Spectroscopic Evaluation and Classification of the Normal, Aging, and Cataractous Lens. (With 1 color plate)

Abstract

Fluorescence, UV and visible and EPR spectroscopy studies were performed on normal human lenses ranging in age from 1 day to 92 years and on various cataractous lenses. These experiments revealed two specific age-related fluorescent compounds which develop in the lens nucleus on the basis of a UV-induced free radical tryptophan photo-degradation reaction resulting in an increasing concentration of the fluorogen with age. These fluorogens are responsible for the yellow color of the normal lens nucleus which becomes readily apparent by the second decade of life. The increase in the intensity of the yellow color with age parallels the increase in the 360 nm fluorogen concentration; the 435 nm fluorogen which appears to be a secondary product of the former, is related to the hazel to brown color which becomes manifest in the old lenses. The two fluorogens are markedly elevated in the nuclear (brown) cataracts but remain at normal or below normal levels in the cortical cataracts. A classification of the normal lens and primary cataracts is proposed on the basis of UV and visible light transmission and fluorescence spectroscopy in such lenses.