Refractive and visual changes in the fellow eye after unilateral refractive surgery in patients with anisometropia

This study aimed to investigate the changes in visual acuity and refractive status of the fellow eye after unilateral refractive surgery in patients with anisometropia and to analyze their correlation with factors such as age, degree of anisometropia, and type of ametropia.

A retrospective analysis was conducted on 43 patients with anisometropia who underwent unilateral refractive surgery at the Quzhou People's Hospital, Zhejiang Province, from January 2023 to June 2025. All patients underwent femtosecond laser small incision lenticule extraction (SMILE) or femtosecond laser-assisted excimer laser in situ keratomileusis (FS-LASIK) on the eye with worse uncorrected visual acuity. Follow-up examinations of both eyes were performed preoperatively and at 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively, assessing the uncorrected distance visual acuity and spherical equivalent (SE) of the fellow eye. Repeated-measures analysis of variance (ANOVA) was used to compare changes in the logarithm of the minimum angle of resolution (logMAR) visual acuity and SE of the fellow eye at different time points, and correlations with age, surgical eye SE, and preoperative anisometropia magnitude were analyzed.

The preoperative SE of the operated eye was -2.95 ± 1.84 D, and that of the fellow eye was (-0.25 ± 0.46) D, with a binocular anisometropia difference of 2.71 ± 1.69 D. Within 6 months postoperatively, the refraction of the operated eye remained stable (time main effect p = 0.263), recovering from a preoperative SE of -3.006 D to 0.038 D by 1 day postoperatively, with no significant differences between any postoperative time points (all p = 1.000). The logMAR visual acuity of the operated eye improved from 0.701 preoperatively to 0.017 at 1 day postoperatively and continued to optimize to -0.062 by 3 months postoperatively (superior to standard vision), with no significant fluctuations observed between postoperative time points (p = 0.340). In contrast, the refraction of the fellow eye showed significant changes over time (p = 0.050), with a transient myopic shift at 1 week postoperatively (-0.573 D), which recovered to -0.134 D by 6 months postoperatively, showing no significant difference from preoperative values (p = 1.000). The logMAR visual acuity of the fellow eye remained stable at all time points (p = 0.223), consistently remaining near zero. Age, gender, and other covariates had no significant effect on the change trends of either eye (all p > 0.05).

In patients with anisometropia undergoing unilateral refractive surgery, the fellow eye may experience transient, reversible refractive fluctuations in the early postoperative period, most pronounced at 1 week postoperatively. However, logMAR visual acuity remains stable, indicating the good safety of this surgical approach. Clinicians need not intervene excessively or perform prophylactic bilateral surgery out of concern for visual acuity decline in the fellow eye.