Optic neuropathies for the neurologist.

Before embarking on expensive ancillary testing, it is crucial for the neurologist to distinguish visual loss due to optic nerve dysfunction from other causes of visual loss. This can usually be accomplished based on specific features of the history and bedside examination. Once it has been established that a patient has some form of optic neuropathy, several clinical features are helpful in determining the etiology. The most important of these is the time course. Other factors include presence or absence of pain, pattern of visual loss (particularly visual field defects), and funduscopic appearance. In most cases, by using this information it is possible to differentiate among the common forms of optic neuropathy: papilledema, ischemic optic neuropathy, optic neuritis, compressive lesions, toxic/nutritional deficiencies, and hereditary forms. This article also reviews recent information concerning the evaluation and treatment of optic neuritis, how to recognize conditions that mimic optic neuritis (e.g., neuroretinitis, papillophlebitis), distinguishing arteritic from non-arteritic AION, and new developments in the genetics of Leber's Hereditary Optic Neuropathy. There is also a discussion of various forms of toxic/nutritional visual loss including Cuban Epidemic Optic Neuropathy and visual loss due to commonly prescribed medications.