The Effect of Trabeculectomy Approach on Surgically Induced Astigmatism in the Treatment of Open-Angle Glaucoma

Purpose In open-angle glaucoma, trabeculectomy effectively reduces intraocular pressure when medical or laser therapies fail; yet, it typically introduces astigmatism. We conducted a retrospective observational study comparing surgically induced astigmatism (SIA) across three trabeculectomy methods (limbal-based and fornix-based with or without partial-thickness limbal corneal incision) by three surgeons at the University of Iowa Health Care. Methods A chart review was conducted for patients who underwent trabeculectomy for open-angle glaucoma at the University of Iowa Health Care between January 2018 and August 2023. Exclusion criteria included combined phacotrabeculectomy, retinal/corneal comorbidities, concurrent ocular surgeries, and patients under 18 years of age. Pre- and post-operative refractions within two years of surgery were used to calculate SIA. One-tailed analysis of variance (ANOVA), Tukey's Honest Significant Difference test, and chi-square test of independence were performed to compare the surgical approach on SIA and change in the axis of astigmatism. Results The final sample included 87 patients with a mean age of 73.1±11.7 years; 59.8% of patients were women. Twenty-five procedures had a limbus-based approach by Surgeon 1, 23 fornix-based by Surgeon 1, 18 fornix-based by Surgeon 2, and 21 fornix-based by Surgeon 3. While mean SIA ranged from +0.913±0.617 diopters to +1.35±1.47 diopters, there was no significant difference between surgical approaches (p=0.409). Change in axis (p=0.451) or direction of change towards with-the-rule or against-the-rule (p=0.144) did not differ between the surgical approaches. Conclusion This study compared SIA after three trabeculectomy approaches in a single institution. Within our sample, surgical approach was not associated with SIA.