Mathematical models of laser correction of myopia by LASIK, SMILE and PRK methods

The stress-strain state of the human eye, which cornea in its apexis is weakened after myopia surgical correction, is studied. The elastic system “cornea-sclera” is presented as two joint transversely isotropic spherical segments with tapered thickness, different radii of curvature and biomechanical properties. Cornea is modeled as multilayer shell. The simulated eye shell is loaded with internal pressure. Mathematical models of three different laser vision correction surgeries: small incision lenticule extraction (SMILE), laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK), are developed in the engineering simulation software ANSYS Inc. The diameter and thickness of the lenticular in SMILE, the diameter of the ablation zone and the maximum thickness (depth) of the corneal ablation in LASIK and PRK define optical surgery areas and are considered as comparable parameters. Finite element simulation shows that after LASIK vision correction the apex of the cornea has a greater displacement and the stress increase greater in the stroma than after SMILE and PRK.