Optic Neuritis

Optic neuritis is a potentially blinding inflammatory condition of the optic nerve.

The inflammation occurs when the immune system of one's body attacks the optic nerve or its covering (myelin sheath). Optic neuritis is a broad term describing a condition which can be caused by a wide range of underlying diseases.

​ Swollen right optic disc in a patient with bilateral optic neuritis	​ Swollen left optic disc in a patient with bilateral optic neuritis
​ Right Visual field defect in the same patient at the time of presentation	​ Left visual field defect in the same patient at the time of presentation
Resolution of right optic disc swelling in the same patient two weeks later	Resolution of left optic disc swelling in the same patient two weeks later

What causes optic neuritis?

The commonest cause of optic nerve inflammation in Singapore is demyelinating (destruction of the myelin sheath of the optic nerve), the underlying cause of which is unknown, although a viral infection may be implicated.

In countries with a predominantly Caucasian population, this demyelination may be a manifestation of a neurological condition known as multiple sclerosis (MS).

Other causes may be due to and not limited to:

• Association with systemic autoimmune/inflammatory diseases such as systemic lupus erythematous (SLE), Sjogren's Syndrome, sarcoidosis and Granulomatosis with Polyangiitis (GPA) also known as “Wegener's Granulomatosis”
• Isolated autoimmune optic neuritis, which is not associated with any defined systemic autoimmune/inflammatory disease like those mentioned above
• Neuromyelitis optic  (NMO) or Devic's disease
• Anti-MOG (Myelin-oligodendrocyte-glycoprotein) related optic neuritis
• Chronic relapsing inflammatory optic neuropathy (CRION)

Patients with optic neuritis may experience sudden unilateral or bilateral visual loss that progressively worsens. Pain with eye movements may be present.

Vision is variably affected and colour vision is typically poor. There may or may not be swelling of the optic nerve head.

Patients with a demyelinating cause of optic neuritis usually have a good visual recovery but intravenous steroid followed by oral steroids may be used to speed up visual recovery.

In contrast, for the other causes of optic neuritis, the final visual outcome may be poor if optic neuritis is left untreated. Clinical examination complemented by relevant investigations such as visual field testing, blood tests and MRI are important to differentiate the different types of optic neuritis and their appropriate treatment.