Differences in the Corneal Biomechanical Responses to LASIK and KLEx Based on Parametric Numerical Simulation.

Purpose: To use parametric numerical simulation to characterize and compare the differences in corneal biomechanical responses to laser in situ keratomileusis (LASIK) and keratorefractive lenticule extraction (KLEx) under various surgical settings.

Methods: The Finite Element Model was used in a parametric study to evaluate corneal biomechanical responses to LASIK and KLEx, considering variations in preoperative corneal thickness, corneal flap/cap thickness and diameter, refractive correction, and optical zone diameter. Surgery-induced stress, displacement, and interface contact pressure were compared between LASIK and KLEx using the Wilcoxon signed-rank test. Spearman correlation analysis explored the correlation of the biomechanical response differences between surgeries with various parameters.

Results: LASIK induced more stress reductions and displacements than KLEx in corneal flap/cap (P < .001). Both surgeries introduced a centralizing redistribution of stress and displacement in the stroma (ie, stress increased with outward stromal displacement at the center), and stress decreased with inward displacement in the periphery. Stromal stress and displacement were higher after LASIK than after KLEx (P < .001). Corneas after KLEx exhibited higher contact pressure than those after LASIK (P < .001). With the significant increase in preoperative corneal thickness, refractive correction, optical zone diameter, and decreased flap/cap thickness, the biomechanical differences between surgeries were notably reduced, with most Spearman correlation coefficients (|r|) being greater than 0.3 (eg, stress and displacement differences at the stromal center reduced by 36.69% and 82.17% from refractive correction of -1.00 to -9.00 diopters).

Conclusions: Finite element simulations indicate that KLEx may provide improved corneal stability compared to LASIK under comparable surgical conditions. However, this biomechanical advantage is not absolute and depends on multiple factors, including refractive correction magnitude, central corneal thickness, and flap or cap thickness. These findings suggest that as refractive correction increases, cap or flap thickness decreases, or central corneal thickness increases, the biomechanical differences between KLEx and LASIK diminish. In certain cases, KLEx may exhibit biomechanical risks comparable to LASIK. These results highlight the need for a personalized approach in refractive surgery planning, considering both biomechanical and surgical complexity factors.