Abstract: Objective  To investigate the effects of tissue removal thickness on corneal biomechanics after small incision femtosecond laser corneal stromal lens extraction(SMILE) and femtosecond laser corneal stromal lens extraction(FLEx) in ametropic patients. 
Methods  A total of 240 cases of refractive lensectomy due to refractive errors. According to the operation method, the patients were divided into observation group and control group. The observation group was treated with SMILE, while the control group was treated with FLEx. The changes of visual acuity, corneal height and corneal biomechanical parameters were observed after operation. 
Results  There were significant differences in UDVA and BCVA between two groups at 1 day, 1 week, 1 month, and 1 year(P＜0.01), and interactions between different operations and time(P＜0.01). However, there was no difference between the groups at each time point(P＞0.05); after 3 months, the control group and the observation group measured the cornea. The height of each region was changed, and there was no significant difference between the apex and the 2 mm ring. However, the difference between two groups was significant at 4 mm and 6 mm rings(P＜0.05). There were significant differences in △CH and △CRF between two groups at 1 week, 1 month, and 3 months after operation(P＜0.01), and interactions between different operations and time(P＜0.01), but two groups. There was no difference at the time point(P＞0.05).
Conclusion  The visual acuity of patients after SMILE and FLEx can be improved. However, in terms of corneal biomechanical changes, SMILE has less impact on corneal biomechanics, and corneal biomechanical stability is better after surgery. 

Key words: refractive errors, orneal surgery, laser, biomechanics