Light scattering of normal human lens. III. Relationship between forward and back scatter of whole excised lenses

Twenty-three human lenses from age 3-76 years were studied. Lenses obtained 24-36 post-mortem were exposed to monochromatic light (435.8 and 546.1 nm) in the I parallel and I+ modes and to white (tungsten lamp) unpolarized radiation. The light scattering intensities were obtained as a function of scattering angles from 0 to 135 degrees. The scattering intensities in the forward directions are greater than in the back scatter in all modes of illuminations. The age dependence of a number of light scattering parameters such as percent transmission; I theta/Io; dissymmetry and depolarization were obtained using regression analysis. These parameters may serve as standards of normal lenses to which similar parameters of cataractous lenses can be compared. Relationships between back scatter and forward scatter have been established using the regression coefficients. Thus, the light scattering intensity observed in the slit lamp (at 135 degrees back scatter) can be quantitatively related to the light reaching the retina at different angular displacements.