retinal cone
any of various photoreceptors in the retina that require moderate to bright light for activation, as opposed to retinal rods, which require very little light for activation. In primates, retinal cones are concentrated in the fovea centralis of the retina, where their high spatial density and the pattern of connections within their pathways are critical for high-acuity vision. The cone pathways also provide information about the color of stimuli. This is achieved by the presence of three different populations of cones, each having their maximum sensitivity to light in the short, middle, or long wavelengths of the spectrum, respectively. Other animals have additional populations of cones; for example, some fish have cones that are sensitive to ultraviolet wavelengths. See also photopic vision; photopigment.