​What is the optic nerve for?


The role of the optic nerve is to carry visual information from the eye to the brain.

Optic neuritis: What you need to know

Optic neuritis is inflammation of the optic nerve and / or its covering (myelin sheath).

"Inflammation occurs when the immune system in the body mistakenly attacks the optic nerve and / or its myelin sheath. Optic neuritis is a broad term describing a condition which may be caused by a wide range of underlying diseases," explains the Neuro-Ophthalmology Department from Singapore National Eye Centre (SNEC), a member of the SingHealth group.

Possible causes of optic neuritis

  • Idiopathic or unknown, although a viral infection may be responsible

  • Multiple sclerosis (MS)

  • Neuromyelitis optica (NMO)

  • Myelin oligodendrocyte glycoprotein (MOG)-associated optic neuritis

  • Autoimmune conditions
    Systemic lupus erythematosus (SLE), Sjogren’s syndrome, sarcoidosis, granulomatosus with polyangiitis etc
    (To learn more about autoimmune conditions / rheumatological diseases, read this article here)

  • Infections
    Bacterial infections such as Lyme disease, syphilis etc, viral infections such as measles, mumps and herpes

Examination by your ophthalmologist, together with investigations such as blood tests and MRI are important to help differentiate the different types of optic neuritis.

Symptoms of optic neuritis

Symptoms may affect one or both eyes, and include:

  • Blurring of vision
    You may notice sudden vision loss developing over days

  • Loss of colour vision
    You may notice that colours appear less vibrant than usual.

  • Eye pain
    This may feel like a dull ache behind the eye. Your eye pain may be worsened by eye movement.

Diagnosis of optic neuritis

You will need to see an ophthalmologist to make the diagnosis. Your ophthalmologist will take a medical history and perform a full eye examination.

Your optic disc (part of the optic nerve that is visible in the eye) may or may not appear swollen.                                               

Shown above left: Swollen left optic disc in a patient with optic neuritis
Shown above right: Resolution of left optic disc swelling in the same patient two weeks later

The following tests may be required in order to diagnose and help distinguish the different causes of optic neuritis:

  • Visual field test
    Measures the degree and pattern of visual loss in your field of vision

  • Optical coherence tomography (OCT)
    Measures the thickness of your eye’s retinal nerve fibre layer, which may be thicker in the acute stage of optic neuritis in the presence of optic disc swelling, or thinner in the late stage due to optic nerve damage

  • Blood tests
    To check for infections or specific antibodies that may cause the different types of optic neuritis

  • Magnetic resonance imaging (MRI)
    Scan to look for changes in your optic nerve or brain. You may also receive an injection of a contrast (dye) during the scan.

  • Lumbar puncture
    May be performed to analyse the fluid surrounding your brain and spine (cerebrospinal fluid) for abnormalities.

Treatment for optic neuritis

Some patients with optic neuritis, especially the idiopathic type, may get better without any treatment. However, many patients need treatment to improve their vision. The aim of treatment is to reduce inflammation and limit the amount of optic nerve damage.

1. Intravenous Methylprednisolone

A three to five-day course of high dose intravenous corticosteroids may be offered to reduce inflammation in the optic nerve. This is usually followed by a longer course of oral corticosteroids.

Possible side effects from steroid treatment include:

  • Hypertension, irregular heart beat

  • High blood sugar

  • Electrolyte (salt) imbalance in the blood

  • Gastric bleeding (usually in patients with pre-existing gastric ulcers)

  • Infections

  • Weight gain

  • Osteoporosis

  • Mood changes, insomnia

Let your doctor know if you have a history of:

2. Plasma Exchange Therapy

When steroid therapy fails and severe vision loss persists, this treatment may be offered to help you recover some vision.

Plasma is the liquid portion of your blood that contains disease-causing antibodies. This treatment removes plasma from your blood and replaces it with a substitute.

Commonly asked questions about treatment for optic neuritis

1. Will my vision improve completely after treatment?

Most patients recover their vision completely. It may take up to one year. This tends to be the case when optic neuritis is not related to an underlying health condition (see above, “Possible causes of optic neuritis"). In some cases, however, vision recovery may be incomplete.

2. Will my episode of optic neuritis occur again?

If you have an underlying health condition (see above, "Possible causes of optic neuritis”) that triggered the optic neuritis, this has to be treated. Otherwise, optic neuritis may recur.

Ref: H24

To learn about other visual problems caused by the brain and nervous system, visit here.

To learn about 10 common eye conditions affecting eye health, visit here.