MT-ND4 and optic nerve disorder: Inherited optic neuropathies are intimately linked to mitochondrial function [6], with the majority of isolated (simplex) optic neuropathies connected to pathological variants in mitochondrial genes (most commonly MTND1, MTND4 or MTND6 in Leber hereditary optic neuropathy—LHON) [7] or autosomal genes regulating normal mitochondrial function (most commonly OPA1 in dominant optic atrophy—DOA) [7].