Ischemic optic neuropathy. ION typically affects the older population with a sudden decrease in vision, altitudinal visual field loss, and a swollen optic nervehead. Systemic hypertension and diabetes mellitus are the most commonly associated medical problems. Occlusion of the posterior ciliary arterial blood supply to the retrolaminar optic nerve leads to axoplasmic stasis and further compromise of vessels in the nerve substance, which causes the typical funduscopic appearance. Although there is no recognized medical treatment that can reverse the visual loss, a recent report suggests optic nerve sheath decompression for a select group of patients with a gradual decline in vision due to ION may be beneficial. When ION occurs in persons less than 50 years of age, such etiologies as juvenile diabetes mellitus, antiphospholipid antibody-associated clotting disorders, collagen-vascular disease, and migraines should be considered. Rarely, complications of intraocular surgery or acute blood loss may cause an ischemic event in the optic nerve. 