in success rates between groups.

Keywords: Ab externo; Ab interno; Gel stent; Glaucoma surgery; XEN.