Update on Optic Neuritis: An International View.

Previously, optic neuritis was thought to be typical, i.e. idiopathic or multiple sclerosis (MS) related, associated with a good visual prognosis, or atypical, i.e. not associated with MS and requiring corticosteroids or plasma exchange for vision to recover. More recently, the importance of optic neuritis in neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein (MOG) antibody disease has become more appreciated. The results of the Optic Neuritis Treatment Trial (ONTT) has influenced how optic neuritis is treated around the world. For this review we surveyed the international literature on optic neuritis in adults. Our aims were first to find the reported incidence of optic neuritis in different countries and to ascertain what percentage of cases were seropositive for anti-aquaporin 4 and anti-MOG antibodies, and second, to document the presenting features, treatment, and outcomes from a first episode of the different types of optic neuritis from these countries, and to compare the results with the outcomes of the ONTT cohort. From these data we have sought to highlight where ambiguities currently lie in how to manage optic neuritis and have made recommendations as to how future treatment trials in optic neuritis should be carried out in the current antibody testing era.