Short-Term Changes in Peripapillary RNFL and Disc-Fovea Angle After Horizontal Rectus Muscle Surgery in Comitant Strabismus

Abstract

Purpose To investigate short-term changes in peripapillary retinal nerve fiber layer (pRNFL) thickness and disc-fovea angle (DFA) after horizontal rectus muscle surgery in patients with comitant strabismus. Patients and Methods This retrospective cohort study included 73 eyes of 73 patients with comitant strabismus who underwent horizontal rectus muscle surgery. Patients were divided according to the number of horizontal rectus muscles operated on in the analyzed eye: Group 1, in which the analyzed eye underwent one-horizontal-rectus-muscle surgery, and Group 2, in which the analyzed eye underwent two-horizontal-rectus-muscle surgery. Optical coherence tomography (OCT) was performed preoperatively, on postoperative day 1, and at postoperative week 2. Global and sectoral pRNFL parameters and the absolute DFA (|DFA|) were analyzed. Results Baseline demographic, refractive, pRNFL, and |DFA| parameters were comparable between the two groups. In Group 1, several pRNFL parameters showed significant early postoperative changes on postoperative day 1, mainly involving G, PMB, T, TI, and NI, and most values returned toward baseline by postoperative week 2. In Group 2, pRNFL changes were more limited, with only TI showing a significant change on postoperative day 1, whereas |DFA| remained significantly different from baseline at postoperative week 2. Between-group comparisons showed greater day 1 changes in G, N, and NI in Group 1, while only the change in |DFA| remained significantly different between groups at week 2. Conclusion Horizontal rectus muscle surgery was associated with mild, transient, and region-specific changes in the pRNFL in patients with comitant strabismus. One-horizontal-muscle surgery was associated with broader early postoperative fluctuations, whereas surgery involving two horizontal muscles was more closely associated with persistent short-term DFA changes.