Abstract
Optic neuritis (ON) is an inflammation of or around the optic nerve, frequently caused by infectious or immune-mediated inflammatory disorders. In the UK, its strongest association is with Multiple Sclerosis (MS), though the combined prevalence of other associated infectious and immune-mediated inflammatory diseases (I-IMID) is similar to that of MS-ON. Prompt identification and understanding of ON's underlying cause informs tailored management and prognosis. Several IMIDs linked to ON, such as aquaporin-4 antibody-associated optic neuritis (AQP4-ON), myelin oligodendrocyte glycoprotein antibody-associated optic neuritis (MOG-ON), and neuro-sarcoidosis, show remarkable response to corticosteroid treatment. Therefore, urgent investigation and treatment are crucial in cases 'atypical' for MS-ON. Following the 1992 Optic Neuritis Treatment Trial, clinical practice has evolved, with short-course high-dose corticosteroids considered safe and effective for most people. Timely recognition of patients who could benefit is critical to avoid irreversible vision loss. This review provides a practical guide and a summary of evidence on the investigation and management of acute optic neuritis. It reflects the knowledge and limitations of current evidence, framed through the neuro-ophthalmic perspective of clinical practice at multiple UK academic centres.