Point-spread function for light scattered in the human ocular fundus.

A model based on the framework of fundal reflectance model III is developed for the lateral spreading of light that emerges from the human ocular fundus after scattering in the choriocapillaris and the choroidal stroma. Blood in these layers is modeled as a forward scatterer, and the Kubelka-Munk diffuse radiation environment used for the choroid in model III is replaced by an arrangement of embedded reflectors that gives the same remittance. An equation is derived for the point-spread function, and sample calculations illustrate the dependence of the spreading function on retinal site and wavelength and identify the characteristic influences of the long-wavelength edge of the 575-nm oxyhemoglobin absorption band and the choroidal melanin.