Comparison Of Corneal Biomechanics After FS-LASIK And SBK For Low To Moderate Myopia And Analysis Of Associated Factors

Purpose:The purpose of this study was to compare the changes in corneal thickness and related corneal biomechanical parameters in low to moderate myopic patients with the same programmed optical zone(POZ)and similar refractive status after excimer laser in situ keratomileusis(FS-LASIK)with femtosecond laser flap making and sublaminar laser keratomileusis(SBK)with anterior elastography,and to analyze the related influencing factors.Method:1.This is a prospective study of 53 patients(91 eyes)with low to moderate myopia in one or both eyes who presented at the Affiliated Hospital of Inner Mongolia Medical University from November 2021 to July 2022 and voluntarily underwent refractive surgery treatment.All eyes included in the study had a preoperative equivalent spherical lens ≤-6.00 D.Based on patient preference and physician recommendation,36(64 eyes)underwent FS-LASIK and 17(27 eyes)underwent SBK surgery.2.All patients included in the study completed routine preoperative examinations,including refraction,intraocular pressure,naked eye visual acuity,best corrected visual acuity,Corneal Visualization Scheimpflug Technology(Corvis ST),and a three-dimensional preoptic nodal measurement assessment system(Pentacam HR)examination,etc.Corneal topography was performed in all patients at 1 day,1 month,3 months,and 6 months postoperatively using the Pentacam HR to obtain corneal biomechanical parameters,including the thinnest corneal thickness(TCT),corneal volume(CV),deviation of the mean velocimetric progression(deviation of the averaged pachymetric progression(Dp),deviation of the cornal thickness at the thinnest point(Dt),and deviation of the parameter Ambrosio relative thickness(Dt).deviation of the parameter Ambrosio Relational Thickness,Da)and the total "D" value(a sixth term is the final overall map reading taking each of the parameters into account,D each of the parameters into account,D),etc.3.In this study,we compared the differences in naked eye visual acuity,spherical lens,columnar lens,and equivalent spherical lens after FS-LASIK and SBK surgery.Also,we compare whether there is a significant difference in TCT and CV after the two procedures and explore whether there is a significant difference in corneal biomechanical parameters at different time points after FS-LASIK and SBK procedures.Finally,we will analyze in depth the correlation between the parameters with differences and TCT and CV to clarify the factors influencing the differences in corneal biomechanics.4.SPSS software(version 22.0)was used for statistical analysis.Data conforming to a normal distribution were expressed using the mean ± standard deviation(means ± SD),and data with a skewed distribution were expressed using the median and interquartile spacing.For data conforming to a normal distribution,the independent samples t-test was used for comparison,while for data with a skewed distribution,we used the Mann-Whitney U test for comparison.ANOVA was used to examine the differences between corneal thickness progression parameters at different time points,and Spearman or Pearson correlation analysis was used to explore the relationship between postoperative corneal thickness and corneal volume and corneal thickness progression parameters.P < 0.05 was considered a statistically significant difference.Result:1.No statistically significant differences were shown in naked visual acuity,spherical lens,columnar lens,and equivalent spherical lens at 1 month,3 months,and6 months after FS-LASIK and SBK(P > 0.05).This suggests that there were no significant differences between the two surgical approaches in terms of postoperative stability,safety,and efficacy.2.The SBK group was smaller than the FS-LASIK group in terms of postoperative TCT and CV and showed a significant difference(P < 0.05).However,there was no significant difference in TCT and CV between the two groups in terms of time.3.In addition,PPIA,Dp,Da and Dt showed decreasing trends at all time points,and TCT and CV showed increasing trends in both groups postoperatively.However,there was no statistical difference in the SBK group for each parameter at time(P >0.05).only PPIA and Da were different in the FS-LASIK group at each time point(P= 0.002;P = 0.007),and there was no statistical difference in the other parameters.4.PPIA,Dp,Dt,Da,and D after both procedures showed a significant negative correlation with postoperative TCT.PPIA,Dp,Dt and Da after FS-LASIK showed a negative correlation with postoperative CV(PPIA: R2 = 0.136,P = 0.003;Dp: 0.149,P = 0.002;Dt: R2 = 0.627,P < 0.001;Da: R2 = 0.254,P < 0.001;D: R2 = 0.184,P <0.001).In contrast,only Dt showed a negative correlation with postoperative CV after SBK(r =-0.702,P < 0.001),while the other parameters showed no correlation.Conclusion:1.Studies have shown that both FS-LASIK and SBK procedures exhibit high safety and stability and are effective in correcting low to moderate myopia.2.FS-LASIK is superior to SBK in terms of postoperative corneal thickness and its associated biomechanical stability.FS-LASIK is superior in the correction of low to moderate myopia and offers a more stable and safe treatment option for patients with low to moderate myopia.3.The changes in corneal biomechanical parameters were correlated with the surgical approach and time,and the changes in PPIA,Dp,Dt,and Da showed a significant negative correlation with corneal thickness.These findings suggest the need to consider the impact of corneal biomechanical properties on postoperative outcomes in surgical selection and postoperative management.