Belaidi A, Pierscionek B K
Department of Biomedical Sciences, University of Ulster, Coleraine, UK.
J Vis. 2007 Aug 3;7(11):1.1-12. doi: 10.1167/7.11.1.
The effects of material properties and equatorial stretching forces on the stress distribution and shape profile of human lenses were investigated to see whether support could be found for either or both current theories of accommodation. Finite element analysis was used to create models using shape parameters and material properties from published data. Models were constructed for two lenses of different ages. Material properties were varied to show differences between models with a single elastic modulus and those with different moduli for the cortex and the nucleus. Two levels of stretching forces were applied at the equator. Comparisons between experimental and model profiles were made, and stress distribution patterns were constructed. In all models, stretching produces a flattening in the peripheral curvature of the lens. In the younger lens, model and experimental results show that central curvature at some points is steeper for stretched than for unstretched profiles. In the older lens, gradients are flatter at all central points for stretched model and experimental profiles compared to the unstretched profile. In all models, there is a region of higher stress distribution within the lens that corresponds with the position of an inflection point that appears on the anterior surface and, in the older lens, also on the posterior surface. The results show that equatorial stretching forces can produce shape changes in support of both current theories of accommodation depending on the lens age, shape, and applied force.
研究了材料特性和赤道拉伸力对人晶状体应力分布和形状轮廓的影响，以确定是否能为当前的一种或两种调节理论找到支持。使用有限元分析，根据已发表数据中的形状参数和材料特性创建模型。针对两个不同年龄的晶状体构建模型。改变材料特性以显示具有单一弹性模量的模型与皮质和核具有不同模量的模型之间的差异。在赤道处施加两级拉伸力。对实验轮廓和模型轮廓进行比较，并构建应力分布模式。在所有模型中，拉伸都会使晶状体周边曲率变平。在较年轻的晶状体中，模型和实验结果表明，在某些点处，拉伸后的中央曲率比未拉伸轮廓更陡。在较老的晶状体中，与未拉伸轮廓相比，拉伸后的模型和实验轮廓在所有中心点处的梯度更平缓。在所有模型中，晶状体内部存在一个应力分布较高的区域，该区域与出现在前表面且在较老晶状体中也出现在后表面的拐点位置相对应。结果表明，赤道拉伸力可根据晶状体年龄、形状和施加的力产生形状变化，以支持当前的两种调节理论。
