Changes Of Corneal Densitometry After SMILE And FS-LASIK Surgery In Patients With High Myopia

Objective To observe the changes of corneal densitometry(CD)after small incision lenticule extraction(SMILE)and femtosecond laser-assisted laser in situkeratomileusis(FS-LASIK)in patients with high myopia and its relevant factors.Methods Retrospective study.High-myopia patients who received SMILE and FS-LASIK surgery in the Optometry Center of Ningxia Eye Hospital from 2018-11 to2020-11 were selected,including 40 patients(40 eyes)in SMILE group and 41 patients(41eyes)in FS-LASIK group.The CD was measured with the Pentacam system analysis before surgery and postoperatively at 1、3 and 6 months.The diameter ranges of 0～2 mm、2～6 mm、6～10 mm as well as the anterior、middle、posterior and full-thickness CD with the apex of the cornea were recorded.The differences of two groups in various corneal layers and concentric radial zones were compared using Two-way Repeated measures Anova.Mann-whitney U test was performed for comparison between the two groups at the same time point.Spearman test was used to analyze the correlation between SE,ablation depth,rest thickness and CD.Results At 6 months,both of SMILE and FS-LASIK group,there were significant differences between the preoperative and postoperative CD values in different diameter ranges and corneal layers(all p<0.05),and the values were lower than preoperative.At 1months,there were statistical significance of CD in 6～10mm anterior layer and total layer between the two groups(Z=-2.570、-2.259;P=0.010、0.024,respectively),however,the differences were disappeared at 3 months.The anterior layers of CD at 1 month was found positively correlated with ablation depth for the FS-LASIK group(Z=0.451、0.506、0.411;p=0.004、0.001、0.009).Conclusion In the early stage,the anterior layers of CD increased temporarily after SMILE and FS-LASIK surgery for patients with high myopia,thereinto FS-LASIK group was higher than SMILE group at 6～10 mm diameter range.However,the CD decreased over time until slightly lower than preoperative level.There was a weak positive correlation between anterior layers of the CD and ablation depth after FS-LASIK.