Application of spherical lens with 0.05 D intervals in optometry for small incision lenticule extraction in myopic eyes

Objective

To investigate the clinical value of spherical lens with 0.05 D intervals in optometry for small incision lenticule extraction (SMILE) in myopic eyes.

Methods

A randomized controlled clinical study was conducted.Sixty patients (120 eyes) with low to moderate myopia and myopic astigmatism who underwent SMILE in the 989th Hospital of the PLA from June 2021 to February 2022 were enrolled.The patients were randomly divided into 0.05 D interval group (optometry with spherical lens at 0.05 D interval) and 0.25 D interval group (optometry with spherical lens at 0.25 D interval), with 30 cases (60 eyes) in each group.There was no significant difference in matched age, sphericity, cylindricity, and best corrected visual acuity (BCVA) (all at P>0.05). The preoperative monocular red-green balance, 1- and 3-month postoperative monocular red-green balance, uncorrected visual acuity and spherical equivalent of both groups were compared.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of the 989th Hospital of the PLA (No.WZLL-2021-034). Written informed consent was obtained from each subject before any medical examination.

Results

The preoperative red-green balance rate in 0.05 D interval group was 95.00%(57/60), which was higher than 35.00%(21/60) in 0.25 D interval group, showing a statistically significant difference (Wald χ²=17.642, P<0.001). The 1- and 3-month postoperative red-green balance rates in 0.05 D interval group were 63.33%(38/60) and 56.67%(34/60), which were higher than 23.33%(14/60) and 21.67%(13/60) in 0.25 D interval group respectively, showing statistically significant differences (Wald χ²=9.137, P=0.003; Wald χ²=7.483, P=0.006). The 1- and 3-month postoperative visual acuity in 0.05 D interval group were -0.1(-0.1, -0.1) and -0.1(-0.1, -0.1), which were higher than 0.0(-0.1, 0.0) and -0.1(-0.1, 0.0) in 0.25 D interval group respectively, showing statistically significant differences (Wald χ²=11.624, P=0.001; Wald χ²=12.841, P<0.001). The 1- and 3-month postoperative spherical equivalent were -0.07(-0.25, 0.13)D and -0.13(-0.25, 0.13)D in 0.05 D interval group, which were higher than -0.13(-0.38, 0.25)D and -0.13(-0.38, 0.25)D in 0.25 D interval group respectively, showing no statistically significant difference between the two groups (Wald χ²=0.029, P=0.866; Wald χ²=0.189, P=0.664).

Conclusions

Compared with spherical lens at 0.25 D interval, 0.05 D interval can improve the accuracy of preoperative and postoperative red-green balance rate and postoperative visual acuity in patients with low to moderate myopia who undergo SMILE.

Optometry; Myopia; Corneal surgery, laser; Duochrome test; Small incision lenticule extraction