Maximum cones are seen in: March 2005

Ans. B: Fovea centralis There are two basic types of retinal photo-receptors: Cones, responding to bright-light conditions, and Rods, responding to low-intensity light Depending on their spectral sensitivity, the former belong to either L (long-wavelengths sensitive), M (mid-wavelengths sensitive) or S (sho-wavelengths sensitive) cones. By combining their separate inputs, the brain creates colors. The cones are concentrated in the center of retina (fovea). Cones become larger up to about four times (of their size at fovea) toward outer areas of the retina. Fovea is the most sensitive pa of retina. It contains only cones and no rods. Since the fovea does not have rods, it is not sensitive to dim lights. Macula does not have a blood supply so the fovea receives oxygen from the vessels in the choroid.