Grytz Rafael, Siegwart John T
Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States.
Invest Ophthalmol Vis Sci. 2015 Mar 3;56(3):2065-78. doi: 10.1167/iovs.14-15352.
To estimate two collagen-specific material properties (crimp angle and elastic modulus of collagen fibrils) of the remodeling tree shrew sclera during monocular -5 diopter (D) lens wear and recovery.
Tensile tests were performed on scleral strips obtained from juvenile tree shrews exposed to three different visual conditions: normal, monocular -5 D lens wear to induce myopia, and recovery. Collagen fibrils are crimped in the unloaded sclera and uncrimp as the tissue stiffens under load. Inverse numerical analyses were performed to estimate the (unloaded) crimp angle and elastic modulus of collagen fibrils using a microstructure-based constitutive model.
Compared with the control eye, the crimp angle was significantly higher in the treated eye after 2 days and remained significantly higher until 21 days of lens wear (P < 0.05). The difference between the crimp angle of the treated and control eye rapidly vanished during recovery in concert with the changes in axial elongation rate. A rapid and extensive increase in the elastic modulus was seen in both eyes after starting and stopping the lens wear.
The estimated change in the crimp of scleral collagen fibrils is temporally associated with the change in axial elongation rate during myopia development and recovery. This finding suggests that axial elongation may be controlled by a remodeling mechanism that modulates the collagen fibril crimp. The observed binocular changes in scleral stiffness are not temporally associated with the axial elongation rate, indicating that scleral stiffening may not be causally related to myopia.
评估在单眼佩戴-5屈光度（D）镜片及恢复过程中，树鼩巩膜重塑时两种胶原蛋白特异性材料特性（胶原纤维的卷曲角度和弹性模量）。
对从幼年树鼩获取的巩膜条带进行拉伸试验，这些树鼩暴露于三种不同视觉条件下：正常、单眼佩戴-5 D镜片以诱导近视以及恢复阶段。胶原纤维在未加载的巩膜中呈卷曲状，随着组织在负载下变硬而展开。使用基于微观结构的本构模型进行反向数值分析，以估计胶原纤维的（未加载）卷曲角度和弹性模量。
与对照眼相比，处理眼在佩戴镜片2天后卷曲角度显著更高，并且在佩戴镜片直至21天期间一直显著更高（P < 0.05）。在恢复过程中，处理眼和对照眼卷曲角度的差异随着眼轴伸长率的变化迅速消失。在开始和停止佩戴镜片后，两只眼睛的弹性模量均迅速且大幅增加。
估计的巩膜胶原纤维卷曲变化在时间上与近视发展和恢复过程中眼轴伸长率的变化相关。这一发现表明，眼轴伸长可能受一种调节胶原纤维卷曲的重塑机制控制。观察到的巩膜硬度的双眼变化在时间上与眼轴伸长率无关，表明巩膜变硬可能与近视没有因果关系。
