Biomechanical Comparison of PRK, LASIK, and KLEx Using Personalized Finite Element Simulations

Purpose: To investigate the biomechanical effects of photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and keratorefractive lenticule extraction (KLEx) on postoperative corneal biomechanics and visual outcomes using patient-specific finite element simulations. Methods: A cohort of 30 patients (24 ± 4 years) undergoing PRK, LASIK, or KLEx was modeled using finite element simulations. Patient-specific preoperative topographies informed the creation of surgical models with ablation and lenticule profiles tailored to the correction needs of each patient based on the same theoretical ablation profile across the three refractive procedures. The parameters of the mechanical model were calibrated using experimental data from human corneal tissue. Results: Simulations showed a consistent undercorrection of the refractive targets for all procedures, which increased with higher spherical corrections. PRK showed the lowest undercorrection, followed by LASIK and KLEx. Procedure-specific correction factors were calculated to compensate for the biomechanical response and achieve the correction required for the patient: the spherical component should be multiplied by 1.40 for PRK, 1.57 for LASIK, and 1.71 for KLEx. Stress analysis revealed that PRK maintained a uniform anterior stress distribution (28% increase from preoperatively), whereas LASIK (53% increase from preoperatively) and KLEx (44% increase from preoperatively) concentrated stress in the posterior stroma. Conclusions: Although the same volume of tissue was removed in all procedures, corneal biomechanics influence refractive surgery outcomes, with PRK offering advantages in terms of reduced undercorrection and more favorable stress distribution. PRK's conservative approach offers a greater biomechanical safety margin, making it the recommended option for suspiciously weak corneas.