Approach to optic neuropathies: clinical update. 
Visual loss is a common symptom brought to the attention of the practicing neurologist.  In this circumstance, the proper identification of an optic neuropathy is critical.  Recognition of key clinical clues will permit the clinician to construct a likely differential diagnosis and pursue appropriate testing.  This review first addresses the elements of the history and examination which are most useful in evaluating a patient with visual loss, and then briefly discusses the main entities responsible for causing unilateral and bilateral optic neuropathies.