Diagnosing optic neuritis in the changing landscape of diagnostic criteria

Optic neuritis (ON) has over 60 distinct causes, only one of which is multiple sclerosis (MS). This poses a challenge for its prompt and accurate diagnosis. Patients frequently present with pain that worsens on eye movements, followed by reduced colour vision and acuity, progressing over a couple of weeks. The recovery phase typically follows a similar pattern, with pain improving before visual function. The interpretation of relevant investigations depends on their timing. This paper presents a practical approach to investigating, diagnosing and classifying ON in individuals with MS and other common neuroinflammatory conditions. We have taken into account the most recent consensus panel diagnostic criteria for ON (2022), neuromyelitis optica spectrum disease (NMOSD), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD, 2023) and MS (2024 revisions of the McDonald criteria). We use case histories to illustrate how best to use MRI and optical coherence tomography (OCT) in ON and discuss common clinical pitfalls.