Comparison of Keratometric Changes After Ab Interno Gel Stent Implantation, Glaucoma Drainage Devices and Trabeculectomy.

Purpose: To compare postoperative keratometric changes and surgically induced astigmatism (SIA) after Ab Interno Gel Stent Implantation (XEN), glaucoma drainage device (GDD), and trabeculectomy (TRAB). GDDs included Ahmed glaucoma valve (AGV) and Baerveldt glaucoma implant (BGI).

Design: Prospective, interventional, longitudinal study.

Participants and methods: Fifty-one eyes with glaucoma undergoing glaucoma filtering surgery were recruited between November 2020 and May 2023. The groups consisted of 19 XEN implants (37%), 21 GDDs (41%) (2 AGVs, 19 BGIs), and 11 trabeculectomies (22%). Primary outcomes were SIA at 12 months postoperatively, measured by Pentacam (Scheimpflug imaging) and OPD-scan (topography). The arithmetic mean of SIA (M-SIA) and the centroid of SIA (C-SIA) were determined using vector analysis. Secondary outcomes included BCVA, IOP, number of meds, and complications.

Results: At 12 months, C-SIA measured by tomography was similar across all groups (0.3 ± 1.0 D for XENs and GDDs and 0.4 ± 1.0 D for TRAB). Topography measurements demonstrated a C-SIA of 0.2 ± 0.9 D for XENs, 0.1 ± 0.9 D for GDD, and 0.6 ± 1.7 D for TRAB. TRAB showed a trend towards a higher proportion of eyes with >1D of astigmatism (73%) compared to the XEN (27%) and GDD groups (48%, p = 0.159).

Conclusion: SIA was similar across groups when measured by tomography, while topography measurements indicated a trend towards more SIA with TRAB. Mean cylinder values at 12 months were higher in the TRAB group.