OBJECTIVE To describe a patient who developed unilateral shock-induced anterior ischemic optic neuropathy (SIAION) after gastrointestinal hemorrhage followed by presumed idiopathic nonarteritic anterior ischemic optic neuropathy (NAION) in the fellow eye. METHODS Retrospective, observational case report and literature review. METHODS The case history of an 80-year-old man who developed SIAION, followed by NAION in the fellow eye, was reviewed. All previously reported cases of SIAION were reviewed. METHODS Neuro-ophthalmic examination, including visual acuity, funduscopy, and automated perimetry. RESULTS An 80-year-old man, with a history of gastrointestinal bleeding from a duodenal ulcer, was hospitalized and received four units of packed red blood cells after he was found to be severely anemic (hemoglobin 6.7 g/dl). Three days later he complained of loss of vision of the right eye. Neuro-ophthalmic examination 2 weeks later disclosed a visual acuity of counting fingers at 6 inches in the right eye and 20/40 in the left eye, with a right relative afferent pupillary defect and a superior altitudinal visual field defect. Funduscopy revealed optic disc edema with a temporal parapapillary hemorrhage in the right eye and a small optic disc, with no cup, in the left eye. A diagnosis of SIAION secondary to anemia was made. Six weeks later he developed a new inferior altitudinal visual field defect in the left eye and diffuse optic disc swelling. He had no signs or symptoms of giant cell arteritis or polymyalgia rheumatica, his hemoglobin at this time was 11.9 g/dl, and the Westergren erythrocyte sedimentation rate was 6 mm/hour. CONCLUSIONS Our patient developed optic disc swelling of the right eye after an episode of gastrointestinal hemorrhage (SIAION). The disc swelling in the left eye occurred 8 weeks later, when his hemoglobin had increased to 11.9 g/dl. The timing of the ischemic optic neuropathies suggests that the acute anemia led to involvement of the first but not the second eye. The configuration of the optic disc may have predisposed not only to the second event (NAION) but also to the first episode (SIAION).