AKT · Ophthalmology/Neuro-ophthalmology

Optic neuritis

Inflammatory demyelination of the optic nerve (often MS-associated)

Overview

Inflammatory demyelination of the optic nerve, most often the first or a relapsing manifestation of multiple sclerosis. Subacute monocular visual loss over hours-days with pain on eye movement, dyschromatopsia (red desaturation) and a relative afferent pupillary defect. Treated with IV methylprednisolone (speeds recovery); MRI assesses MS risk.

Recognise

Subacute MONOCULAR visual loss over hours–days with PAIN ON EYE MOVEMENT
Reduced colour vision (red desaturation), central scotoma, and a relative afferent pupillary defect (RAPD)
Disc usually NORMAL (retrobulbar) or swollen (papillitis); vision typically recovers over weeks; often a young woman, MS-associated

Red flags

Bilateral, painless, very poor recovery, or no light perception → atypical: consider NMO/MOG, ischaemic or compressive causes
Suspected GCA (older, systemic features) → that is arteritic AION, not demyelinating optic neuritis

Differentials & how to tell them apart

Anterior ischaemic optic neuropathyolder, painless, altitudinal field loss, swollen pale disc; arteritic form = GCA

PapilloedemaBILATERAL disc swelling from raised ICP, vision often preserved early, no early RAPD

Compressive optic neuropathyslowly progressive painless loss, optic atrophy; imaging shows a mass

Leber hereditary optic neuropathyyoung man, painless sequential bilateral loss, maternal inheritance

Investigations

Clinical (RAPD, colour vision, fields); MRI brain + orbits with contrast (white-matter lesions → MS risk; enhancing optic nerve); consider NMO (aquaporin-4) / MOG antibodies in atypical cases.

Management

Refer; IV methylprednisolone for severe/disabling loss + MRI for MS risk

1Refer to ophthalmology/neurology. MRI brain + orbits to assess MS risk. Offer IV methylprednisolone to speed recovery in significant visual loss (it does not change the final outcome).Gate: Do NOT use low-dose ORAL prednisolone alone — it raises the recurrence rate; in atypical features check NMO/MOG antibodies and reconsider ischaemic/compressive causes
2Manage MS risk with neurology (DMTs if criteria met); monitor visual recovery (usually substantial over weeks).

IV methylprednisolone (then oral taper) — speeds recovery; does not change final acuity. Avoid low-dose ORAL steroid alone (higher recurrence)

Disease-modifying therapy for MS — if MS criteria met, under neurology

Key points

Painful monocular loss on eye movement + RAPD + red desaturation in a young woman = optic neuritis (think MS). 'The patient sees nothing and the doctor sees nothing' in retrobulbar cases — the disc looks normal.

Monitor & prognosis

Visual recovery; MS surveillance.

Good visual recovery in typical cases; relapses possible.

Source: RCOphth; NICE NG220 (MS); ONTT