Optic neuritis - emergency/acute medicine guide
Definition and typical presentation
Optic neuritis is an acute inflammatory injury of the optic nerve that usually causes subacute, unilateral visual loss.
In adults it is most often demyelinating and associated with multiple sclerosis (MS), but it may also arise from NMOSD/MOG‑antibody disease, infection, sarcoid, compressive lesions, toxic/nutritional causes or ischaemic optic neuropathy.
NICE specifically highlights "loss or reduction of vision in one eye with painful eye movements" as a red‑flag presentation that warrants specialist assessment (NICE NG220).
Key clinical features
- Subacute monocular visual loss (hours-days), often central blurring or a central scotoma.
- Peri‑orbital/retro‑ocular pain, classically worse on eye movement.
- Colour desaturation (colours appear washed‑out).
- Relative afferent pupillary defect (RAPD) on swinging‑flashlight test - a sensitive sign of optic nerve dysfunction.
- Fundoscopy may be normal (retrobulbar neuritis) or show optic disc swelling (papillitis); a normal disc does not exclude optic neuritis.
Initial ED assessment
Focused history
- Onset and time course (exact time of first symptom).
- Progression and laterality.
- Previous similar episodes.