Histologic changes of optic nerve after posterior ischemic optic neuropathy (PION). Posterior optic nerves appear normal 3 days after sham control surgical procedures (laser only/no erythrosin B) (A and D). B, However, 3 days after PION, an area of tissue edema is present. C, Atrophy and degenerative changes appear in posterior optic nerves 2 weeks after PION induction. E, Higher magnification of the boxed region in part B reveals swollen cells and caverns (arrows) within the edema area. F, Higher magnification of the boxed region in part C shows marked degeneration of neural tissue in the infarct region, producing an appearance resembling cavernous degeneration (arrow). Scale bars=100 μm.