The Cone Photoreceptor Mosaic in Normal and Defective Color Vision

Abstract

Visual experience is initiated by photons captured in the photoreceptors. The arrangement of these photoreceptors—their topography—limits how we see and sets the stage for how the circuitry in the retina and brain operates. Four different classes of cells are interleaved in the photoreceptor layer of the retina: the rods and three spectral subtypes of cone that form the basis for trichromatic color vision, the long-, middle-, and short-wavelength-sensitive cones (L, M, and S, respectively). A great deal is understood about how the presence of three spectral cone types limits color perception; however, until recently, considerably less had been known about the spatial arrangement of these cone types and how their topography influenced visual experience. Recently, new methods have been developed that enable us to measure the spatial arrangement of cone photoreceptors in the living human eye. These new measurements have produced surprising results that answer some questions about color appearance but raise many others. In this chapter, we review the current understanding of the cone mosaic in normal and defective color vision, emphasizing recent results derived from adaptive optics retinal imaging.