Ocular complications are common in the mitochondrial cytopathies and include optic atrophy and retinal degeneration. We retrospectively reviewed 80 patients with nonsyndromic mitochondrial cytopathies (ie, not Kearns-Sayre syndrome, myoclonus epilepsy associated with ragged red fibers [MERRF], mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes [MELAS], neuropathy ataxia and retinitis pigmentosa, Leigh disease, maternally inherited diabetes and deafness, and myoneurogastrointestinal disorder and encephalopathy) and found 10 cases of optic nerve hypoplasia. Optic nerve hypoplasia occurs in at least 12% of patients with nonsyndromic mitochondrial cytopathies. Although the exact pathogenesis of optic nerve hypoplasia in the context of mitochondrial cytopathy is unknown, we postulate that it is the result of excessive apoptosis during embryonic ganglion cell and/or axonal development from abnormal mitochondrial function and cellular energy metabolism.