The aim of this study was to investigate the early changes of posterior corneal elevation and possible influencing factors in moderate and high myopia after small incision lenticule extraction (SMILE).

This was a retrospective study. From Sep. 2017 to May 2018, case data of 63 patients (110 eyes) with moderate and high myopia who received SMILE in The First Affiliated Hospital of Guangxi Medical University were collected; parameters obtained by Pentacam Scheimpflug system of preoperation and postoperative 1 d, 1 week, 1 month and 3 months were selected, including the posterior corneal elevation at corneal apex and 45°, 135°, 225°, 315° points of two zones (centered on corneal apex 2 mm, 4 mm diameter), the mean of the 9 points above was taken as the central posterior corneal elevation. One-way repeated measures ANOVA was used to analysis the posterior corneal elevation at corneal apex and central corneal of different time pints, and Pearson product moment coefficient was used to analysis the correlation of the change of posterior corneal elevation at corneal apex and central corneal and the age of patients, preoperative spherical equivalent, central corneal thickness, corneal cutting depth, residual corneal thickness or corneal cutting ratio.

The posterior corneal elevation at corneal apex and central corneal declined within postoperative 1 month and turn back after postoperation for 1 month. After preoperation for 1 day, 1 week, 1 month and 3 months, the posterior corneal elevation at corneal apex were (0.52±2.46) mm, (0.39±2.21) mm, (0.33±2.33) mm, (-0.06±2.18) mm and (0.00±2.72) mm, respectively; the posterior corneal elevation at central corneal were (1.18±0.90) mm, (1.16±0.76) mm, (1.06±0.76) mm, (1.04±0.74) mm, (1.09±0.89) mm at postoperative for 1 day, 1 week, 1 month and 3 months, respectively; the difference was no significant among them (F=1.24, 0.62; P>0.05). At postoperative 1 day, 1 week, 1 and 3 months, the average changes of posterior corneal elevation at corneal apex (-0.13±1.43) mm, (-0.19±1.74) mm, (-0.58±1.65) mm, (-0.52±1.96) mm, respectively; and the average changes of posterior corneal elevation at central corneal (-0.02±0.68) mm, (-0.12±0.74) mm, (-0.14±0.78) mm, (-0.09±0.95) mm, respectively; the difference was also no significant among them (F=1.98, 0.47; P>0.05). There was no correlation between the change of posterior corneal elevation at corneal apex and central corneal and the age of patients, preoperative spherical equivalent, central corneal thickness, corneal cutting depth, residual corneal thickness or corneal cutting ratio at each time point (P>0.05).

There was no obvious change in the posterior corneal elevation which recovered in the early postoperative period. SMILE has little effect on the posterior corneal morphology, which is safe and stable for patients with moderate and high myopia.