Quantification of loss of retinal ganglion cells. The percent survival of retinal ganglion cells following optic nerve crush (ONC) is shown for two strains of mice, C57BL/6J (B6) and DBA/2J (D2). The data points represent the percent survival for each of the retinas that received a crush of the optic nerve. The means of each group are indicated by the horizontal lines. This number was calculated by dividing the density of NeuN-positive cells optic nerve crush retinas by the average density of the control retinas of the same strain. There was a statistically significant (t-test, p < 0.01) difference in the survival of NeuN-positive cells, with 54% survival in the C57BL/6J mouse and 62% survival in the DBA/2J mouse.