The photoreceptors of the eye are rod cells and cone cells. Their relative numbers in the retina are partly correlated with whether an animal is diurnal or nocturnal. The light absorbing molecule is retinal , synthesized from vitamin A, which is bonded to a characteristic kind of protein, opsin . Rod cells are sensitive to light but do not distinguish colors. Contains rhodopsin , which is inactivated by light.
Cone cells are responsible for daytime color vision.
Most dense at the fovea.