AIM: To explore the effect of different energy parameters of femtosecond laser small incision lenticule extraction(SMILE)on stage Ⅰ opaque bubble layer(OBL)and visual quality.

METHODS: A retrospective analysis of the clinical data of 216 patients(432 eyes)who came to our hospital for SMILE surgery from July 2018 to December 2019. According to whether stage Ⅰ OBL occurred, they were divided into OBL group(42 eyes)and non-OBL group(390 eyes). The age, visual acuity parameters, corneal parameters, microlens parameters and energy parameters were compared between the two groups, and multivariate regression analysis was used to analyze the relationship between the difference in energy settings and the OBL of stage Ⅰ. The uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA), and modulation transfer function cut-off spatial frequency(MTF_cut-off), Strehl Ratio(SR)and Objective Scattering Index(OSI)with energy parameters of 130, 135, 140, 145, and 150 nJ before and 1mo after surgery were compared. The correlation between energy parameters and stage Ⅰ OBL, UCVA, BCVA, MTF_cut-off, SR, OSI were analyzed.

RESULTS: Multivariate regression analysis showed that the energy setting with a difference of 5nJ did not show an association with stage Ⅰ OBL. In the different energy parameter groups, LogMAR UCVA, MTF_cut-off, and OSI at 1mo after surgery were improved compared with preoperatively(P<0.05), and the difference between the groups were statistically significant(F=75.712, 15.304, 26.293, all P<0.05). SMILE intraoperative energy parameters were negatively correlated with UCVA(r=-0.272), MTF_cut-off(r=-0.132), and OSI(r=-0.151)1mo after surgery(P<0.05).

CONCLUSION: When using a 4.5μm dot pitch, in the usual energy range, the lower the energy, the better the postoperative visual quality, but it does not significantly affect the incidence of stage Ⅰ OBL during SMILE surgery.