Light perception is the process by which an organism or man-made device perceives and interprets light from the environment. For this to occur, light must first reach some form of organ or device that can receive visual input, such as the eyes possessed by many organisms. When the light strikes the light-receiving organ or device, some form of processing, as by the brain or a computerized system, occurs to turn the sensory input into meaningful perception. In some cases, light perception by the organism or device may only provide information regarding whether or not there is light. In other cases, as in the case of human perception, light provides detailed information about the external environment in the form of colors, spatial data, and well-defined shapes.
The first part of light perception occurs when light from some source interacts with a sensory organ, such as the human eye. The human eye, as well as many other types of organic and artificial sensory apparatuses, can focus on particular environmental features, thereby engaging in selective light perception. The raw sensory input is converted to neural impulses in the case of human and animal vision or to electrical signals for computerized visual devices. Organs or devices capable of receiving sensory input are not capable of perception on their own, as perception requires the sensory input to be processed.
Neural or electrical impulses are interpreted by the brain which, in humans, produces a detailed representation of the external environment. This processing presents an interesting problem to psychologists, cognitive scientists, and even philosophers. Neural processing is a necessary intermediary between the outside world and human light perception, so people do not actually see an exact replication of the world as it objectively is. How, exactly, neural processing affects light perception and how the perceived world varies from the "world in itself" is not known.
A wide range of different human diseases and disorders have a deleterious effect on light perception. Any direct damage to the eyes or to the parts of the brain responsible for processing of visual stimuli, for example, can greatly impair or even completely disable light perception. Likewise, some people are unable to perceive certain colors or any color at all while others are born completely blind. Additionally, diseases and disorders such as cataracts, glaucoma, and diabetic retinopathy can all lead to impaired vision. A variety of treatments and therapies — even neural implants — have been developed to combat such perception-based problems.