A Clinical Study Of Ablation Center After Small Incision Lenticule Extraction

Purpose:To compare the location of ablation center after small incision lenticule extraction (SMILE), entrance pupil center(EPC) and corneal vertex(CV).Methods:105eyes of54patients were treated with SMILE. The corneal topography was acquired before and3months after SMILE with Orbscan II anterior segment analyzer. Two methods were taken to determine the ablation center with information from the topography. The impact of kappa angle on ablation center was evaluated, as well as the correlation between decentration and the induced higher order aberrations (HOA).Results:The mean decentration from CV was0.219±0.130mm for method1and0.261±0.167mm for method2, whereas the distribution of the ablation centers demonstrated a superior and nasalization pattern. The mean distance between ablation center and EPC was0.245±0.141mm for method1and0.261±0.161mm for method2, with ablation center nasalized relative to EPC. The centration in70%(method1) and67%(method2) cases followed the preoperative pattern of angle kappa. The angle kappa magnitude was found no correlation with the decentration from CV, while a positive correlation(r=0.303, p=0.002) with the decentration(method1) from EPC. The total HOA, spherical aberration, vertical coma, horizontal coma, and coma had significantly increased postoperatively. Decentration from CV was associated with horizontal coma(method1:p=0.241, p=0.015; method2:p=0.457, p=0.000) and coma (method1:β=0.253, p=0.007; method2:p=0.335, p=0.000) in a multiple linear regression model.Conclusion:The centration in SMILE was effective with ablation center closer to CV. The distribution of most centration followed the preoperative pattern of angle kappa, while decentration has no correlation with angle kappa magnitude. Visual quality would be improved with more centered ablation.