The retina is the light sensitive neural layer that lines the posterior internal portion of the eye. Two of its three types of photoreceptor cells, rods and cones, receive light and transform it into image-forming signals which are transmitted through the optic nerve to the brain. The retina, indeed an extension of the brain, takes light and turns it into chemical energy in turn into nerve impulses sent to the higher regions of the brain via the optic nerve. The optic nerve performs as a central tract connecting the retina to the brain. The long fibers that pass from the nerve cells in the retina comprise the optic nerve. The cones mediate color vision, the rods mediate light intensity. Hence, any change or damage to the retinal structure can interfere with vision. The blood vessels in the retina maintain an extremely unique structure.
The retina has ten distinct layers. One of its structures is an area called the optic disc which is sometimes referred to as "the blind spot". The reason is that the optic disc lacks photoreceptors. At the retina's center is an area called the fovea, a pit that is most sensitive to light and is responsible for our sharp central vision. The macula is a small area in the retina that contains special light sensitive cells which allow us to visualize fine detail clearly. The retina does not simply send a picture to the brain. The retina spatially encodes (compresses) the image to fit the limited capacity of the optic nerve.
There are many inherited and acquired diseases or disorders that may affect the retina. Some of them include Retinitis pigmentosa, Macular Degeneration, Cone-Rod Dystrophy (CORD), retinal separation, and Retinoblastoma. Treatment depends on the nature of the disease or disorder.
