Cataract pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Pathophysiology
The lens is composed of specialized proteins known as crystallins, having optical properties attributed to the fine arrangement of their three-dimensional structure and hydration. The membrane protein channels maintain osmotic and ionic balance across the lens, and the cytoskeleton provides for the specific shape of the lens cells, especially the fibre cells of the nucleus Protein-bound sulfhydryl (SH)-groups of the crystallins are protected against oxidation and cross-linking by high concentrations of reduced glutathione, thus maintaining its transparency. The molecular compositions, as well as tertiary and quaternary structures, provide a high spatial and timely stability principally of the larger crystallins, which are able to absorb shortwave visible light, ultraviolet and infrared radiation for longer durations while maintaining its transparency. This provides a substantial protective function for the activity of various enzymes of the carbohydrate metabolism. As the person ages, the oxidative stress leads to an imbalance between the systemic manifestation of reactive oxygen species and the crystalline lens' ability to detoxify the reactive intermediates or to repair the resulting damage. The disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including proteins, lipids, and DNA.