It is here that light stimulus is changed into neuronal stimulation through photochemical processes. The center of the retina has a small groove. This is the macula which contains only cones and where vision is sharpest. This rod-free visual groove lies along the visual axis which is optically the midpoint of the retina. The cones here are clustered closely together over an area of 5 gmm and enable visual acuity as well as colour vision.
Rods cover the majority of the periphery and serve for vision in poor light and spacial awareness.
The light sensitive rods and cones are found deep within the retina and not on the surface.