Of the five senses, vision is one of the most useful. Not only does it allow a person to experience the color and form of the environment, but it allows for the recognition of approaching dangers. The ability to see is manifested by the specialized parts of the eye in conjunction with specific areas of the brain. The eye functions in many ways to produce images that enhance, assist and alert.
Light Refraction
Light enters the eye and is refracted by the cornea and lens. Refraction bends the stream of light directly onto the retina, an area of the eye that begins the process of seeing. The cornea is a clear, dome-shaped structure on the front of the eye. When light hits the eye, the cornea bends, or refracts the light onto the lens. The lens further refracts the light onto the retina. With aging cataracts can form on the lens, which are a clouding of the lens that decreases visibility, according to Washington University School of Medicine and the University of Miami.
Light Attenuation
The amount of light entering the eye must be controlled, or attenuated, to maintain focus and to protect the structures of the eye from harmful ultraviolet rays. The pupil, or dark center of the eye, opens and closes to control the entrance of light. The iris, or colored portion of the eye, surrounds the pupil and contains small muscles that contract and relax to control the amount of light that can enter the pupil, according to the University of Michigan.
Light Detection
The retina is located at the back of the eye and contains photosensors that detect light signals and send that information to areas of the brain specialized to produce visual images. The photosensors, including rods and cones, transmit electrical nerve signals to the brain via the optic nerve. Damage to the photosensors, particularly in the fovea, or center of the retina, cause blindness, according to the University of Utah.
Eye Movement
The eyes must move in order to focus light upon the retina to perceive the object of interest. An object is blurry if it is not looked at directly. The muscles of the eye function to move the eyes in all directions and are controlled by the oculomotor nerve. Types of eye movements include saccades, smooth pursuit, convergence and divergence, according to North Dakota State University.
