The inherent, age-dependent loss of retinal ganglion cells is related to the lifespan of the species.

Retinal ganglion cells are neurons that transmit visual information from the retina to the brain. With age, there is an inherent loss of retinal ganglion cells that we have quantitated by retrograde labeling of these neurons. In adult mice, the loss of retinal ganglion cells is approximately 2.3% per month; in adult rats, the loss of retinal ganglion cells is approximately 1.5% per month. The total losses of these neurons over the average lifespans of mice and rats are similar to those which have been reported in monkeys and humans. Furthermore, caloric restriction, which extends the lifespans of mice and rats, slows the temporal age-related loss of retinal ganglion cells. Thus, the total age-dependent losses of these neurons appear to be approximately the same over the lifespans of these mammalian species.