Elsheikh Ahmed, Ross Stuart, Alhasso Daad, Rama Paolo
Division of Civil Engineering, University of Dundee, Dundee, United Kingdom.
Curr Eye Res. 2009 Jan;34(1):26-35. doi: 10.1080/02713680802535263.
The study aimed to improve the accuracy of corneal numerical simulation by adopting a better representation of the corneal layered structure. The study considered both the shear and tensile behavior of the interface surfaces between stromal lamellae, and assessed the effect of modeling the cornea's three main layers-the epithelium, stroma, and endothelium with their respective material properties.
Twelve human donor corneas were tested to determine the behavior of the stroma under surface shear. Numerical models were then built to consider the stromal inter-lamellar adhesion, which included the shear behavior determined experimentally and the tensile behavior available in the literature. They also adopted the distinctive material properties of the epithelium, stroma, and endothelium. The numerical models simulated corneal behavior under intraocular pressure elevation, concentric anterior pressure, and the conditions under tonometry with the Goldmann applanation tonometer.
The stress-strain shear behavior of stromal tissue followed an exponential pattern, with an initial low stiffness increasing gradually under higher stresses. This behavior was adopted in the numerical simulation to set the level of adhesion between stromal layers. Considering that the stromal inter-lamellar adhesion and the distinctive material properties of corneal layers had a significant effect in simulating the response to concentrated anterior pressures, which cause bending of corneal tissue, this was almost unnecessary when predicting the effect of intraocular pressure, which put the cornea under membrane tension.
The corneal layered structure affects the results of numerical simulations especially in problems where the cornea is subjected to bending effects.
本研究旨在通过更好地呈现角膜分层结构来提高角膜数值模拟的准确性。该研究考虑了基质薄片之间界面的剪切和拉伸行为，并评估了对角膜三个主要层——上皮层、基质层和内皮层及其各自材料特性进行建模的效果。
对12个人类供体角膜进行测试，以确定基质在表面剪切作用下的行为。然后建立数值模型来考虑基质层间粘附，其中包括通过实验确定的剪切行为和文献中可得的拉伸行为。他们还采用了上皮层、基质层和内皮层独特的材料特性。数值模型模拟了眼压升高、同心前压力以及使用戈德曼压平眼压计进行眼压测量时的角膜行为。
基质组织的应力 - 应变剪切行为呈指数模式，在较低应力下初始刚度较低，在较高应力下逐渐增加。这种行为被用于数值模拟中以设定基质层之间的粘附水平。考虑到基质层间粘附和角膜各层独特的材料特性在模拟对导致角膜组织弯曲的集中前压力的响应时有显著影响，而在预测使角膜处于膜张力下的眼压影响时这几乎是不必要的。
角膜分层结构会影响数值模拟结果，特别是在角膜受到弯曲效应的问题中。
