Physically essential to enabling sight, the photoreceptors on the retina of the eye which are responsive in low light conditions. see thumbnail to rightIn this illustration, the rods and cones are the pink forms shown embedded in the anterior of the retina's surface. The more uniformly thin rods, among the more thickly formed cones.Also see afterimage, binocular vision, gestalt, Op Art, ophthalmology, optical, optical mixing, perception, and peripheral vision.