Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Laforja 88, 08021 Barcelona, Spain.
Philos Trans R Soc Lond B Biol Sci. 2011 Apr 27;366(1568):1278-92. doi: 10.1098/rstb.2010.0300.
Cataract is a visible opacity in the lens substance, which, when located on the visual axis, leads to visual loss. Age-related cataract is a cause of blindness on a global scale involving genetic and environmental influences. With ageing, lens proteins undergo non-enzymatic, post-translational modification and the accumulation of fluorescent chromophores, increasing susceptibility to oxidation and cross-linking and increased light-scatter. Because the human lens grows throughout life, the lens core is exposed for a longer period to such influences and the risk of oxidative damage increases in the fourth decade when a barrier to the transport of glutathione forms around the lens nucleus. Consequently, as the lens ages, its transparency falls and the nucleus becomes more rigid, resisting the change in shape necessary for accommodation. This is the basis of presbyopia. In some individuals, the steady accumulation of chromophores and complex, insoluble crystallin aggregates in the lens nucleus leads to the formation of a brown nuclear cataract. The process is homogeneous and the affected lens fibres retain their gross morphology. Cortical opacities are due to changes in membrane permeability and enzyme function and shear-stress damage to lens fibres with continued accommodative effort. Unlike nuclear cataract, progression is intermittent, stepwise and non-uniform.
白内障是晶状体物质中可见的不透明物，当位于视轴上时，会导致视力丧失。年龄相关性白内障是一种全球性的致盲原因，涉及遗传和环境影响。随着年龄的增长，晶状体蛋白会发生非酶促的翻译后修饰，以及荧光发色团的积累，从而增加氧化和交联的易感性，并增加光散射。由于人类晶状体在整个生命过程中不断生长，晶状体核心会更长时间地受到这些影响的影响，并且当第四十年在晶状体核周围形成谷胱甘肽转运的屏障时，氧化损伤的风险会增加。因此，随着晶状体的老化，其透明度下降，核变得更加坚硬，难以适应调节所需的形状。这就是老花眼的基础。在某些个体中，晶状体核中色素和复杂的不溶性晶状蛋白聚集体的稳定积累会导致棕色核性白内障的形成。该过程是均匀的，受影响的晶状体纤维保留其大体形态。皮质混浊是由于膜通透性和酶功能的改变以及在持续调节努力下对晶状体纤维的剪切应力损伤所致。与核性白内障不同，进展是间歇性的、逐步的和不均匀的。
