Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China.
School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China.
Biomed Eng Online. 2019 Apr 4;18(1):42. doi: 10.1186/s12938-019-0662-1.
Corneal biomechanical properties are important for the diagnosis of corneal diseases, individualized design and prognosis of corneal surgery. Clinical available devices such as Ocular Response Analyzer (ORA) and Corneal Visualization Scheimpflug Technology (Corvis ST) can provide corneal biomechanics related parameters, while corneal elastic modulus cannot be extracted directly from them at present. The aim of this study is to suggest a method to determine corneal elastic modulus based on the results of Corvis ST test according to Reissner's theory on the relation between stress and small displacement in shallow spherical shell.
Five rabbits (10 eyes) and 10 healthy humans (20 eyes) were measured with Corvis ST to obtain the normal range of corneal elastic modulus. Results showed Corneal elastic modulus of rabbit was 0.16 MPa to 0.35 MPa, human corneal elastic modulus was 0.16-0.30 MPa. Rabbit corneas were also measured at different intraocular pressures (IOP), and results showed corneal elastic modulus, first applanation time (A1T) and stiffness parameter (SP-A1) were positively correlated with IOP. Deformation amplitude (DA), the second applanations time (A2T), and peak distance (PD) were negatively correlated with IOP. Finite element method was used to simulate the Corvis measurements according to the calculated elastic modulus and the simulated corneal apical displacements were agreement with experimental results in general.
The method to determine corneal elastic modulus based on Corvis test according to the relationship between force and displacements of shallow spherical shell is convenient and effective.
角膜生物力学特性对于角膜疾病的诊断、角膜手术的个体化设计和预后具有重要意义。临床可用的设备，如眼反应分析仪（ORA）和角膜可视化Scheimpflug 技术（Corvis ST），可以提供与角膜生物力学相关的参数，但目前无法直接从这些设备中提取角膜弹性模量。本研究旨在根据 Reissner 关于浅球壳中应力与小位移关系的理论，提出一种基于 Corvis ST 测试结果确定角膜弹性模量的方法。
对 5 只兔子（10 只眼）和 10 名健康人（20 只眼）进行 Corvis ST 测量，得出了角膜弹性模量的正常范围。结果表明，兔角膜弹性模量为 0.16-0.35 MPa，人角膜弹性模量为 0.16-0.30 MPa。还对不同眼内压（IOP）下的兔角膜进行了测量，结果表明角膜弹性模量、第一次压平时间（A1T）和刚性参数（SP-A1）与 IOP 呈正相关，变形幅度（DA）、第二次压平时间（A2T）和峰距（PD）与 IOP 呈负相关。根据计算出的弹性模量，使用有限元法模拟 Corvis 测量，模拟角膜顶点位移与实验结果总体上一致。
根据浅球壳中力与位移的关系，通过 Corvis 测试确定角膜弹性模量的方法方便有效。
