EFFECTS OF AGING ON THE DENSITIES, NUMBERS, AND SIZES OF RETINAL GANGLION-CELLS IN RHESUS-MONKEY

We used stereological procedures that yield unbiased estimates to quan tify the densities, numbers, and soma sizes of retinal ganglion cells in seven young adult and six old rhesus monkeys. The retinae were flat mounted so that we could determine whether there are different aging- related losses in different retinal regions. The mean (+/- standard de viation) fetal number of ganglion cells was 1,529,039 +/- 115,260 in y oung-adult retinae and 1,556,698 +/- 165,056 in old retinae, a differe nce that was nor statistically significant. There also were no signifi cant differences between young and old retinae in the densities or tot al numbers of ganglion cells in the four retinal quadrants, in four co ncentric retinal zones from fovea to peripheral retina, or in smaller hemiretinal regions of the concentric zones. Ganglion-cell soma sizes also did not differ significantly between young and old animals. Moreo ver, counts of the largest ganglion cells, which probably correspond t o P alpha ganglion cells, revealed no selective loss of these cells wi th aging. These results are consistent with our previous anatomical an d physiological studies of the LGN. Together they suggest that the ret ino-geniculate pathways are relatively unaffected by aging in the rhes us monkey.