The retina is the light sensitive inner surface of the eye containing the receptor rods and cones, as well as many layers of neurons that begin the processing of visual information. The retina is an extension of the central nervous system that forms during embryonic development. This is one reason why scientists are interested in retinal processing; the retina is also an accessible part of the brain that can be easily stimulated with light. If it were possible to follow a ray of light as it enters the eye, one would see that the ray makes its way through the retina’s outer layer of cells to the buried receptor cells, the rods and cones. Light waves striking the rods and cones bring about chemical changes that generate neural signals. This correlates with the optic nerve, which is the nerve that carries neural

Light enters the eye through the cornea, a transport protector; it’s the clear bulging surface in front of the eye, and the main refractive surface of the eye. The cornea is normally transparent and uniformly thick, and its richly supplies with nerve fibers. It’s very sensitive to foreign bodies, cold air, and chemical irritations. It then passes through the pupil, the adjustable opening in the center of the eye through which light enters. The pupil diameter ranges from about three to seven millimeters. The sphincter muscle constricts or dilates the pupil. The iris, a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening, regulates the amount of light. The iris is highly pigmented and has a remarkable ability to adjust light intake by dilating and constricting in response to light intensity and even to inner emotions.

Behind the pupil is a lens that focuses the incoming rays into an image on the light sensitive back surface. It is the transparent structure behind the pupil that changes shape to focus images on the retina. Made up of proteins and water, the lens consists of

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, rods cones, optic nerve, blind spot, light enters, vision light, changes shape focus, light enters eye, vision light rays, vision normal vision, light sensitive, change shape, farsighted vision, objects focus, surface eye,