Purpose: To offer clinical evidence that deficiency of vitamin B12 may adversely affect the neuronal function of patients who also have the 14,484 mitochondrial DNA mutation associated with Leber's hereditary optic neuropathy (LHON).
Methods: A case of a 27-year-old man with vitamin B12 deficiency and the 14,484 mitochondrial DNA mutation is presented and the literature on causes of some metabolic optic neuropathies reviewed.
Results: Visual loss and neurologic symptoms of vitamin B12 deficiency occurred together, at a time when the level of vitamin B12 was subnormal. Vision and other sensory functions began to improve within 2 months of vitamin therapy, and normal vision eventually was restored.
Conclusions: The relatively prompt improvement and the eventual complete recovery of vision following vitamin replacement therapy suggest that the subnormal level of vitamin B12 precipitated visual loss. Given the clinical similarities of subnormal vitamin B12, LHON, and nutritional/tobacco amblyopia, deficiency of adenosine triphosphate might be a unifying etiology for several types of optic neuropathy. This energy hypothesis provides a theoretical basis for the enigmatic phenomena of centrocecal scotomata and recovery of visual function after prolonged blindness.