Background: Natural history of optic neuritis (OPN) has not been studied in India.
Aim: To study consecutive patients with optic neuritis as the initial manifestation of the neurologic disease and with disease duration of 3 or more years registered in the Mangalore Demyelinating Disease Registry.
Materials and methods: The study included 59 patients with a primary diagnosis of optic neuritis (confirmed by either an ophthalmologist or a neurologist or both). All the patients were investigated and followed-up in the clinic.
Results: During the follow-up of the 59 patients, 29 (49%) patients developed multiple sclerosis (MS); 3 (5%) patients neuromyelitis optica (NMO); and 13 (22%) patients chronic relapsing inflammatory optic neuritis (CRION), while the remaining 14 (24%) did not either progress or relapse, monophasic OPN. An initial abnormal magnetic resonance imaging predicted conversion to MS in all 7 patients who had imaging at onset. Patients with NMO were left with significant residual visual loss distinguishing NMO from MS. In this large series of patients with CRION, nearly 50% of patients had deterioration in vision while steroids were being tapered. Long-term immunosuppression was essential for maintaining good visual outcome in both NMO and CRION.
Conclusions: Optic neuritis in India appears similar to that in the West with nearly 50% developing MS in the long term.