AIM: To compare the effect of small-incision lenticule extraction(SMILE)with different corneal cap thicknesses on postoperative astigmatism and short-term visual quality of patients with myopic astigmatism.

METHODS: A total of 54 patients(108 eyes)with myopic astigmatism who underwent SMILE from June 2020 to June 2022 in our hospital were selected for the prospective controlled study, and patients were randomly assigned into two groups, with 27 cases(54 eyes)each. The corneal cap thickness design was 110 μm for the group A and 120 μm for the group B, while other operation parameters were consistent. Additionally, the uncorrected visual acuity(UCVA), spherical equivalent(SE), stiffness parameter A1(SP-A1), visual quality and vector parameters at baseline, 1 d,1 wk and 1 mo after surgery were compared between two groups.

RESULTS: There was a statistically significant difference in UCVA, SE, and SP-A1 between the two groups at various time points before and after surgery(all P<0.05), and UCVA in the group A was better than that in the group B at 1 d after surgery(P<0.05). There was no statistically significant difference in the results of astigmatism vector analysis between the two groups of patients(both P>0.05). The objective scattering index(OSI)of the group A was lower than that of the group B, while Strehl ratio(SR)of the group A was higher than that of the group B at 1 d after surgery(both P<0.05). There was no significant difference in modulation transfer function cutoff frequency(MTF cut off), contrast vision, visual symptoms and overall satisfaction, postoperative complications between the two groups(all P>0.05).

CONCLUSION: SMILE procedures with both 110 μm and 120 μm corneal cap thicknesses are safe and effective in correcting myopic astigmatism without affecting postoperative SE, astigmatism, SP-A1 or contrast visual acuity. Whereas 110 μm corneal cap thickness results in faster early postoperative visual recovery and better early visual quality than 120 μm.