Although oral prednisolone is the first-line treatment for preventing recurrent optic neuritis (ON) after the completion of acute-phase treatment, especially anti-aquaporin 4 (AQP4) antibody-positive ON, and anti-myelin oligodendrocyte glycoprotein (MOG) antibody-positive ON, some patients experience relapses. This evidence concerns the gene AQP4 and optic neuritis.