Schumacher Justin, Lopez Raymundo Rodriguez, Larin Kirill, Manns Fabrice, Scarcelli Giuliano
Fischell Department of Bioengineering, University of Maryland, College Park, United States of America.
Department of Biomedical Engineering, University of Houston, Houston, TX, United States of America.
JPhys Photonics. 2024 Jul 1;6(3):035021. doi: 10.1088/2515-7647/ad3e55. Epub 2024 Jul 2.
Lens biomechanical properties are critical for our eyes to accommodate. While it is well understood that lens mechanical properties change with age, different experimental techniques have been used over the years, with varying results on how the lens modulus changes. In this study, we developed a spatial-varying elasticity model to characterize the overall elastic modulus of the lens and establish its effect on accommodation. First, to validate the model, ex vivo porcine lenses underwent compression testing using biopsy punches of different diameters to change the percentage of nucleus within samples. Importantly, we found that, indeed, changing nucleus/cortex spatial ratio produces dramatic (∼7-fold) increase in overall sample modulus. Comparing the model with human lens spatial ratios, we demonstrate how changing spatial mechanics are more influential than peak modulus changes on overall elastic modulus. Next, in vivo clinical measurements of the spatial-varying lens modulus were used to generate a simplified mechanical-optical model of accommodation. We defined an ellipsoid lens with patient-derived modulus and geometry measurements, and a statics simulation and ray tracing analysis were performed through the deformed and undeformed lens. The resulting accommodation estimates agree with general accommodation expectations.
晶状体的生物力学特性对于我们眼睛的调节功能至关重要。虽然人们很清楚晶状体的机械性能会随着年龄的增长而变化，但多年来使用了不同的实验技术，关于晶状体模量如何变化的结果也各不相同。在本研究中，我们开发了一种空间变化弹性模型，以表征晶状体的整体弹性模量，并确定其对调节功能的影响。首先，为了验证该模型，对离体猪晶状体进行了压缩测试，使用不同直径的活检穿刺器来改变样本中的核的百分比。重要的是，我们发现，实际上，改变核/皮质的空间比例会使整个样本模量显著增加（约7倍）。将该模型与人类晶状体的空间比例进行比较，我们证明了空间力学的变化比峰值模量的变化对整体弹性模量的影响更大。接下来，利用晶状体模量空间变化的体内临床测量结果，生成了一个简化的调节机械光学模型。我们定义了一个具有患者来源的模量和几何测量值的椭球形晶状体，并通过变形和未变形的晶状体进行了静态模拟和光线追踪分析。由此得出的调节估计结果与一般的调节预期相符。
