A metabolic optic neuropathy is caused by a spectrum of conditions affecting the optic nerve excluding trauma, ischemia, infection, immune or radiation.
Mechanism: Mitochondria appear to be the primary target.
Categories of metabolic optic neuropathy:
(1) heredodegenerative: Leber's hereditary optic neuropathy
(2) nutritional deficiency: vitamin B12 or folate deficiency
(3) toxic or drug-related: cyanide, ethambutol, styrene
Clinical manifestation:
(1) bilaterally symmetrical visual impairment
(2) loss of central visual acuity
(3) dyschromatopsia (blue/yellow, red/green or non-selective color defects)
(4) centrocecal visual field defect (horizontal oval visual field defect that includes the fixation point and blind spot)
(5) temporal optic disc atrophy
(6) specific loss of the nerve fiber layer in the papillmacular bundle
