Wavelength dependence of the Stiles-Crawford effect explained by perception of backscattered light from the choroid

To explain the wavelength dependence of the directional sensitivity of huma n foveal cones (Stiles-Crawford I effect) we extended an existing fundus re flectance model for calculation of the total absorption by visual pigment. We took experimental data from literature for both the psychophysical and t he optical Stiles-Crawford effect and optimized parameters to fit the exper imental data. The wavelength dependence of the Stiles-Crawford effect could be well described with the geometrical optics model. Essential elements ar e self-screening and the inclusion of backscattered choroidal light for per ception. (C) 2001 Optical Society of America.