Outcomes of higher-order aberration correction in relation to optical zone size after Phorcides-planned laser in situ keratomileusis in Indian Eyes

PURPOSE: To evaluate the influence of additional ablation (Abl-max) on higher-order aberrations (HOAs), particularly corneal coma, following Phorcides-planned topography-guided laser in situ keratomileusis (LASIK) in an Indian population. METHODS: We analyzed 161 eyes of 83 patients undergoing Phorcides-planned topography-guided LASIK between June 2022 and June 2023. Assessments at baseline and 1, 3, and 6 months included distance visual acuity, manifest refraction, Pentacam tomography, and iTrace aberrometry. Abl-Max was stratified into quartiles (Q1-4) and deciles (Q1-10). The primary outcomes were total HOAs and corneal coma (KCm) at 6 months. Logistic, linear, and decision tree regression models identified predictors of low coma (lowest quartile of KCm6 ≤ 0.037μ). RESULTS: Q1 of Abl-max eyes had higher baseline myopia (-4.36 ± 1.62D vs. -2.76 ± 1.79D), and fewer were treated with 6.5 mm Optic Zone (OZ) (31.2% vs. 67.6%) compared to Q4 (both P < 0.001). At 6 months, KCm6 was higher in Q1 (0.11 ± 0.10 vs. 0.07 ± 0.06 μm in Q4, P = 0.015). The mean postoperative binocular uncorrected vision was 20/17 in both quartiles. Logistic regression showed that lower myopia (OR 1.51, 95% CI 1.21-1.92; P = 0.0004) and 6.5 mm OZ (OR 4.24, 95% CI 0.92-20.38; P = 0.066) predicted low coma. A decision tree model achieved AUROC 0.77, with the lowest coma in eyes with mild-moderate myopia (-2D to -3D) and 6.5 mm OZ. CONCLUSION: Phorcides-planned LASIK permits safe deeper ablations with excellent vision, but coma induction persists, especially in higher myopes (>-4D) with 6.0 mm OZ. Larger OZs (6.5 mm) may optimize coma outcomes where residual stromal thickness permits.