Centration of myopic refractive ablation: should we center treatment on the pupil or the visual axis?

The purpose of this study is to compare pupil versus corneal vertex-centered ablation for myopic laser refractive surgery. This study is a retrospective case series of right eyes of consecutive myopic patients undergoing either photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) with pupil or corneal vertex-centered ablation from January 2018 to April 2018. Overall 258 eyes of 258 patients were included. Of the 104 that underwent LASIK, 52 were treated centered on the corneal vertex (50%), and of the 154 that underwent PRK, 77 were treated centered on the corneal vertex (50%). There were no significant differences in baseline age, gender, spherical equivalence, sphere, cylinder, or angle kappa between both groups in either LASIK or PRK. There were no significant differences between the corneal vertex-centered and pupil-centered groups in terms of efficacy index (LASIK: 1.02 ± 0.14 vs 1.01 ± 0.13, p = 0.86; PRK: 1.00 ± 0.13 vs 0.99 ± 0.15, p = 0.61), safety index (LASIK: 1.02 ± 0.12 vs 1.01 ± 0.13, p = 0.70; PRK:1.02 ± 0.12 vs 1.02 ± 0.09, p = 0.97), and residual astigmatism (LASIK: 0.26 ± 0.25 vs 0.23 ± 0.28, p = 0.65; PRK:0.37 ± 0.41 vs 0.39 ± 0.31, p = 0.78). In mixed effect models, there were no significant differences between the corneal vertex-centered and pupil-centered groups when accounting for angle kappa (p > 0.05). Patients with large angle kappa (> 300 μm) eyes yielded similar results (p > 0.05). For conclusion, in myopic refractive surgery, performing ablation centered on the corneal vertex or on the pupil leads to similar outcomes regardless of the amount of angle kappa.