OMG and neuromyelitis optica: Atypical ON can have a wide range of etiologies, like neuromyelitis optica (NMO) and neuromyelitis optica spectrum disorder (NMOSD), autoimmune optic neuropathy, optic neuropathies from systemic disease, chronic relapsing inflammatory optic neuropathy, myelin oligodendrocyte glycoprotein (MOG) and idiopathic neuroretinitis [6].