![]() The outer nuclear layer (ONL), composed of the cell bodies of the rods and cones, is about the same thickness in central and peripheral retina. Thus in central retina the cones are closely spaced and the rods fewer in number between the cones ( Figs. The inner nuclear and ganglion cell layers (INL, GCL) contain more cells, (more.)Ĭentral retina is cone-dominated retina whereas peripheral retina is rod-dominated. In central retina the inner and outer plexiform layers (IPL, OPL) are thicker than in peripheral retina. Different structure of central and peripheral human retina. The retinal message concerning the photic input and some preliminary organization of the visual image into several forms of sensation are transmitted to the brain from the spiking discharge pattern of the ganglion cells.įigure 10. Subsequently the absorbtion of photons by the visual pigment of the photoreceptors is translated into first a biochemical message and then an electrical message that can stimulate all the succeeding neurons of the retina. Light must, therefore, travel through the thickness of the retina before striking and activating the rods and cones ( Fig. A radial section of a portion of the retina reveals that the ganglion cells (the output neurons of the retina) lie innermost in the retina closest to the lens and front of the eye, and the photosensors (the rods and cones) lie outermost in the retina against the pigment epithelium and choroid. The optic nerve contains the ganglion cell axons running to the brain and, additionally, incoming blood vessels that open into the retina to vascularize the retinal layers and neurons ( Fig. The retina is approximately 0.5 mm thick and lines the back of the eye. The total retina is a circular disc of between 30 and 40 mm diameter ( 1-3). ![]() An animation from the iris to the retina.Ī circular field of approximately 6 mm around the fovea is considered the central retina while beyond this is peripheral retina stretching to the ora serrata, 21 mm from the center of the retina (fovea). ![]()
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