Functional diversity and clinical evaluation of retinal ganglion cells

Visual perception requires continuous, reliable communication from the eye to the brain. This is made possible by retinal ganglion cells (RGCs), whose axons comprise the optic nerve. Within the mammalian retina, ∼100 million photoreceptors capture photons of light reflected from the environment. Rather than acting as a "pixel detector" for reflected light, the retina performs significant neuronal computations across diverse circuits that selectively filter and encode information about distinct features of the visual scene. This visual feature detection culminates in approximately 1-1.5 million RGCs comprising ∼20 different types in primates. RGCs compute and transmit information about visual features to a variety of subcortical structures, where visual information is further processed and relayed to visual cortex. This review explores the basic physiology and anatomy of the retinal circuitry that underlies RGC processing in mammals, describing how vision scientists classify RGCs into distinct cell types, and summarizing the current understanding of feature detection by diverse RGC populations. We also review how electrophysiologic methods and/or imaging technologies are used for clinical evaluation of RGCs. Taken together, the information summarized in this review provides a detailed account of the known diversity of RGCs in the mammalian retina and their specific contributions to visual perception.