Quantal and visual efficiency of fluorescence in the lens of the human eye

To document quantitatively the fluorescence in the human lens relevant to its interference with visual function. To explain quantitatively the experimental findings relative to loss of visual function. To study the relation between the fluorescence and the light transmission of the lens.

Three normal lenses, from 22-, 28-, and 69-year-old donors, were used. Fluorescent light was induced by a 4-mm diameter pencil beam of 380, 400, or 420 nm. It was measured as a function of the deflection angle from -10 to 150 degrees for different wavelengths.

The shapes of the emission spectra were comparable to those reported in the literature. Total quantal efficiency of fluorescence was between 5% for 69 years and 380 nm excitation and 0.4% for 22 years and 420 nm excitation. The forward intensity was less than the backward intensity because of secondary absorption.

Fluorescence of the lens causes light with wavelengths of 420 nm and lower to be much more visually effective. A marked homogeneous veil is added to the point spread function. The total increase in luminous efficiency was a factor 3 to 6 at 400 nm, and a factor 70 to 150 at 380 nm. For other visual effects (glare) the increase can be larger.