Retina is a light-sensitive layer that lines the interior of the eye. It is composed of light-sensitive cells known as rods and cones. The human eye contains about 125 million rods, which are necessary for seeing in dim light. Cones, on the other hand, function best in bright light.
There are between 6 and 7 million cones in the eye and they are essential for receiving a sharp accurate image and for distinguishing colors. The retina works much in the same way as film in a camera.