Abstract
Compound systems are generally treated by geometrical optics, for instance, through the Gauss' formalism. The objective is to simplify the process of image formation. However, this formalism does not include the wave characteristics of light and boundary effects. The treatment of diffraction is not straightforward. Thus, the extension of this formalism towards the scalar theory of diffraction is very desired. This work offers this extension and emphasizes its importance. Compound systems, including the human eye, are then modeled by Fresnel theory. For illustration, a lens-based model of the Fresnel transform is used to treat the human eye system.