Effects of optic nerve crush on the retinas of C57BL/6 and DBA/2J mice. The effect of optic nerve crush on the survival of retinal ganglion cells is shown in 4 panels. C57BL/6 retinas are shown in A (control) and B (optic nerve crush); DBA/2J retinas appear in C (control) and D (optic nerve crush). Note the significant decrease in ganglion cell staining after optic nerve crush. Ganglion cells were stained with NeuN. All panels are at 40× magnification. The scale bar in panel D represents 50 μm.