ABSTRACT
The vertebrate eye is a device that focuses an image onto an array of receptors and ultimately transmits some derivative of the visual information to the brain. Photoreceptors are oriented opposite in direction to those in the vertebrate eye; in octopus the tips of the photoreceptors point toward the pupil, whereas in all vertebrates photoreceptors point away from the pupil. Rods and cones exist, are widely distributed among vertebrates, and are usually related to vision under different conditions of lighting. In the normal vertebrate eye ultraviolet light, the short-wavelength radiation, is well filtered by the lens. Infrared rays can reach the retina. In the human eye, the two inner layers of the retina are nourished by the retinal circulation. Several developments have helped make intracellular recording in the retina possible. It is interesting that knowledge of retinal anatomy has been far ahead of its physiology.
