Optic neuropathies for the neurologist

Before embarking on expensive ancillary testing, it is crucial for the neur ologist to distinguish visual loss due to optic nerve dysfunction from othe r causes of visual loss, This can usually be accomplished based on specific features of the history and bedside examination. Once it has been establis hed that a patient has some form of optic neuropathy, several clinical feat ures are helpful in determining the etiology. The most important of these i s the time course. Other factors include presence or absence of pain, patte rn of visual loss (particularly visual field defects), and funduscopic appe arance. In most cases, by using this information it is possible to differen tiate among the common forms of optic neuropathy: papilledema, ischemic opt ic neuropathy, optic neuritis, compressive lesions, toxic/nutritional defic iencies, and hereditary forms. This article also reviews recent information concerning the evaluation and treatment of optic neuritis, how to recogniz e conditions that mimic optic neuritis (e.g., neuroretinitis, papillophlebi tis), distinguishing arteritic from nonarteritic AION, and new developments in the genetics of Leber's Hereditary Optic Neuropathy. There is also a di scussion of various forms of toxic/nutritional visual loss including Cuban Epidemic Optic Neuropathy and visual loss due to commonly prescribed medica tions.