Intensity and polarization of light scattered at small angles from the human fovea.

We have investigated the equivalent reflectance and the degree of preservation of polarization of light scattered at the human fundus in vivo. Measurements are performed at various angles of incidence and reflectance with both a bleached and unbleached state of the visual pigment. In the light that is scattered from the fovea two components were distinguished. First, a wide angle scattered component whose behavior in terms of equivalent reflectance and degree of polarization is independent of the angle of incidence and reflectance. Also, its reflectance is only moderately affected by the density of the visual pigment. Second, a directional component that is most prominent in a bleached state of the visual pigment and with a central position of the entrance and exit light path. The degree of preservation of polarization is about 90% at short wavelengths and decreases to about 40% for red light. Polarization is almost invariant for the angle of incidence and reflectance and the density of the visual pigment. To explain the results a model is proposed in which the scattering of both components is assumed to take place at the same layer. A consequence of this model is that a significant amount of light leaks between the receptor outer segments.