Light passes through the cornea, pupil, and lens, where it is inverted and projected onto the retina. Specialized cells, called photoreceptors, comprise the retina. There are two kinds of photoreceptor cells in the mammalian retina: rod cells, which detect the relative intensity of light and operate best in darkness; and cones, which are color sensitive. When light strikes either of these cell varieties, they undergo a chemical reaction resulting in signals to the bipolar cells directly behind them.--->
Light information is conveyed as an electrical action potential through the neurons of the optic nerve.--->
The two tracts of the optic nerve — one from each eye — cross one another before they enter the brain. The right and left visual tracts coming from the eyes pass to the left and right hemispheres of the brain, respectively. A small bundle of neurons follows a separate visual pathway to convey information about light and dark to the neural regions that regulate the body's circadian rhythm, including sleeping and waking patterns. The majority of nerves in the visual pathway proceed to the thalamus in the mid-brain, where all visual information is sorted and then relayed to the cerebral cortex--->
The visual cortex is a very large region of the brain, occupying much of the occipital lobe. Here, many neurons are highly specialized to signal only when an object is seen with a specific color, angle, or location in the visual field of the eyes. The entire field of both eyes is represented in the cortex as a large map composed of these specialized cells arranged together, where the information conveyed by the visual pathway is sorted out and organized. Object recognition and the many complex aspects of conscious visual perception are distributed widely across the brain.