Light scattering by donor lenses as a function of depth and wavelength.

PURPOSE To determine quantitatively dependence on the wavelength and angle, as a function of depth, of light scattering in the human lens. To compare the result for forward directions with psychophysical data. To derive candidate particle distributions that might be responsible for nuclear light scattering as significant in the psychophysical situation. METHODS The amount of light scattered by donor lenses (n = 15, ages 48 to 82 years) from a 1-mm x 0.1-mm white slit beam was measured as a function of depth in the lens for seven angles from 10 degrees to 165 degrees, and for four wavelengths from 400 to 700 nm. Absolute values for light scattering (Rayleigh ratios) were derived. RESULTS The light-scattering data are confounded by the short wavelength-absorbing pigments in the lens. After correction, backward light scattering in the nucleus followed wavelength to a power of -4. In the superior layers and for forward directions in the nucleus, light scattering was less dependent on wavelength. The nuclear data could be explained on the basis of a bimodal protein particle distribution: particles much smaller than wavelength, in quantitative accordance with the literature, and particles larger than wavelength, which control forward light scattering. CONCLUSIONS The particles of significance for forward light scattering have, on average, a mean radius of 692 nm and constitute only 0.000003 of the volume. The wavelength dependence of retinal stray light is lessened by: the large sizes, the contribution of superficial lenticular layers, the lenticular pigments, and the contribution of other components of the eye.