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Eyes & Vision

Optic Neuritis

Optic neuritis is inflammation of the optic nerve causing subacute visual loss, impaired colour vision, a relative afferent pupillary defect and often pain on eye movement; it needs urgent eye assessment and may be the first presentation of multiple sclerosis or antibody-mediated disease.

In a nutshell

Optic neuritis causes subacute visual loss, pain on eye movement, impaired colour vision and an RAPD, usually in one eye. The disc may be normal because the lesion is retrobulbar. It needs urgent ophthalmology and consultant-neurology assessment; MRI informs MS risk but does not diagnose MS alone. Specialist high-dose corticosteroids may speed recovery without improving final vision. Bilateral, severe, recurrent or poorly recovering disease raises concern for NMOSD or MOG-antibody disease.

Classic presentation

A young adult develops painful loss of vision in one eye over several days, with washed-out colours, a central field defect and an RAPD; the optic disc may look normal.

Key points

  • Subacute unilateral visual loss with pain on eye movement and red desaturation is the classic pattern.
  • The RAPD is elicited with the swinging light test and localises an asymmetric optic-nerve or retinal afferent lesion.
  • A normal optic disc does not exclude optic neuritis; retrobulbar disease is common.
  • Confirm with urgent ophthalmic assessment and refer confirmed isolated optic neuritis to consultant neurology.
  • MRI helps assess optic-nerve inflammation and MS risk, but MRI findings alone do not establish MS.
  • Steroids may speed recovery but do not usually change final vision; avoid standard-dose oral prednisolone alone.
  • Bilateral, severe, recurrent, painless or poorly recovering disease needs an NMOSD/MOG and alternative-cause work-up.

First-line investigation

Visual acuity, colour vision, pupils/RAPD, fields, motility and fundus assessment urgently, followed by specialist-directed MRI of the brain and orbits.

Management

Assess urgently and exclude dangerous mimics

  • Document acuity, colour vision, RAPD, fields and fundus; suspected optic neuritis with visual loss needs urgent ophthalmic assessment. In older patients or with GCA symptoms, use the emergency GCA pathway.2,9

Confirm the optic-nerve lesion and phenotype

  • Arrange specialist MRI of brain/orbits and targeted blood tests when atypical; use the clinical picture, MRI and laboratory findings together rather than diagnosing MS from MRI alone.1,4,7

Refer confirmed isolated optic neuritis to neurology

  • NICE recommends consultant-neurology assessment after isolated optic neuritis has been confirmed by an ophthalmologist; classify clinically isolated syndrome, MS, NMOSD, MOG-antibody disease or another cause.1

Use specialist high-dose steroid or neuroimmunology pathways

  • High-dose methylprednisolone may speed recovery in severe or significant attacks; severe NMOSD/MOG attacks may need plasma exchange or immunoglobulin. Keep doses and long-term immunotherapy within specialist and BNF/local protocols.5,4,6

Monitor recovery and future neurological disease

  • Follow acuity, colour, fields and OCT as appropriate; if MS criteria are not met, arrange planned review and give clear advice about new neurological symptoms. Explain Uhthoff phenomenon and check current DVLA visual requirements where driving is relevant.1,3

Exam traps

  • A normal-looking disc does not rule out optic neuritis.
  • The RAPD is a swinging-light finding, not unequal pupil size.
  • MRI lesions support diagnostic assessment and risk stratification but do not diagnose MS in isolation.
  • Bilateral, painless, very severe, recurrent or progressive disease is atypical and should prompt NMOSD/MOG or structural/infectious investigation.
  • Steroids speed visual recovery but do not usually improve the final visual outcome; standard-dose oral prednisolone alone is inappropriate.
  • Transient heat- or exercise-related blurring is Uhthoff phenomenon and is not automatically a new relapse.

Illustrations

Right optic neuritis on orbital MRIMultipanel orbital MRI showing asymmetric increased signal and enhancement of the right optic nerve in optic neuritis.ICON2022, Wikimedia Commons · CC-BY-SA-4.0
Axial FLAIR brain MRI: periventricular white-matter lesionAn axial FLAIR brain MRI showing periventricular ovoid white-matter lesions, illustrating a finding that can contribute to MS diagnostic assessment but cannot establish MS in isolation.James Heilman, MD, Wikimedia Commons · CC-BY-SA-4.0

Key sources

  1. NICE, Multiple sclerosis in adults: management (NG220 recommendations, last updated 3 June 2026)Updated 3 Jun 2026
  2. NHS Cornwall and Isles of Scilly, Optic nerve referral guidance (RMS clinical referral guideline, reviewed 30 September 2025)Updated 30 Sept 2025
  3. Hull University Teaching Hospitals NHS Trust, Optic neuritis (Patient information HEY1422/2023, updated 30 November 2023)Updated 30 Nov 2023
  4. NHS, Neuromyelitis optica (NHS Health A to Z, last reviewed 20 December 2024)Updated 20 Dec 2024
  5. NHS Highland, Optic neuritis guideline (Adult therapeutic ophthalmology emergency pathway)
  6. BNF, Methylprednisolone (BNF drug monograph)
  7. North West London Pathology, MOG antibody (NHS laboratory test information)
  8. University Hospitals Birmingham, Multiple sclerosis diagnosis and symptoms (NHS referral pathway, reviewed 4 December 2024)Updated 4 Dec 2024
  9. NICE CKS, Giant cell arteritis (Clinical Knowledge Summary)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.