Cones

Cones are the second type of photoreceptor occurring in
the retina of the human eye. They are conical in shape and
are associated with colour vision and perception of fine
detail. Shorter and far fewer than the eye’s rods, cones are
less sensitive to low illumination levels and are mediators
of photopic rather than scotopic (Greek skotos, “dark”)
vision. Cones are mostly concentrated within the central
retina (macula), which contains the fovea (depression in
the retina), where no rods are present. In contrast, the
outer edges of the retina contain few cones and many rods.
Chemical changes that occur when light strikes the cones are ultimately relayed as impulses to optic nerve fibres
that enter the brain.