Comparison of Surgically Induced Astigmatism After Glaucoma Filtering and Implant Procedures

To compare keratometric surgically induced astigmatism (SIA) at 3 months after trabeculectomy (LEC), EX-PRESS shunt (EXP), PRESERFLO MicroShunt (PSM), and Ahmed glaucoma valve (AGV) with ciliary-sulcus tube insertion using vector analysis, and to assess the directionality of SIA.

Single-center, nonrandomized, retrospective comparative study.

We retrospectively analyzed 100 eyes with glaucoma undergoing LEC (n = 20), EXP (n = 30), PSM (n = 30), or AGV (n = 20) at a single center. Best-corrected visual acuity (BCVA), intraocular pressure (IOP), and keratometric astigmatism were evaluated preoperatively and at 3 months postoperatively. SIA was calculated using the Jaffe vector method. Directional non-uniformity of the SIA axis was assessed using the Rayleigh test after double-angle transformation. Associations between SIA magnitude and postoperative IOP and BCVA were assessed using Spearman's rank correlation. In the LEC group, the association between SIA magnitude and the number of residual scleral-flap sutures was also evaluated.

Preoperative and postoperative corneal astigmatism magnitudes did not differ significantly among the four groups. Arithmetic mean individual SIA magnitudes were 1.17 ± 0.80 D in the LEC group, 0.66 ± 0.44 D in the EXP group, 0.65 ± 0.57 D in the PSM group, and 0.58 ± 0.28 D in the AGV group (overall P = 0.035). SIA magnitude was significantly greater after LEC than after EXP, PSM, and AGV (Holm-adjusted P = 0.031, 0.031, and 0.015, respectively), whereas no significant differences were detected among EXP, PSM, and AGV. Significant directional non-uniformity of the SIA axis was detected only in the LEC group, with a circular mean axis of 19.9° (mean resultant length, 0.487; Rayleigh Z = 4.740, P = 0.007), consistent with a with-the-rule-oriented astigmatic change. No significant correlations were detected between SIA magnitude and postoperative IOP or BCVA in any surgical group. In the LEC group, SIA magnitude was not significantly correlated with the number of residual scleral-flap sutures.

At 3 months, LEC was associated with greater keratometric SIA than EXP, PSM, and AGV. Significant with-the-rule-oriented directional non-uniformity was detected only after LEC.