A diverse group of pathologic processes may affect the optic nerve. Clinical manifestations allow localization of pathology to the optic nerve and suggest possible etiologies. Optic disc edema and optic atrophy are fundoscopically visible signs of optic nerve pathology and may provide clues to the underlying process. Hereditary, toxic, nutritional, and compressive optic neuropathies often have characteristic clinical findings that may provide clues to a possible diagnosis.