Optic neuritis (ON)
ON is the most common clinical presentation of MOGAD in adults, comprising around 50% of MOGAD phenotypes at onset, as shown by three large national studies from the UK, France, and Sri Lanka (6,25,36). Clinical symptoms of ON include blurred vision and reduced visual acuity or visual loss, as well as eye pain especially retrobulbar pain with eye movement (37). ON in MOGAD is often bilateral, either concurrently or sequentially (38,39). Therefore, bilateral ON represents an important clinical presentation that can help differentiate MOGAD-ON from ON in multiple sclerosis (MS-ON). However, incidence of bilateral ON in paediatric patients is similarly common in AQP4-IgG positive NMOSD as it is in MOGAD patients. Differences include a more anterior affection of the optic nerve in MOGAD with optic nerve head swelling and retrobulbar involvement (40).