Changes in the lens appear by the age of 2 months in early aging OXYS rats, at the age of 6 months these changes are detected in 100% animals, and by 12 months both eyes are involved. According to biomicroscopy findings, predominant forms of cataract are vesicular, annular, and dendritic, located in the cortical layer and/or nucleus of the lens. Light and electron microscopy showed morphological changes involving all structural components of the lens: epithelial degeneration progressing with age, deformation of fiber architectonics, and appearance of uneven condensations. Cataract in OXYS rats corresponds to senile cataract, which makes this rat strain a unique model for studies of the pathogenesis of involutive cataract and elaboration of methods for its prevention and correction.