 The visual system is the part of the central nervous system which gives organisms the ability to process visual detail, as well as enabling the formation of several non-image photo response functions. It detects and interprets information from visible light to build a representation of the surrounding environment. The visual system carries out a number of complex tasks, including the reception of light and the formation of monocular representations, the build-up of a nuclear binocular perception from a pair of two-dimensional projections, the identification and categorization of visual objects, assessing distances to and between objects, and guiding body movements in relation to the objects seen. The psychological process of visual information is known as visual perception, the lack of which is called blindness. Non-image-forming visual functions, independent of visual perception, include the pupillary light reflex PLR and circadian photoentrainment. This article mostly describes the visual system of mammals, humans in particular, although other higher animals have similar visual systems see bird vision, vision in fish, mollusci, and reptile vision.