One of the most e?ective ways of characterizing neural function is the evaluation of neural response of a particular stimulus. The neural response is typically assessed by the variation of spatio-temporal characteristics of on-screen stimulus while the excitation of neural system is initiated by interactions of light and photoreceptors. Therefore, we should consider distribution of light intensity on the retinal surface as stimulus for sensory signals to achieve an accurate estimation of neural function. Human eye, like every optical system, has aberration and di?raction e?ects that a?ects modulation transfer function. As a consequence, some variations in the resolution of reconstructed image on the surface of retina are inevitable rather than on screen stimulus. In this project we tried to ?nd out illumination of reconstructed image on the surface of retina by simulation of human eye as an optical system. As we need a proper model, ?rst, we consider di?erent schematic eyes. Next, the optical design software (Zemax, USA) was used for designing and ray tracing. Illuminance distribution of retinal image, while is related to patterns of irradiation illusion was simulated by ray tracing technique. Our simulation for irradiation illusion shows an extension of edges in the central white square (in On-Center pattern) in comparison to the central dark square (in O?-Center pattern).