Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, MO, USA.
Philos Trans R Soc Lond B Biol Sci. 2011 Apr 27;366(1568):1250-64. doi: 10.1098/rstb.2010.0302.
The purpose of the lens is to project a sharply focused, undistorted image of the visual surround onto the neural retina. The first pre-requisite, therefore, is that the tissue should be transparent. Despite the presence of remarkably high levels of protein, the lens cytosol remains transparent as a result of short-range-order interactions between the proteins. At a cellular level, the programmed elimination of nuclei and other light-scattering organelles from cells located within the pupillary space contributes directly to tissue transparency. Scattering at the cell borders is minimized by the close apposition of lens fibre cells facilitated by a plethora of adhesive proteins, some expressed only in the lens. Similarly, refractive index matching between lens membranes and cytosol is believed to minimize scatter. Refractive index matching between the cytoplasm of adjacent cells is achieved through the formation of cellular fusions that allow the intermingling of proteins. Together, these structural adaptations serve to minimize light scatter and enable this living, cellular structure to function as 'biological glass'.
晶状体的作用是将视觉环境的清晰、无失真图像投影到神经视网膜上。因此，首要的前提条件是组织必须是透明的。尽管蛋白质含量非常高，但由于蛋白质之间的短程有序相互作用，晶状体胞质仍然是透明的。在细胞水平上，瞳孔空间内的细胞程序性地消除细胞核和其他光散射细胞器，这直接有助于组织透明。通过大量仅在晶状体中表达的黏附蛋白，使晶状体纤维细胞紧密贴合，从而将细胞边界处的散射降至最低。晶状体膜和胞质之间的折射率匹配被认为可以最大程度地减少散射。通过形成允许蛋白质混合的细胞融合，实现相邻细胞的细胞质之间的折射率匹配。这些结构上的适应性共同作用，最大限度地减少光散射，使这个有生命的、细胞结构能够像“生物玻璃”一样发挥作用。
