AIM: To compare the impact of different thickness of corneal cap design on small incision lenticule extraction(SMILE)operation.

METHODS: Forty-six cases of myopia patients(92 eyes)intends to SMILE operation in our hospital were collected, and were randomly divided into 2 groups: corneal cap thickness design for 110μm in group A and 120μm in group B. Other operation parameters designs were consistent. All patients were surgeried by the same surgeon. The incidence of opaque bubble layer(OBL), the ratio of difficult separation of lens, uncorrected visual acuity(UCVA)of each time points, and spherical equivalent(SE)were compared.

RESULTS: Intraoperative OBL incidence rate of 110μm group was higher than that of 120μm group with significant difference between the two group(P<0.05). the ratio of difficult separation of lens was significantly different between the two groups: 110μm group was higher than in 120μm group(P<0.05). The UCVA in the 120μm group was better than that in the 110μm group at postoperative 1 and 7d. But with the passage of time, postoperative 1, 3, and 6mo of UCVA of 2 groups was similar, showed no significant difference(P>0.05). SE were compared at 7d and 6mo after operation, showed no significant difference(P>0.05)

CONCLUSION: Compared with 120μm group, corneal cap design SMILE operation in 110μm group are more prone to OBL and difficult separation of lens, thus affects UCVA and postoperative recovery rate. There is no significant difference in long-term UCVA.