• Subacute vision loss over days, pain with eye movement (90%), dyschromatopsia, RAPD; disc normal (retrobulbar) in 2/3.
• MRI brain & orbits with gadolinium — white-matter lesions predict MS (ONTT).
• Atypical features (no pain, severe/bilateral, no recovery by 3 weeks, marked disc edema) → test AQP4 and MOG antibodies.

ONTT: IV methylprednisolone speeds recovery but does not change final acuity; oral prednisone alone increased recurrence and is not recommended.