About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Unilateral painful visual loss worsening over days — pain worse on eye movement
- Key: RAPD, reduced colour vision (red desaturation), central scotoma
- Most are retrobulbar ("patient sees nothing, doctor sees nothing")
- ~50% develop MS within 15 years; MRI brain is essential
- IV methylprednisolone speeds recovery but does NOT change final outcome (ONTT)
Overview
Optic neuritis is inflammatory demyelination of the optic nerve, most commonly idiopathic and associated with MS. Other causes include NMOSD, sarcoidosis, and infections. In retrobulbar neuritis (most cases), the disc appears normal. Vision typically worsens over 1–2 weeks then recovers over 4–12 weeks.
Epidemiology
Incidence ~3–5 per 100,000. Most common in women aged 20–40. ~50% develop MS within 15 years (ONTT: 72% if abnormal baseline MRI vs 25% if normal).
Clinical Features
Symptoms
Unilateral visual loss developing over hours to days
Pain on eye movement (>90%)
Reduced colour vision — especially red desaturation
Uhthoff phenomenon: vision worsens with heat/exercise
Bilateral or very severe loss — consider NMOSD
Signs
RAPD — essential clinical sign
Reduced VA and colour vision (Ishihara)
Optic disc normal (retrobulbar) or swollen (papillitis)
Temporal disc pallor on recovery
Investigations
First-line
VA, colour vision (Ishihara), visual fieldsReduced VA, red desaturation, central scotoma
Pupil examinationRAPD is the most important clinical sign
FundoscopyNormal disc (retrobulbar) or swollen (papillitis)
Second-line
MRI brain and orbits with gadoliniumESSENTIAL — optic nerve enhancement + white matter lesions indicate MS risk
BloodsFBC, CRP/ESR, ANA, anti-aquaporin-4 if NMOSD suspected
Specialist
Visual evoked potentials (VEPs)Delayed P100 latency confirms optic nerve conduction delay
OCT RNFLMeasures nerve fibre layer thinning — indicates axonal loss
Management
ONTT + NICE CG186 (Multiple sclerosis)1
Acute optic neuritis
- IV methylprednisolone 1 g/day for 3 days — speeds recovery, does NOT improve final outcome
- Oral prednisolone ALONE is NOT recommended (ONTT — increases recurrence)
- Most recover to ≥6/9 within 12 weeks without treatment
2
MS investigation
- MRI brain essential after first episode
- Neurology referral for all patients
3
Long-term
- Disease-modifying therapy if MS diagnosed
- If NMOSD (anti-aquaporin-4 positive): rituximab, azathioprine, mycophenolate
Complications
- Multiple sclerosis: ~50% within 15 years
- Persistent visual deficits: Subtle colour and contrast impairment
- Optic atrophy: Temporal pallor
- Recurrence: ~28% within 5 years
UKMLA Exam Tips
- 1Painful visual loss + pain on eye movement + RAPD + young woman = optic neuritis — think MS
- 2"Patient sees nothing, doctor sees nothing" = retrobulbar optic neuritis
- 3Red desaturation: reds appear washed out in the affected eye
- 4Uhthoff phenomenon: vision worsens with heat/exercise — classic exam question
- 5IV methylprednisolone speeds recovery but does NOT improve long-term outcome
- 6Oral prednisolone ALONE increases recurrence — never give alone (ONTT)
- 7MRI brain is essential — white matter lesions predict MS
practicetest your knowledge on optic neuritisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — ophthalmology and beyond.
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