Variations in fluorescence characteristics of intact human crystalline lens segments as a function of age

Fluorescence spectra of human lenses were examined as a function of age. The relative intensity in the blue-green area was red shifted with age. Absorption and scatter produce a substantial contribution to this shift. Some change, however, was the result of a true fluorescence intensity shift. In the lower blue region a true independent red shift was found in the nucleus, but not in the cortex. In the upper blue region, true red shift in the nucleus was not significant with fluorescence excited at 400 nm but was significant with fluorescence excited at 375 nm; the shift was well defined in the cortex. This pattern is consistent with age-related accumulation of multiple fluorogens or fluorogen precursors in the lens with relative concentration differences in nucleus and cortex.