The ratio of RGCs to Photoreceptors is the highest at the center of the human retina
The human and other primate retinas are characterized by a specialized central retinal region while the peripheral retina resembles the retina of other mammals. This central area is called the macula lutea and the central 1 mm of this area is the fovea centralis.
This central region of the primate retina is highly specialized and developmental mechanisms at the fovea are unique among mammalian retina. The central macula is different from peripheral retina in that rods are absent. Another significant difference is that neuronal composition of the macula favors neurons of the midget pathway, consisting of one cone that forms synapses with two bipolar cells which in turn make connections with two retinal ganglion cells (RGCs) forming a circuit that subserves high visual acuity and color vision. Because of the high ratio of RGC to cones, ~ 500’000 RGCs are located at the foveal rim, representing about one half of the whole population of RGCs in the human retina. The macula and fovea make human visual perception unique among mammals.
A good knowledge of the genetic network underlying the development and maintenance of this highly specialized region is required to address some of the crucial issues about age-related macular degeneration (AMD), glaucoma and other human retinopathies.
