A Nomogram to Improve Predictability of Small-Incision Lenticule Extraction Surgery

BACKGROUND: This study aimed to determine and validate that use of a nomogram could enhance the predictability of small-incision lenticule extraction (SMILE) surgery. MATERIAL/METHODS: 195 eyes from 98 patients were enrolled in group 1, and 46 eyes from 26 patients in group 2. Uncorrected and corrected distance visual acuity (UDVA and CDVA), manifest refraction spherical equivalent (SE) preoperatively and 1 day, 1 week, 1 month, and 3 months postoperatively were measured. A nomogram based on the error in SE correction was generated by using multifactor regression method in group 1. After applying this nomogram to redesign the refraction target, the predictability, safety, and efficacy of the SMILE procedure were determined. RESULTS: A linear regression formula (SE error=0.259+0.113×SE(preoperative)) was derived as a nomogram to adjust the SE target. In group 2, the predictability of error was 86.21% within 0.50 D and 97.83% within 1.00 D, compared with 70.25% and 95.90%, respectively, in group 1. The use of the nomogram significantly reduced the variance in postoperative SE. The efficacy and safety of SMILE did not differ significantly in the 2 groups 3 months postoperatively. CONCLUSIONS: The nomogram can optimize the target refractive prediction of the SMILE procedure without compromising safety and efficiency.