Objective To investigate the effect of varying degree lenticule offset in small incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism,and to evaluate the safety,efficacy,and predictability of the SMILE.Methods In this prospective cohort study,229 eyes of 115 patients underwent SMILE with VisuMax laser (Carl Zeiss).The mean spherical equivalent (SE) was-2.25 to-9.75 D,with an average of-5.13±2.11 D,astigmatism was 0 to 4.25 D,with an average of 1.12±0.68 D.Based on the degree of lenticule center deviates from the standard center,patients were divided into group A (less than 80 μm),group B (80 to 150 μm) and group C (more than 150 μm).Uncorrected visual acuity (UCVA),aberration and residual astigmatism after surgery were measured.Data were compared using a ANONA,K-WH test and corrected chi-square test.Results There were no intraoperative and postoperative accidents and serious complications,and postoperative UCVA improved markedly.One day,3 months postoperation the differences were statistically significant (x2=50.713,F=19.011,P＜0.01).The differences of residual astigmatism between the 3 groups 1 day and 3 months postoperation were significantly (x2=28.272,34.721,P＜0.01).The anterior corneal surface coma and spherical aberration postoperative were increased.Group C had the most significant increase in coma (C7,C8),followed by group B,group A minimum,the differences between the 3 groups were significant (x2=51.533,49.804,P＜0.01).While the differences in the changes in spherical aberrations between the groups were not statistically significant (x2=2.794,P＞ 0.05).Conclusion Attention to the accuracy of lens positioning can improve the effectiveness of surgery,and reduce the occurrence of postoperative astigmatism and coma.