Rod and Cone Responses in the Human Eye

Abstract

THERE is abundant evidence to show that the human eye has two distinct receptor mechanisms, one for vision in bright daylight and the other for vision at night. The sensitivity of the former, the photopic mechanism, is greatest for the longer wavelengths and is not much changed by dark adaptation. That of the scotopic mechanism is greatest for green and blue, and may be increased or reduced a thousand-fold by keeping the eye in darkness or light. From their distribution in the retina and in different animals, the cones are thought to be the photopic receptor organs and the rods the scotopic.