Spectral properties of the anterior segment of primates

Purpose To determine the age related spectral properties of the anterior segment such as transmission and fluorescence and relate those changes to aging mechanisms and retinal imaging Methods A simple method has been developed to determine the optical properties of the anterior segment of the intact eye. This consists of a probe which is inserted into the posterior sclera and detects light passing through the anterior segment. The probe is connected to a CCD spectrophotometer via a fiber optic bundle. Using this the absorptive properties of primate cadaver eyes were determined Results A young primate anterior segment has a maximum absorption of 365 nm due to the beta‐glucoside of 3‐hydroxykynurenine (3‐HKG) in the lens. This has a small transmission window to the retina centered at 320 nm, which closes up at around puberty. There is also a steep increase in transmission at wavelengths longer than 400 nm. With aging there is an increase in absorption throughout the visible (up to 550 nm)such that by the 6th decade only 20% of blue light is transmitted to the retina compared to the young primate eye. The increase in absorption is paralleled by an increase in fluorescence. Conclusion Yellowing of the lens seems to be related to reactions of 3‐HKG. The window of transmission at 320 nm in the young primate may explain the early increased rate of production of lipofuscin in the retina. The rate of lenticular yellowing is similar to the rate of lipofuscin formation in the retina from 20‐70 years, suggesting that the amount of light absorbed by lipofuscin is constant over that span. The role of age related lenticular changes in retinal imaging will be discussed.