Optic neuritis and transient visual disturbances are common and challenging neuro-ophthalmic problems. Optic neuritis may occur during the course of several neurologic and systemic disorders and is characterized by reversible central visual loss. In many patients, signs and symptoms of multiple sclerosis occur after an episode of optic neuritis. Although several risk factors for development of multiple sclerosis have been identified, the relationship between optic neuritis and multiple sclerosis is still controversial. Transient visual disturbances may take the form of visual loss or visual hallucinations. In many cases, the cause of transient visual loss is never found. Hallucinations of ocular origin, however, are easily diagnosed by a thorough eye examination.