Optic neuritis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Optic neuritis is an inflammatory condition affecting the optic nerve, often associated with demyelinating diseases such as multiple sclerosis, leading to vision loss and eye pain.

Aetiology

• Demyelinating disease: multiple sclerosis (most common association).
• Infectious causes: viral infections (e.g., herpes zoster, syphilis, tuberculosis).
• Autoimmune disorders: neuromyelitis optica, sarcoidosis, systemic lupus erythematosus.
• Drug-induced: ethambutol, isoniazid, amiodarone.

Pathophysiology

• Immune-mediated inflammation leads to demyelination of the optic nerve.
• Axonal injury results in visual impairment and pain due to inflammation.
• Remyelination may occur, but repeated episodes increase the risk of permanent damage.

Risk Factors

• Female sex (higher prevalence in multiple sclerosis).
• Young adults (typically 20-40 years old).
• Personal or family history of autoimmune diseases.
• Prior viral infections.

Signs and Symptoms

• Monocular vision loss: usually sudden and progressive over days.
• Eye pain: worsened by eye movement.
• Dyschromatopsia: impaired colour vision, particularly red desaturation.
• Relative afferent pupillary defect (RAPD): reduced direct pupillary response in the affected eye.
• Phosphenes: flashes of light with eye movement.

Investigations

• Clinical assessment: fundoscopy may show optic disc swelling in papillitis; normal in retrobulbar neuritis.
• MRI brain and orbits: detects white matter lesions suggestive of multiple sclerosis.
• Blood tests: inflammatory markers, infectious serology if suspected.

Management

These are specialist treatments mainly

1. Acute Treatment:

• High-dose IV corticosteroids: methylprednisolone for severe cases.
• Oral corticosteroids: used in some cases but may increase recurrence risk.

2. Disease Modification:

• Immunomodulatory therapy if associated with multiple sclerosis.

3. Supportive Care:

• Visual rehabilitation for persistent deficits.
• Regular ophthalmic and neurological follow up.

4. Referral:

• Neurology: if multiple sclerosis or neuromyelitis optica is suspected.
• Ophthalmology: for acute visual symptoms and monitoring.
• Infectious diseases: if an infectious cause is suspected.

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