Localization of papillofoveal bundles in primates

Axons in the fovea are precisely organized to ensure accurate vision. We investigated the morphologic characteristics and localization of nerve bundles in the optic nerve in primates. Macaque eyes were studied for conventional and immunostaining, and also marmoset eyes for carbocyanine dye tracing. Locally confined lesions associated with similar findings to human age-related macular degeneration (ARMD) were also evaluated. Axons of retinal ganglion cells formed fasciculi near their origin, and these fasciculi formed bundles thereafter. In the retinal nerve fiber layer, ascending bundles assembled stratification adding proximal bundle underneath successively. Bundles in the arcuate zone displayed a characteristic fine, parallel arrangement, whereas those in the outside zone intermingled with undefined reticular bundles as they approached the optic nerve head. Macular bundles remained in groups and were distributed in the temporal wedge of the optic nerve head. Orthograde and retrograde tracing revealed that these bundles formed confined groups of various sizes and, ultimately, a specific group of small bundles located in the innermost row, near the central vessels. In addition, these bundles showed evidence of focal degenerative deterioration in eyes with ARMD. Papillomacular bundles have a characteristic alignment and configuration. Foveal bundles that compose the confined group closest to the optic trunk (which we term papillofoveal bundles) appear to have functional significance with respect to the isolated lesions that accompany central vision loss or preservation.