A 29-year-old man developed vision loss in the right eye due to ophthalmic artery, cavernous sinus, and superior ophthalmic vein occlusion in mucormycosis. Diffusion MRI obtained within 2 days of symptom onset showed that the apparent diffusion coefficient values of the optic nerve and retina were remarkably decreased on the affected compared with the unaffected side. A follow-up MRI study 21 days after symptom onset revealed the anticipated disappearance of these signal changes, confirming that they were a true reflection of ischemia in the optic nerve and retina. This report adds to an accumulating body of literature on restricted diffusion in these tissues in conditions producing severe ischemia.