Outcomes of Ab Interno 63 µm vs. 45 µm XEN^® Gel Stent in Open-Angle Glaucoma: A Five-Year Follow-Up Study

Background/Objectives: To compare the five-year efficacy and safety of the 63 µm (XEN63) vs. 45 µm (XEN45) XEN^® Gel Stent in patients with open-angle glaucoma (OAG). Methods: This retrospective matched (1:1) cohort study included adults with OAG who underwent standalone ab interno implantation of the XEN63 or the XEN45 between 2014 and 2021 at a tertiary referral center in Belgium. The primary outcome was IOP at five years. The secondary outcomes included surgical success, topical medication use, postoperative hypotony, complications and interventions. Results: Thirty eyes of 30 patients (15 XEN63 and 15 XEN45) were analyzed. The baseline characteristics were comparable. At five years, the mean IOP did not differ between the XEN63 and the XEN45 (11.5 vs. 11.0 mmHg; p = 0.54). The XEN63 demonstrated higher complete success rates than the XEN45 for both the IOP < 18 mmHg (10 vs. four eyes; p = 0.016) and <15 mmHg criteria (10 vs. three eyes; p = 0.003). The topical medication use was low and comparable (0.6 vs. 0.9 medications; p = 0.57). The numerical (13 vs. five eyes; p = 0.008) and symptomatic (six vs. two eyes; p = 0.2) hypotony were more frequent after the XEN63 implantation. The two eyes with XEN63 and none with XEN45 experienced clinically significant hypotony. The needling procedures and secondary glaucoma surgeries were more frequent after the XEN45. Conclusions: The XEN63 implantation was associated with higher long-term success rates and also with a higher incidence of early postoperative hypotony. These findings indicate a trade-off between efficacy and safety and suggest that careful patient selection and postoperative management are essential when considering larger lumen subconjunctival drainage devices.