Leber hereditary optic neuropathy is caused by mutations in mitochondrial genes, particularly, m.3460 G>A (MT-ND1), m.11778 G>A (MT-ND4), and m.14484T>C (MT-ND6), with m.11778 G>A being the most frequently reported mutation worldwide.6 These mutations affect complex I subunits of the mitochondrial respiratory chain, impairing mitochondrial function and increasing the levels of reactive oxygen species (ROS), resulting in selective loss of retinal ganglion cells (RGCs) and their axons that are particularly sensitive to energy deprivation. Here, MT-ND4 is linked to Leber hereditary optic neuropathy.