The arrangement of land m cones in human and a primate retina

The relative numerosities and spatial arrangement of long-wave (L) and middle-wave (M) cones in the human and primate retina have long been debated. This topographical organization of cones is fundamental to the understanding of visual sensitivity and colour vision. This chapter examines the numerosity of L and M cones in the human fovea. It also examines cones at the ora serrata and analyzes the foveal array of a single female marmoset. The data suggests that the ratio of L:M cones in the foveal region in humans varies between individuals from close to unity to at least as high a 5L:M. However, the average for the population is 2:1. In the case of the female marmoset, the two types of long-wave cone were in the ratio 0.7:1. The functional significance of individual variation in the ratio of L and M cones in humans is discussed.