The distribution of
ganglion cells in the mouse retina was studied with the use of Nissl criteria for distinguishing cell types in the
ganglion cell layer. Retrograde filling with
horseradish peroxidase (HRP) from the optic fiber tract helped to validate Nissl criteria and served to identify displaced
ganglion cells. We estimated a total of 117,000 nonvascular cells in the
ganglion cell layer; of these, 70,000 were probably
ganglion cells, and 47,000 could not be classified. The density of the presumed
ganglion cells was highest-more than 8000 cells/mm2-just temporal to the optic disk, and lowest-less than 2000 cells/mm2-in the most dorsal retina. The
retinal region with highest
ganglion cell density was slightly elongated in a nasotemporal direction. About 2% of all HRP-filled
ganglion cells had their cell bodies in the inner nuclear layer. These displaced cells differed in topographical distribution from the normally positioned
ganglion cells: although occurring throughout the retina, they were more common along the
retinal periphery. Measurements of
ganglion cell areas showed a tendency toward larger size with eccentricity. At no
retinal location did cell-size histograms reveal clearly separate size classes.