Comparison of visual outcomes following ray-tracing-guided femtosecond laser-assisted in situ keratomileusis with different optical zone sizes

To evaluate the impact of different optical zone (OZ) size on clinical outcomes following ray-tracing-guided femtosecond laser-assisted in situ keratomileusis (FS-LASIK). A total of 126 eyes of 63 patients were stratified by intended OZ size: 6.5- group (6.0 - 6.5 mm) and 6.5+ group (6.6 - 7.0 mm). Group assignment was non-randomized and based on the surgeon’s preoperative clinical judgment. Standardized preoperative and 3-month postoperative evaluations included uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, mean keratometry, intended/achieved maximum ablation depth, central corneal thickness, residual stromal bed thickness, percent tissue altered, low-mesopic pupil diameter, 6-mm total ocular wavefront aberrations, and the Quality of Vision (QoV) questionnaire. Both groups achieved excellent refractive accuracy and stability. No significant differences were observed in spherical equivalent, refractive or surgically induced astigmatism, difference vector, mean keratometry, central corneal thickness, maximum ablation depth, or QoV scores (all p > 0.05). At 3 months, 80% of the 6.5- group and 76% of the 6.5+ group achieved UDVA of 20/16 or better ( p = 0.797). The 6.5+ group showed significantly lower root mean square (RMS) values for total higher-order-aberrations (HOAs, p = 0.005) and coma-RMS ( p = 0.013). For the signed Zernike coefficients of spherical aberration ( p = 0.016) and vertical coma ( p = 0.023), between-group differences reflected directional shifts rather than reductions in aberration magnitude. In this retrospective, non-randomized cohort, larger intended OZs were associated with lower postoperative HOAs-RMS and coma-RMS within a fixed 6-mm aperture, without compromising visual acuity, refractive accuracy, or safety. Given the methodological limitations of this retrospective design, this observational association should not be regarded as definitive causal evidence; prospective randomized studies are warranted to confirm these observations. Chinese Clinical Trial Registry (ChiCTR2500107271), retrospectively registered on August 7th, 2025.