Optic Neuritis

Article Last Updated:29/05/2026

Optic Neuritis

Optic neuritis refers to the inflammation of the optic nerve (cranial nerve II), classically associated with multiple sclerosis.

This updated UKMLA guide to optic neuritis covers causes, risk factors, symptoms, diagnosis, and management.

Causes and Risk Factors

Optic neuritis is most commonly caused by inflammatory demyelination of the optic nerve

Multiple sclerosis – classic and most common association
- Optic neuritis is often the first sign of multiple sclerosis (see the Multiple Sclerosis (MS) article for more information)
- ~50% of multiple sclerosis patients experience at least 1 episode of optic neuritis over a 15-year period
Neuromyelitis optica spectrum disorder
Systemic autoimmune diseases (e.g. sarcoidosis, SLE)

Other causes:

Infection
- Viral: HSV, VZV, EBV, measles, CMV
- Bacterial: syphilis, Lyme disease, tuberculosis
Medications
- Ethambutol
- Amiodarone
- Linezolid
Vitamin B12 deficiency

Risk factors (broadly overlap with those for multiple sclerosis):

Young adults 20-50 y/o
Females
Caucasians
HLA-B27 and HLA DRB1

Clinical Features

Typically presents with an acute / subacute onset of unilateral symptoms.

CRAP is a useful mnemonic:

Letter	Corresponding category	Description
C	Central scotoma	Central scotoma (blind spots in the centre of vision) – most common type of visual field defect
R	RAPD (Marcus Gunn pupil)	Elicited by the swinging torch test: Normal: Both pupils remain constricted as the light moves from one eye to the other. In RAPD: When the light is moved from the normal eye to the affected eye, both pupils dilate. Note that RAPD is not diagnostic of one specific disease, it simply indicates reduced afferent input from one eye, usually due to retinal or optic nerve pathology
R	Red desaturation	Difficulty perceiving colours Red desaturation Colour appears “washed out”
A	Acuity (visual)	Acute / subacute vision loss Decline in visual acuity
P	Pain	Eye pain (often develops a few days before vision loss) Worsens with eye movement

Fundoscopic appearance depends on the type of optic neuritis:

The optic disc appears normal in most cases (retrobulbar optic neuritis)
1/3 cases will exhibit optic disc swelling and hyperaemia (papillitis)

Disease course and progression:

After the acute onset, optic neuritis typically stabilises in a subacute stage. Vision often recovers spontaneously within a few weeks (near 90% of patients achieve near-normal vision by 6 months, irrespective of treatment)
Optic neuritis can recur, entering a chronic or recurrent stage – esp. when associated with MS or NMOSD

Investigation and Diagnosis

The diagnosis of optic neuritis itself is primarily a clinical diagnosis (see above)

If optic neuritis is suspected, further investigations are necessary to check for any underlying causes:

Gold standard imaging: MRI brain and orbits with gadolinium contrast
- Used to assess the risk of diagnosing multiple sclerosis
- If the diagnosis of optic neuritis is clinically uncertain, enhancement of the optic nerve can confirm the diagnosis
CSF analysis (via lumbar puncture) – presence of oligoclonal bands in the CSF, but not in the serum, is pathognomonic for MS
Serology
- Antiaquaporin-4 IgG antibodies to exclude NMOSD
- Myelin oligodendrocyte glycoprotein IgG antibodies to exclude MOGAD
- Autoimmune panel including ANA, if SLE is suspected
Infection work-up (if an infectious trigger is suspected – syphilis, Lyme disease, tuberculosis testing)

Management

If optic neuritis is suspected → refer to both ophthalmology and neurology.

Acute management of optic neuritis:

1st line: high-dose IV methylprednisolone, followed by an oral prednisolone taper
- Oral corticosteroids alone should be avoided, as this increases the risk of recurrent attacks
If severe optic neuritis does NOT respond to IV steroids → plasma exchange

Technically, corticosteroids are mainly used for inflammatory / autoimmune optic neuritis, especially those associated with multiple sclerosis, NMOSD, and systemic inflammatory causes (e.g. SLE).

Infective causes must be excluded or treated appropriately, as giving steroids alone in infection may worsen the underlying infection.

Long-term management involves identifying and managing any underlying causes:

Multiple sclerosis → disease-modifying therapies (see the Multiple Sclerosis (MS) article for more information)
NMOSD and autoimmune causes → immunosuppressants and monoclonal antibodies
SLE → see the Systemic Lupus Erythematosus (SLE) article
Sarcoidosis → see the Sarcoidosis article