膨胀法加压兔角膜前表面与后表面所测生物力学性能的比较

摘要

目的 研究比较膨胀法加压角膜前、后表面所测角膜生物力学性能的差异.方法 实验研究.8只日本大耳白兔纳入本研究.实验开始前测量角膜的厚度、直径和眼内压.每只白兔被随机选取一只眼膨胀法加压角膜的前表面(前表面加压眼组,n=8),另一只眼加压角膜的后表而(后表面加压眼组,n=8),加压范围为1.1～44.0 mmHg,记录角膜顶点前突位移值,然后采用板壳理论公式获得角膜的应力-应变关系、正切弹性模量和滞后量.两眼角膜厚度、直径、眼压、正切弹性模量和滞后量的比较均采用配对t检验进行分析.结果 两眼之间角膜平均厚度、直径、眼压差异无统计学意义(厚度:t=-0.073,P＞0.05；直径:t=0.260,P＞0.05;眼压:t=- 1.033,P＞0.05).后表面加压眼组测得的角膜正切弹性模量值大于前表面加压眼组,且差异有统计学意义(t=6.664、6.681、6.931,P＜0.01)；前表面加压眼组的角膜滞后量明显大于后表面加压眼组,分别为2.50×104 MPa和1.94×10-4 MPa,差异有统计学意义(t=-2.891;P＜0.05).结论 加压角膜后表面所测得的角膜硬度明显大于加压前表面.角膜作为非线性黏弹性组织,不仅在冠状面上表现出区域硬度的非对称性,而且在矢状面上也表现出硬度的非对称性.本实验研究结果对今后眼内压的校正具有一定参考价值.%Objective To investigate and compare the corneal biomechanical properties obtained by inflating the corneal anterior surface and posterior surface.Methods In this experimental study.Eight Japanese white rabbits were included.One eye was randomly selected from each rabbit and was subjected to anterior pressure in an inflation test rig (anterior surface pressuring eyes group,n=8),and the contralateral eye was subjected to posterior pressure (posterior surface pressuring eyes group,n=8).The pressure range was 1.1-44.0 mmHg.Corneal apical displacement was recorded,then the shell theory was used to deduce the stress-strain relationship,tangent elastic modulus and hysteresis.Corneal thickness,diameter and intraocular pressure (IOP) were measured before the inflation test.A paired t test was used to analyze and compare corneal thickness,diameter,IOP,tangent elastic modulus and hysteresis values.Results Differences in the average corneal thickness,diameter and IOP were not statistically significant between the two groups (thickness:t=-0.073,P＞0.05;diameter:t=0.260,P＞0.05; IOP:t=-1.033,P＞0.05).Corneas tested under posterior pressure displayed significantly higher stiffness than those inflated by anterior pressure (t=6.664,6.681,6.931,P＜0.01).The hysteresis values of the anterior surface pressuring eyes group were significantly greater than those of the posterior surface pressuring eyes,the values were 2.50×10-4 MPa and 1.94×10-4 MPa,respectively.The difference was statistically significant (t=-2.891,P＜0.05).Conclusion Corneal specimens inflated posteriorly were significantly stiffer than those inflated anteriorly.As a nonlinear viscoelastic tissue,the cornea not only presented region-associated stiff asymmetry in the coronal plane,but also presented stiff asymmetry in the sagittal plane.The experimental results could have an reference value in correcting IOP readings in the future.