ABSTRACT
In general, there are two classes of theoretical explanation for illusory distortions: structural theories and strategy theories. Structural theories propose that illusory distortions are based directly on the structural properties of the optical or neural systems. Strategy theories propose that illusions arise during the course of cognitive processing of the visual information. The first opportunity for the visual system to make contact with the external environment is through the dioptric system of the eye, which includes all the optically active components, which tend to bend or refract the light rays, as well as the optic media. Although chromatic and spherical aberrations are the major sources of image blurring in the eye; there is one other process that contributes to the degradation of the image. Light waves entering the eye are bent as they make contact with the edges of the pupillary aperture by the process of diffraction.
