Nerve fiber layer of the macaque retina: retinotopic organization.

The transretinal pathway of optic nerve fibers in the retinas of cynomolgus and bonnet monkeys was studied by light microscopy following small intraretinal injections of horseradish peroxidase (HRP). Injections of HRP into nerve bundles at the optic disc labeled a few ectopic ganglion cells, in addition to those in the related retinal sector. Injections into nerve bundles in the retina labeled long (more than 3 mm) fibers of passage, most of which remained close to the vitreal surface as they crossed the retina. These long fibers mingled with short (less than 1 mm) peripapillary fibers at the disc margin and in the prelaminar part of the disc. Axons of intermediate ganglion cells (1-3 mm in length) were added to the fiber layer at its scleral border, beneath long fibers of more peripheral origin. These findings demonstrate a retinotopic organization of macaque nerve fiber bundles with long fibers vitreal and shorter fibers more scleral in position. Intermingling of fibers of disparate origin is extensive at the optic disc where a decussation of long and short fibers occurs.