Comparison of Corneal Deformation Parameters After SMILE, LASEK, and Femtosecond Laser-Assisted LASIK

PURPOSE: To investigate the differences in corneal deformation parameters after femtosecond laser small incision lenticule extraction (SMILE), laser-assisted subepithelial keratomileusis (LASEK), and femtosecond laser-assisted LASIK (FS-LASIK). METHODS: In this retrospective study, 17 eyes of 17 patients after SMILE, 18 eyes of 18 patients after LASEK, and 17 eyes of 17 patients after FS-LASIK were included. Corneal deformation parameters were measured with the CorVis ST tonometer (Oculus Optikgerate GmbH, Wetzlar, Germany) 3 months postoperatively. RESULTS: The mean value of deformation amplitude of the FS-LASIK group was significantly higher than that of the LASEK group (P =.022). The mean value of applanation time (applanation 1) of the LASEK group was significantly higher than that of the FS-LASIK group (P =.038). No significant difference was detected in the mean values of deformation amplitude and applanation time (applanation 1) (P >.05) between the LASEK and SMILE groups or between the SMILE and FS-LASIK groups. Multiple linear regression model analysis revealed that after adjustment for age and preoperative central corneal thickness and manifest refraction spherical equivalent, the significance of the difference in the mean values of applanation time (applanation 1) and deformation amplitude between the LASEK and FSLASIK groups were P =.084 and.059, respectively. In all three groups, the values of applanation 1 negatively correlated to those of applanation time (applanation 2) (SMILE: r = -0.577, P =.015; LASEK: r = -0.833, P <.001; FS-LASIK: r = -0.516, P =.034) and deformation amplitude (SMILE: r = -0. 556, P =.021; LASEK: r = -0.877, P <.001; FS-LASIK: r = -0.509, P =.037). CONCLUSIONS: Applanation time (applanation 1) and deformation amplitude (as measured with the CorVis ST tonometer) may be helpful in assessing corneal biomechanical changes after corneal refractive surgery. The relations between these parameters should be discussed in further studies.