Chapter 1 - Formation and Sampling of the Retinal Image

Abstract

Vision begins with the formation of an optical image of the external world upon the retinal mosaic of light-sensitive photoreceptors. Because image formation is the very first step in the visual process, imperfections in the eye's optical apparatus have the potential for affecting every aspect of visual perception, from color to motion, space, and form. Even if the focusing components of the eye's optical system were perfect, the retinal image would still be degraded by the diffraction of light as it passes through the pupil. Another potential limiting factor for vision is the scattering of light as it traverses the ocular media and retina before being absorbed by the visual pigment molecules inside photoreceptors. Thus, the study of visual perception must logically begin with the imaging properties of the eye to uncover those optical factors that constrain the quality of vision. This chapter aims to succinctly review current understanding of the formation and sampling of the retinal image in the human eye and the visual limitations imposed by these initial stages of the visual process. When taken together, this neuro-optical model of the eye provides a conceptual framework for interpreting empirical studies of the optical and sampling limits to visual perception and the impact these two factors have in daily life.