LASIK术后角膜变形和应力的有限元分析

Finite Element Analysis of Corneal Deformation and Stress after LASIK

目的:研究准分子激光原位角膜磨镶术(LASIK)后角膜的变形及内力变化,探究矫正屈光度、术前角膜厚度对术后角膜生物力学的影响。方法:采用Gasser-Holzapfel-Ogden超弹性本构关系描述角膜材料的力学行为,建立术前和术后人眼角膜生物力学的有限元模型,计算LASIK术前、术后角膜后表面中央点的位移差,分析不同矫正屈光度和术前角膜厚度对术后角膜变形和Mises应力的影响。结果:LASIK手术前后角膜后表面中央点位移差随矫正屈光度的变化呈非线性递增。在矫正屈光度较低时,LASIK术前角膜厚度对手术前后角膜后表面中央点位移差影响较弱,在矫正屈光度较高时影响比较明显。结论:矫正高度数屈光度情况下角膜厚度对术后角膜生物力学稳定性影响较大,LASIK由于角膜瓣的存在容易引起术后角膜应力增加。

Objective:We performed finite element analysis of corneal deformation and stress after laser in situ keratomileusis(LASIK)to study the influence of corrective diopter and preoperative corneal thickness on postoperative corneal biomechanical characteristics.Methods:The mechanical behavior of human corneal material was described through Gasser-Holzapfel-Ogden hyperelastic constitutive modeling.The preoperative and postoperative finite element models of corneal biomechanics were established,and the displacement differences of corneal posterior surface center after LASIK were calculated.The effects of different corrective diopters and preoperative corneal thicknesses on postoperative corneal deformation and Mises stress were analyzed.Results:The displacement difference of the corneal posterior surface center before and after LASIK surgery nonlinearly increased with the corrective diopter.The effect of preoperative corneal thickness on the displacement difference of the corneal posterior surface center was weaker for lower corrective diopters and stronger for higher ones.Conclusions:For higher diopters,corneal thickness had significant effect on postoperative corneal biomechanical stability.Due to the existence of the corneal flap,LASIK surgery is likely to cause increments of postoperative corneal stress.