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Optic Neuritis

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Optic neuritis (ON)\: in
with multiple sclerosis (MS).
Typical ON\: often linked to MS; may occur as a clinically isolated syndrome initially.
Atypical ON causes\: antibody-mediated (NMOSD, MOGAD), non-infectious (neurosarcoidosis, autoimmune diseases),
infectious (syphilis, Lyme disease), post-infectious.
Pathophysiology\: autoimmune mechanism; T-cells destroy myelin sheath; in
genetics, and environment (low vitamin D, UV exposure, smoking, obesity).
Risk factors\: MS diagnosis, female sex (3\:1 ratio), young age (20-50 years), higher latitude populations.
Symptoms\: acute/subacute unilateral visual loss, retrobulbar/peri-ocular pain (worse with eye movements), photopsias,
visual
Examination\: visual acuity, colour vision, RAPD, fundoscopy (optic nerve swelling or pallor), extraocular movements
(internuclear ophthalmoplegia in MS).
Di
compressive/in
Investigations\: MRI with gadolinium contrast (optic nerve enhancement, MS lesions), lumbar puncture for CSF analysis (if
MRI normal), additional tests for atypical features.
Management\: high-dose corticosteroids (IV methylprednisolone 1g daily for 3 days, followed by oral prednisolone taper),
avoid oral prednisolone alone; consider interferon-beta and glatiramer acetate for MS prevention.
Complications\: >90% recover vision to 6/12 or better within a year; persistent issues may include contrast sensitivity, RAPD,
colour perception; recurrence risk ~30% at 5 years; 15-year MS risk ~50% (25% with normal MRI, 72% with lesions).
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Introduction

Optic neuritis (ON) is an in
acute or subacute visual loss. It frequently occurs in association with multiple sclerosis (MS).

Aetiology

Typical (demyelinating) ON is strongly associated with MS. It may initially occur as a clinically isolated syndrome without
evidence of generalised demyelination, however, this eventually develops in a signi
Other less common (atypical) causes of ON include\:
1
Antibody-mediated\: neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein
antibody disease (MOGAD)
Non-infectious\: neurosarcoidosis and systemic autoimmune conditions such as systemic lupus erythematosus
Infectious\: syphilis, Lyme disease, cat-scratch disease, herpes zoster, sinus disease
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Post-infectious\: following an acute infection or immunisation

Pathophysiology

As in MS, the primary mechanism is autoimmune. T-cells are directed against the central nervous system myelin antigens
which destroy the myelin sheath.
Other signi
and the environment (low vitamin D, low UV exposure, smoking and obesity).
2

Risk factors

Risk factors for ON include\:
2,3,4
Known diagnosis of MS\: up to 70% of patients with MS will have at least one episode. Optic neuritis can be the presenting
feature of MS in up to 20% of cases.
Female sex\: there is a female predominance by a ratio of 3\:1
Young age\: most patients are aged 20-50 years
Higher latitude\: the incidence is higher for populations at higher or lower latitudes (the northern United States, northern
and western Europe, southern Australia and New Zealand) compared with areas closer to the equator

Clinical features

History

Typical symptoms of demyelinating ON include\:
5,6,7
Acute to subacute unilateral loss of vision\: the visual acuity upon testing can vary from being normal (6/6) to rarely
becoming ‘no perception of light’
, i.e. inability to tell when a bright
Retrobulbar and peri-ocular pain\: this is present in >90% of cases and is exacerbated by eye movements and may
precede or occur with visual loss. The pain is believed to occur due to close proximity of rectus muscle insertions to the
in
Photopsias (
Visual
Reduced contrast sensitivity and colour vision.
The vision worsens over hours to days, but recovery starts within two weeks with or without treatment. The visual acuity
may recover to near normal but permanent abnormalities of colour perception, contrast sensitivity and visual
occur.

Clinical examination

All patients with suspected optic neuritis should undergo a comprehensive ophthalmic, cranial nerve and neurological
examination.
The ophthalmic examination should include\:
4
Visual acuity testing with a Snellen chart
Colour vision assessment with an Ishihara test
Testing for a relative a\: this will be positive for the a
existing disease in the contralateral eye.
Fundoscopy\: swelling of the optic nerve may be visible in a third of patients and is typically mild. However, most patients
have retrobulbar involvement therefore the optic nerve appears normal. Over time, the optic nerve will develop pallor.
Testing extraocular muscle movements\: expected to be normal in ON but may detect internuclear ophthalmoplegia
(common in multiple sclerosis)
For more information on clinical examination multiple sclerosis.
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Alternative diagnoses should be considered in patients with atypical features.
6
Di
1
Atypical causes of ON (see aetiology section)
Ischaemic\: giant cell arteritis must be considered in a patient over the age of 50
Hereditary\: Leber’s hereditary optic neuropathy
Compressive/in
Nutritional/toxic\: B12/folate de
Trauma/radiation

Investigations

Optic neuritis is a clinical diagnosis in patients with typical features of demyelinating ON.
An MRI of the brain and orbits with gadolinium contrast will show enhancement of the optic nerve, con
diagnosis. MRI may also identify any white matter lesions suggestive of MS (Figure 1).
Figure 1. Optic neuritis of the left optic
nerve demonstrating high T2 signal on
MRI
A lumbar puncture for CSF analysis may be useful to support the diagnosis of MS if the MRI is normal.
Patients with atypical features may require additional laboratory and radiological investigations depending on the clinical
context to exclude other causes of optic neuropathy.

Management

Optic neuritis treatment trial (ONTT)6
The Optic Neuritis Treatment Trial (ONTT) was a landmark study which demonstrated an increased rate of visual recovery in
typical ON patients treated with high-dose systemic (intravenous) steroids.
However, the
ine
the risk of developing MS in patients with typical ON for the

Medical management

Patients with typical ON should be started on high-dose corticosteroid therapy.
The typical regimen is intravenous methylprednisolone 1g daily for three days followed by an oral prednisolone taper
(1mg/kg for 11 days).
Oral methylprednisolone 500mg once a day for
but its use remains controversial.
The decision to treat may depend on several factors. Treatment is more likely to be o
profound visual loss in a solitary eye, or in cases of severe pain. 3
It is important to consider the signi
which can be associated with high-dose steroids, and counsel the patient appropriately.
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Trials have shown that both interferon-beta and glatiramer acetate prolong the time to development of clinically de
MS in patients with ON and at least two white matter lesions on MRI.
3,8

Complications

Patients with ON have favourable outcomes with >90% recovering vision to 6/12 or better within one year and this was
sustained at 15 years of follow-up in the ONTT.
9
However other abnormalities such as contrast sensitivity, relative a
perception may persist.
The risk of recurrence in the a
10
An episode of ON does not imply a de
developing MS is 50%. The risk is 25% for patients with a normal MRI and up to 72% for those with one or more lesions on
MRI.
11

References

Kanski JJ, Bowling B. Clinical Ophthalmology\: A Systematic Approach. Edinburgh, Elsevier/Saunders; 2015.
Baecher-Allan C, Kaskow BJ, Weiner HL. Multiple Sclerosis\: Mechanisms and Immunotherapy. Neuron. 2018;97(4)\:742–68.
Pau D, al Zubidi N, Yalamanchili S, Plant GT, Lee AG. Optic neuritis. Eye. 2011;25(7)\:833–42.
Denniston A, Murray P. Oxford Handbook of Ophthalmology. 4th ed. OUP Oxford; 2018.
Keltner JL, Johnson CA, Cello KE, Dontchev M, Gal RL, Beck RW. Visual
from the optic neuritis treatment trial from baseline through 15 years. Archives of Ophthalmology 2010;128(3)\:330–7.
Beck RW, Cleary PA, Anderson MM, et al. A Randomized, Controlled Trial of Corticosteroids in the Treatment of Acute Optic
Neuritis. New England Journal of Medicine [Internet] 1992;326(9)\:581–8. Available from\: [LINK]
The Optic Neuritis Study Group. The Clinical Pro
Archives of Ophthalmology [Internet] 1991;109(12)\:1673–8. Available from\: [LINK]
Comi G, Martinelli V, Rodegher M, et al. E
patients with clinically isolated syndrome (PreCISe study)\: a randomised, double-blind, placebo-controlled trial. The Lancet
[Internet] 2009;374(9700)\:1503–11. Available from\: [LINK]
The Optic Neuritis Study Group. Visual Function 15 Years after Optic Neuritis\: A Final Follow-up Report from the Optic
Neuritis Treatment Trial. Ophthalmology [Internet] 2008;115(6)\:1079-1082.e5. Available from\: [LINK]
The Optic Neuritis Study Group. Visual Function 5 Years After Optic Neuritis\: Experience of the Optic Neuritis Treatment Trial.
Archives of Ophthalmology [Internet] 1997;115(12)\:1545–52. Available from\: [LINK]
The Optic Neuritis Study Group. Multiple Sclerosis Risk After Optic Neuritis\: Final Optic Neuritis Treatment Trial Follow-up.
Archives of Neurology [Internet] 2008;65(6)\:727–32. Available from\: [LINK]

Image references

Figure 1. Dr Mohammad A. ElBeialy / Radiopaedia.org. From the case rID\: 38584. License\: [CC BY-NC-SA]

Related notes

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Age-related Macular Degeneration (ARMD)
Amblyopia
Ametropia
Anisocoria
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Contents

Introduction
Aetiology
Risk factors
Clinical features
Di
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