Purpose To determine the effect of lowering laser energy on clinical outcomes in small-incision lenticule extraction (SMILE). Design Prospective randomized clinical trial. Methods A total of 151 patients (151 eyes) with moderate myopia scheduled for SMILE were included: 58 eyes received SMILE with low energy (100, 105, and 110 nJ; L-SMILE group) and 93 with conventional energy (115–150 nJ; C-SMILE group). Patients received complete ophthalmic examinations preoperatively and over 3 months postoperatively. Results Uncorrected distance visual acuity (logMAR UDVA) 1 day and 1 week postoperatively was significantly better in L-SMILE than in C-SMILE (P <.001 and P =.005, respectively). There was no significant difference between the groups at 1 and 3 months. L-SMILE induced significantly fewer corneal aberrations compared with C-SMILE at 1 week and 1 month postoperatively (both P <.01), but there were no significant differences at 3 months. Though there was no difference in logMAR UDVA over the postoperative period between the 100, 105, and 110 nJ subgroups, there was a significant difference in logMAR UDVA on postoperative day 1 between L-SMILE and each subgroup in which an energy level of 115 nJ or higher was used. Furthermore, logMAR UDVA on postoperative day 1 showed a significant correlation with laser energy (r = 0.451, P <.001) and multiple linear regression analysis revealed that energy level was the only independent factor associated with logMAR UDVA on postoperative day 1 (P <.001). Conclusions SMILE using femtosecond energy of less than 115 nJ facilitates better visual acuity with less induction of corneal aberrations in the early postoperative period.
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