Analysis of Corneal Refractive Power Following SMILE Procedure

Objective The main purpose of this study is to investigate the changes of corneal focusing ability after SMILE surgery. We used various measurement methods and collected a lot of information to study this problem. The results of the study aim to provide specific details to help ophthalmologists choose the most suitable intraocular lens for those who have cataract and have undergone vision correction surgery before. Methods From September 2020 to January 2021, we conducted a clinical study on 37 people (70 eyes) who had undergone SMILE surgery in Myopia Laser Treatment Center of our hospital. All participants came back for reexamination within three months after the operation. We made a comprehensive examination before and after the operation, including subjective and objective optometry, IOLMaster biometrics and Pentacam anterior segment imaging. Pentacam equipment generated data of SimK, TNP and TCRP, and equivalent corneal curvature readings (EKR) with diameters of 3 mm, 4 mm and 5 mm, and each measurement was centered on the pupil. The Km value is obtained from the evaluation of IOL Master. We compared and analyzed the refractive changes (△SimK, △TNP, △TCRP, △EKR and △Km) after operation with the refractive changes (△SE) on corneal surface. SPSS 22.0 software is used for statistical processing, including Kolmogorov-Smirnov test to see whether the data is normally distributed, variance analysis, paired t test and Pearson correlation analysis. Results According to SMILE procedure, the measurement results of TCRP4 mm and EKR4.5 mm remained stable, and no obvious changes were found (P > 0.05). There was no obvious relationship between the change of TCRP4 mm (△TCRP4 mm) and the change of spherical lens degree (△SE) (P > 0.05). However, there is a strong correlation between △TCRP4 mm and △SE, and the correlation coefficient is r = 0.989. In addition, the consistency among △TCRP5 mm, △TCRP4 mm and △SE is also very high, and the 95% consistency ranges from − 0.47 to 0.11 D and − 0.32 to 0.50 D respectively. Conclusion Although Pentacam is the most accurate method for measuring TCRP4mm after corneal refractive surgery, it requires further verification and improvement before it can be widely used in combination with the existing intraocular lens calculation formula.