1 Department of Ophthalmology, Gansu Provincial People's Hospital, Lanzhou 730000, China 2 The Gansu University of Traditional Chinese Medicine, Lanzhou 730000, China
Abstract： Objective: To study the changes in corneal thickness and relevant factors after small incision lenticule extraction (SMILE). Methods: This was a retrospective case series study. A total of 120 patients (240 eyes) with low to high myopia who had undergone SMILE surgery and completed a 1-year follow-up were enrolled from the Optometry Center of Gansu Provincial People's Hospital. Corneal thickness of the apex and concentric circles of the diameter at 2 mm and 6 mm locations were examined by Pentacam at 1 day, 1 week, 1 month, 3 months, 6 months and 1 year after surgery. The changes in corneal thickness (△CT) in the same area at the adjacent time points and the different areas at the same time were compared. Paired samples t-test was used for intra-group comparison, repeated measurement of variance was used for intergroup comparison, and LSD-t test was used for pairwise comparison between groups. Results: In the three groups, the △CT of the different areas all increased from 1 day to 1 week after surgery, and the results were statistically significant (P<0.05). From 1 week to 1 month, corneal thickness became thinner; from 1 month to 3 months after the operation, all the corneal areas had thickened by different degrees (P<0.05). From 3 months to 1 year, the △CT of the different areas were positive and the growth of corneal thickness decreased slowly, and the difference was not statistically significant. The thickness from the center to the periphery decreased from 1 month to 1 year after surgery, and the thickening in the center was more obvious than that in the periphery. There were statistically significant differences at the apex and concentric circles of the diameter at 2 mm among the three groups (P<0.05), while there were no statistically significant differences at 6 mm circles. The changes in corneal thickness had a positive correlation with spherical equivalence (SE) and ablation depth (AD) (r=0.73, P<0.001; r=0.38, P<0.001), but a negative correlation with residual bed thickness (RBT)(r=-0.27, P=0.01). There was a positive correlation between IOP (r=0.69, P<0.001) and thickening of the cornea in the high myopia group. Conclusions: Corneal thickness gradually increases after SMILE and is basically stable after 3 months. Central thickening is more obvious than peripheral thickening. The higher the degree of myopia, the more obvious the thickening is.
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