Stability of anterior segments in patients with moderate and high myopia one year after SMILE
Authors: Lei Cheng , Yuhao Zhu , Ran Zhu , Chao Song 
Published: July 2022

Abstract
Background: SMILE is one of the most leading-edge corneal refractive surgery.In our study, we aim to investigate the stability of anterior segments in patients with moderate and high myopia one year after SMILE. Methods: 30 eyes of 15 patients who underwent SMILE surgery from July 2020 to January 2021 were collected, including 7 males and 8 females, aged from 20 to 37 years (average 27.20 ± 5.40 years old). Pentacam AXL anterior segment analyzer was performed before operation, 1 month and 1 year after operation to measure the relevant data of anterior segments, including the elevation of posterior corneal surface, Q value of anterior and posterior corneal surface (8mm), curvature of anterior and posterior corneal surface, central anterior chamber depth (ACD), anterior chamber volume and peripheral anterior chamber angle (ACA). Results: all the operations were successful without complications. There were significant differences in preoperative and postoperative equivalent spherical lens, average curvature(km) of anterior and posterior corneal surface , posterior elevation at the thinnest corneal point and Q value of anterior and posterior corneal surface (F = 755.055, P < 0.05; F = 700.001, P < 0.05; F = 3.494, P = 0.037, P < 0.05; F = 8.374, P = 0.001; F = 393.012, P < 0.05; F = 28.179, P < 0.05). There was no significant difference in posterior elevation at the apex corneal point(F = 0.301, P = 0.693＞0.05); Among them, there was significant difference in equivalent spherical lens,posterior elevation at the thinnest corneal point , Q value of anterior and posterior corneal surface between before operation and two points of time after operation (P < 0.05), and there was no significant difference between the two points of time after operation (P = 0.051,1.000,0.805,0.531 > 0.05); The pairwise comparison between the three groups were statistically significant in the mean corneal anterior surface curvature (P < 0.05); There was significant difference in the mean corneal posterior surface curvature between preoperative and 1 month after operation (P = 0.047 < 0.05), but there was no significant difference between preoperative and 1 year after operation, between 1 month after operation and 1 year after operation (P=0.117,1.000>0.05);The pairwise comparison among three groups were not statistically significant (P = 1.000 > 0.05); There were significant differences in anterior chamber depth (ACD), anterior chamber volume (ACV) and anterior chamber angle (ACA) before operation and 1 month 1 year after operation (F = 52.649,95.697,10.520, P < 0.05); There was significant difference in ACD and ACV between before operation and two times after operation (P < 0.05); There was no significant difference in ACA between before operation and 1 month after operation (P = 0.297 > 0.05), but there was significant difference in ACA between before operation and 1 year after operation, 1 month after operation and 1 year after operation (P = 0.001,0.035 < 0.05). Conclusions: the corneal surface morphology before and after SMILE will change in the early stage, but it will gradually stabilize in the medium and long term, and the anterior chamber parameters change, which needs more attention.