Abstract
Purpose :
To compare the changes of biomechanical properties, endothelial cell density (ECD), higher-order aberrations, and posterior corneal elevation (PCE) of Femtosecond Small Incision Lenticule Extraction (SMILE) at depths of 100 um, 120um, 140um and 160um
Methods :
This retrospective, comparative case series was designed to assess outcomes following SMILE procedures performed at a large surgical center by cornea specialists between May 1, 2020 and September 30, 2021. Four cap depth settings were compared: 100 um, 120um, 140um and 160um. Preoperative corneal biomechanical properties, posterior corneal elevation (PCE), total high-order aberrations (THOA), and endothelial cell density (ECD) by Scheimpflug Tomography (Pentacam AXL) , Dynamic Scheimpflug analyzer (Corvis ST) and specular microscopy (Konan SP 9000-LC) respectively, were measured preoperatively and on days 1, 7, 30 and 90 postoperative.
PCE changes by Pentacam were calculated at the corneal apex. Three parameters including deformation amplitude (DA), first applanation time (A1T), and second applanation time (A2T) were chosen for analysis, and then the ECD was automatically calculated by the computer software.
Results :
A total of 140 patients (280 eyes) met the inclusion criteria: 70 eyes in 100nm cap depth SMILE group, 700 eyes in 120nm cap depth SMILE group, 70 eyes in 140nm cap depth SMILE group and 700 eyes in 160nm cap depth SMILE group.
Neither deformation amplitude (DA) nor the first applanation time (A1T) were significantly different between the groups. The second applanation time (A2T) was similar between the groups on days 1, 7, 30 with the exception of 90 days after surgery (22.52±0.18 ms in the 160-cap group versus 22.02 ±0.23 ms in the 140-cap group versus 21.84 ±0.24 ms in the 120-cap group versus 21.34 ±0.34 ms in the 100-cap group, p = 0.004). DA curve depth(µm) was steeper in the 100um depth cap, and the curve will be reduced as the SMILE has a deeper cap. AT2 will be significantly shorter in the 100um depth cap SMILE than in the 160um depth cap. No statistically significant differences were found between the different depth groups regarding THOA, ECD, CV and HEX.
Conclusions :
A deeper cap while performing SMILE (140-160um) has less biomechanical effect in the cornea than SMILE with a cap created at 100-120 um.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.