The two types of light-sensitive cells of the retina are rods and cones. Named because of their cylindrical shape, rods are interspersed throughout the retina. They are highly sensitive to low light and shadow and allow for at least some degree of nighttime vision. Cones are present throughout the retina also, but are very highly concentrated in the fovea of the macula. Different cones are sensitive to different wavelengths and allow one to see vivid colors and sharp detail in conditions of bright light. There are 20 times more rods than cones.
Rods and Cones