Retinal anatomy: Comparison of primate (including human) and mouse retina

This review summarizes our current knowledge of the anatomy of the primate (including human) retina. Understanding the structure and function of the primate retina has become an important scientific goal both for basic and clinical sciences, as in recent decades, noninvasive anatomic (high resolution confocal and optical coherence tomography) and functional (electroretinogram (ERG) and related) methods are increasingly used to study retinal diseases in humans. Further, the development of molecular-based methods has revealed deep homologies in retinal cell types across vertebrate orders, which gives new relevance to mouse models for blinding diseases. Here, the morphology, connectivity, and functional role of the major cell classes: rod and cone photoreceptors, horizontal, bipolar, Müller, amacrine, and ganglion cells are described. The focus is on the primate retina, which contains at least 12 types of bipolar cells, at least 26 types of amacrines (with only 6 types well understood), and at least 17 types of ganglion cells. In the mouse retina, the number of bipolar types is comparable to that in primates, but the number of amacrine (over 60 types) and ganglion (over 30 types) cell types is significantly higher, indicating a reduction in the number of retinal pathways in primates. Other important features found in primate retinas (but absent from mouse retinas) include a fovea, which is essential for high acuity vision, and the presence of three types of cones enabling trichromatic color vision.