Department of Structures for Engineering and Architecture, University of Naples "Federico II", Via Toledo 402, 80134, Naples, Italy.
Civil and Environmental Engineering Department, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
Biomech Model Mechanobiol. 2024 Jun;23(3):709-720. doi: 10.1007/s10237-023-01801-7. Epub 2023 Dec 21.
We present a patient-specific finite element model of the human cornea that accounts for the presence of the epithelium. The thin anterior layer that protects the cornea from the external actions has a scant relevance from the mechanical point of view, and it has been neglected in most numerical models of the cornea, which assign to the entire cornea the mechanical properties of the stroma. Yet, modern corneal topographers capture the geometry of the epithelium, which can be naturally included into a patient-specific solid model of the cornea, treated as a multi-layer solid. For numerical applications, the presence of a thin layer on the anterior cornea requires a finer discretization and the definition of two constitutive models (including the corresponding properties) for stroma and epithelium. In this study, we want to assess the relevance of the inclusion of the epithelium in the model of the cornea, by analyzing the effects in terms of uncertainties of the mechanical properties, stress distribution across the thickness, and numerical discretization. We conclude that if the epithelium is modeled as stroma, the material properties should be reduced by 10%. While this choice represents a sufficiently good approximation for the simulation of in vivo mechanical tests, it might result into an under-estimation of the postoperative stress in the simulation of refractive surgery.
我们提出了一种考虑到上皮组织存在的人眼角膜的特定于个体的有限元模型。作为角膜的最外层，其具有抵御外部作用的功能，从力学角度来看，它的作用微乎其微，而且在大多数角膜的数值模型中都被忽略了，这些模型将整个角膜的力学特性都赋予了基质。然而，现代角膜地形仪可以捕捉到上皮组织的几何形状，它可以自然地纳入眼角膜的特定于个体的固体模型中，作为一个多层固体进行处理。对于数值应用来说，角膜前表面的薄层需要更精细的离散化，并且需要为基质和上皮组织定义两个本构模型（包括相应的特性）。在这项研究中，我们希望通过分析力学性能不确定性、厚度方向的应力分布和数值离散化等方面的影响，来评估纳入上皮组织对角膜模型的重要性。我们得出的结论是，如果将上皮组织建模为基质，那么材料性能应该降低 10%。虽然这种选择对于模拟体内力学测试来说是一个足够好的近似值，但在模拟屈光手术时，可能会低估术后的应力。
