Theoretical analysis of wavefront aberration caused by treatment decentration and transition zone after custom myopic laser refractive surgery

PURPOSE: To analyze the induced wavefront aberrations caused by treatment decentration and transition zone after custom myopic laser refractive surgery. SETTING: Refractive Surgery Center, Tianjin Eye Hospital & Eye Institute, Tianjin Medical University, Tianjin, China. DESIGN: Cohort study. METHODS: Wavefront aberration data from potential refractive surgery candidates were used. Based on the preoperative wavefront aberrations, the custom ablation profile was computed. Then, the influence of treatment decentration and especially that of the transition zone on induced wavefront aberrations was studied. The impact of angle mismatch on induced aberrations was analyzed. RESULTS: Data from 117 eyes (77 patients) were analyzed. The transition zone played a significant role in the influence of decentration on the induced aberrations in refractive surgery. Induced coma and spherical aberration increased rapidly as the lateral translation increased, and coma was significantly larger than other Zernike aberration terms. The induced aberrations from decentration with oblique incidence in the laser ablation profile were less than in the actual laser ablation process for slight subclinical decentration. The induced aberrations were not closely related to the subclinical unmatched angle from eye cyclotorsion. The induced aberrations from lateral translation were correlated with the position vector. The transition zone was designed to smooth the transition from the optical zone to the untreated cornea, and it mainly dominated induced coma and spherical aberration. CONCLUSION: To achieve the best postoperative visual performance, the effect of the transition zone in refractive surgery should be taken into account, especially for scotopic pupils.