Comparison of the Distribution of Lenticule Decentration Following SMILE by Subjective Patient Fixation or Triple Marking Centration.

PURPOSE: To investigate lenticule decentration following small incision lenticule extraction (SMILE) via the subjective patient fixation method or triple marking centration method and compare inductions of corneal higher order aberrations (HOAs) between the two methods.

METHODS: This study analyzed decentration values obtained from the Keratron Scout (Optikon, Rome, Italy) tangential topography difference map of 110 eyes (110 patients) undergoing SMILE with the subjective patient fixation method (n = 55) or triple marking centration method (n = 55). Root mean square values of total HOAs, 3rd order coma aberration, and 4th order spherical aberration, as well as individual coefficients for vertical and horizontal coma, were measured preoperatively and 3 months postoperatively. Relationships between the magnitudes of decentration and induced corneal HOAs were assessed.

RESULTS: There were significant differences in horizontal decentered displacement (P = .048), vertical decentered displacement (P = .002), and total decentered displacement (P = .001) between the two groups. Total HOAs, coma, vertical coma, and spherical aberration significantly increased in the subjective patient fixation method (all P < .001), whereas total HOAs (P = .002) and vertical coma (P = .005) increased in the triple marking centration method. Induction of total HOAs (mean values: 0.13 vs 0.07; P = .026), coma (0.09 vs 0.03; P = .032), and spherical aberration (0.08 vs 0.02; P = .013) was significantly greater in the subjective patient fixation method than in the triple marking centration method. Association between the total decentered displacement and induced vertical coma (P = .006) or induced spherical aberration (P = .018) was significant in the subjective patient fixation method.

CONCLUSIONS: SMILE with the triple marking centration method can yield improved treatment centration and smaller induction of total HOAs, coma, and spherical aberrations. [J Refract Surg. 2018;34(7):446-452.].