Long-term changes in corneal densitometry and associated factors following small incision lenticule extraction for moderate and high myopia.

Purpose: To investigate long-term trends in corneal densitometry and associated influencing factors following small incision lenticule extraction (SMILE).

Methods: A comparative study was performed among 72 eyes of 38 patients undergoing SMILE. Eyes were divided into moderate myopia [mean spherical equivalent (SE),-4.22 ± 0.68D] and high myopia (mean SE,-7.63 ± 1.09 D) groups. Visual acuity, manifest refraction, corneal topography and corneal densitometry (CD) were evaluated preoperatively and 3 years postoperatively.

Results: The efficacy indices at last postoperative follow-up (42.47 ± 0.51 months) were 0.92 ± 0.21 and 0.97 ± 0.22, the safety indices were 1.12 ± 0.17 and 1.14 ± 0.21 for high and moderate myopia, respectively (all > 0.05). CD values in the 0-6 mm zone of the posterior corneal layer was statistically significantly lower than the preoperative values in both groups. Postoperative CD values (0-2 mm zone) in the posterior layer of the high myopia group were statistically significantly lower than in the moderate myopia group ( = 0.025); CD values (2-6 mm zone) in the anterior layer were higher in the high myopia group ( = 0.026). Correlation analyses showed that CD values in the 0-2 mm middle layer were negatively correlated with lenticule thickness in high myopia ( = -0.411, = 0.016); there was a negative correlation between the CD values (0-6 mm) and corneal oblique trefoil in this group ( < 0.05).

Conclusion: Corneal transparency in the 0-6 mm zone of the posterior cornea increased following SMILE in moderate and high myopia. Long-term CD values in high myopia may be correlated with oblique trefoil and lenticule thickness.