Grytz Rafael, El Hamdaoui Mustapha
Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
J Elast. 2017 Dec;129(1-2):171-195. doi: 10.1007/s10659-016-9603-4. Epub 2016 Oct 24.
The sclera uses unknown mechanisms to match the eye's axial length to its optics during development, producing eyes with good focus (emmetropia). A myopic eye is too long for its own optics. We propose a multi-scale computational model to simulate eye development based on the assumption that scleral growth is controlled by genetic factors while scleral remodeling is driven by genetic factors and the eye's refractive error. We define growth as a mechanism that changes the tissue volume and mass while remodeling involves internal micro-deformations that are volume-preserving at the macroscale. The model was fitted against longitudinal refractive measurements in tree shrews of different ages and exposed to three different visual conditions: (i) normal development; (ii) negative lens wear to induce myopia; and (iii) recovery from myopia by removing the negative lens. The model was able to replicate the age- and vision-dependent response of the tree shrew experiments. Scleral growth ceased at younger age than scleral remodeling. The remodeling rate decreased as the eye emmetropized but increased at any age when a negative lens was put on. The predictive power of the model was investigated by calculating the susceptibility to scleral remodeling and the response to form deprivation myopia in tree shrews. Both predictions were in good agreement with experimental data that were not used to fit the model. We propose the first model that distinguishes scleral growth from remodeling. The good agreement of our results with experimental data supports the notion that scleral growth and scleral remodeling are two independently controlled mechanisms during eye development.
巩膜在发育过程中通过未知机制使眼球的眼轴长度与其光学结构相匹配，从而形成具有良好聚焦能力的眼睛（正视眼）。近视眼的眼轴长度相对于其自身的光学结构来说过长。我们提出了一个多尺度计算模型来模拟眼球发育，其假设为巩膜生长受遗传因素控制，而巩膜重塑则由遗传因素和眼睛的屈光不正驱动。我们将生长定义为一种改变组织体积和质量的机制，而重塑则涉及内部微观变形，这些变形在宏观尺度上保持体积不变。该模型根据不同年龄的树鼩在三种不同视觉条件下的纵向屈光测量数据进行拟合：（i）正常发育；（ii）佩戴负透镜以诱发近视；（iii）摘除负透镜从近视状态恢复。该模型能够复制树鼩实验中与年龄和视力相关的反应。巩膜生长比巩膜重塑在更年轻的年龄就停止了。重塑速率随着眼睛趋于正视而降低，但在任何年龄佩戴负透镜时都会增加。通过计算树鼩对巩膜重塑的易感性以及对形觉剥夺性近视的反应，研究了该模型的预测能力。这两种预测结果都与未用于模型拟合的实验数据高度吻合。我们提出了第一个区分巩膜生长和重塑的模型。我们的结果与实验数据的良好一致性支持了这样一种观点，即巩膜生长和巩膜重塑是眼球发育过程中两个独立控制的机制。
