OPA1 and autosomal dominant optic atrophy: The two main forms of hereditary optic atrophy are Leber hereditary optic neuropathy (LHON), which is primarily caused by mutations in three mtDNA-encoded subunits of the mitochondrial respiratory complex I, and dominant optic atrophy (DOA), mainly attributable to mutations of the nuclear gene OPA1. These two pathologies present with incomplete penetrance and highly variable expressivity, suggesting that other genetic and/or environmental factors might influence the onset and the severity of the disease (Caporali et al., 2017).