A molecular model for age-related cataract formation in the lens. Environmental stresses could lead to covalent damage, such as deamidation or photo-oxidation, to the crystallins. This damage could destabilize γ-crystallins, which are otherwise very stable, populating aggregation-prone species (I*). α-crystallin would sequester such species in younger individuals (green arrow). But as we age, the finite levels of free α-crystallin in the mature lens fibers will be diminished leading to aggregation (orange arrows).