Efferent innervation of the retina

I Silver impregnation of the monkey's retina has been employed to study the presence and distribution of centrifugal fibers in flat mounts. This method has allowed identification of individual centrifugal fibers which appear to emerge from the optic papilla. Their course and distribution within the retina has been depicted. In the vicinity of the papilla, where the stained fibers in the optic nerve layer were very numerous, the centrifugal fibers could be differentiated from the ganglion cell axons by virtue of their thicker diameter, their irregular trajectory, and the presence of branches. By contrast in the mid and peripheral retina, the centrifugal fibers were readily identified. Successive bifurcations and a descending course toward the inner nuclear layer were characteristic features of intraretinal centrifugal fibers. Additional studies of vertical retinal sections have confirmed their descending trajectory from the optic nerve fiber layer to the innermost aspect of the inner nuclear layer. The findings in the monkey's retinas have been compared with the previous findings in human and other mammalian retinas using the same silver impregnation technique.