Outcomes of sequential bilateral XEN®45 implantation: evidence for a fellow-eye effect influencing early management

To evaluate inter-eye differences in efficacy, safety, and prognostic indicators between the first-operated and fellow eyes in patients undergoing bilateral XEN®45 gel stent implantation, with particular focus on early intraocular pressure control, intervention timing, and the influence of first-eye outcomes on the second eye. A retrospective cohort study. This single-center retrospective study analyzed 34 eyes of 17 consecutive patients who underwent bilateral XEN®45 implantation. We compared the baseline data and postoperative outcomes of the first-operated eyes vs. the fellow eyes. The primary outcome in the study was the clinical success rate (complete: IOP 6–18 mmHg without medications; qualified: IOP 6–18 mmHg with/without medications). The baseline characteristics of the first-operated and fellow eyes were comparable, with no significant differences in intraocular pressure (22.7 ± 9.2 mmHg vs. 22.4 ± 9.6 mmHg, P = 0.904) or the number of IOP-lowering medications used (3.6 ± 0.9 vs. 3.3 ± 0.8, P = 0.056). The fellow eyes showed numerically higher IOP but the difference was not statistically significant at 3 months (17.2 ± 7.1 vs. 13.9 ± 3.6 mmHg, P = 0.101). The fellow eyes required earlier first needling interventions (2.7 ± 1.8 vs. 3.6 ± 4.4 months, P = 0.041) and showed a numerically higher, though non-significant, surgical bleb revision rate (41.1% vs. 11.7%, P = 0.125). At final follow-up, complete (73.5% vs. 70.6%) and qualified (85.3% vs. 82.4%) success rates were statistically equivalent. Success of the fellow eye was significantly associated with success of the first-operated eye (P = 0.047, OR = 21.5). While bilateral XEN®45 implantation achieves comparable final success rates in both eyes, fellow eyes show signs of earlier fibrosis and intervention needs, highlighting a “fellow-eye effect” and the importance of individualized management for the second eye.