Age-related changes in the absorption characteristics of the primate lens

PURPOSE. To quantitate aging of the primate lens by changes in the absorpti on characteristics that are related to the yellowing of lens protein. METHODS. The lenses of lower primates and humans were sectioned anterior to posterior every 0.25 mm, and the UV-visible spectrum of each section was m easured to determine die cumulative spectra along the visual axis. The rati o of the absorbance at 320 nm (formed with aging) to the absorbance at 365 nm (present in the young lens) was correlated with the age of the lens. RESULTS. In the young primate W-B is transmitted to the retina, and W-A is transmitted to the nucleus of the lens. By puberty, changes in the absorpti on characteristics of die lens that are associated with the yellowing of le ns protein prevented most of the W-B front reaching the retina and by the e ighth decade, the transmittances at 320 and 365 nm to the nucleus of the le ns were approximately 40% and 79%, respectively. A linear relationship betw een the ratio of absorbance It 320 to 365 nn and age was found for both low er primates and humans to the age of 80 years, This is surprising, because the maximum life span of the tower primate is approximately 35 years, where as humans may live 100 years. CONCLUSIONS, These data suggest that the observed spectral changes associat ed with the yellowing of the lens are the result of a chronological process . such as chemical or photochemical modifications, not biological aging.