The photoreceptor cells essential for colour vision and high acuity vision, present in large numbers in the fovea. In the human eye there are three types of cones, differentially sensitive to particular wavelengths of light depending on the opsin variant expressed. The first is most sensitive at long wavelengths (564–580 nm, yellow), the second to medium wavelengths (534–545 nm, green), and the third to shorter wavelengths (420–440 nm, violet). Neural processing allows a full spectrum of colours to be perceived. See colour blindness; compare retinal rod.
Subjects: Medicine and Health.