This blog has been authored by Dr. Salma Yassine, Consultant Ophthalmologist in Paediatric & Neuro-ophthalmology

What is optic neuritis?

Optic neuritis occurs when our immune system mistakenly targets the substance covering your optic nerve, resulting in inflammation and damage to the myelin. This disrupts electrical impulses that travel from the eye to the brain, causing blurred or dark vision.

How does optic neuritis affect me?

Optic neuritis usually affects one eye. Symptoms might include:

• Pain: Eye pain that’s usually worsened by eye movement. Sometimes it presents as a dull ache behind the eye.
• Vision loss in one eye: Noticeable vision loss usually develops over hours or days and improves over several weeks to months. However, vision loss can be permanent in some people.
• Visual field loss: Central or peripheral vision loss
• Loss of colour: Colours appear less vivid

What causes optic neuritis?

The following autoimmune conditions often are associated with optic neuritis:

• Multiple sclerosis: It is a disease in which the autoimmune system attacks the myelin sheath covering nerve fibres in your brain. The risk of developing multiple sclerosis after optic neuritis increases further if an MRI scan shows demyelinating brain lesions

• Neuromyelitis Optica: In this condition, the inflammation affects the optic nerve and spinal cord. As a result, it often results in diminished visual recovery after an attack compared with MS.

• Myelin oligodendrocyte glycoprotein (MOG) antibody disorder: Like neuromyelitis optica, recurrent attacks of inflammation can occur in the optic nerve, spinal cord or brain. However, recovery from MOG attacks is usually better than recovery from neuromyelitis optica.

When symptoms of optic neuritis are more complex, other associated causes need to be considered, including infections, rheumatological diseases, and drugs or toxins (ethambutol or methanol)

Why do I need to see a neuro-ophthalmologist?

• Neuro-ophthalmologist is experienced in sorting out the differences between optic neuritis and other optic nerve diseases.
• During your office visit, the doctor will check your visual fields and scan your optic nerves
• Your doctor will order an MRI of the brain with special views of the orbits with contrast to confirm optic neuritis
• Your doctor may order other tests, such as blood tests or a chest X-ray

What are the possible complications?

• Optic nerve damage:  Most have permanent optic nerve damage after an episode of optic neuritis, but the damage might not cause permanent symptoms.
• Decreased visual acuity: Most people regain normal or near-normal vision within months, but a partial loss of colour discrimination might persist.

Side effects of treatment: Steroid medications used to treat optic neuritis suppress the immune system, which causes your body to become more susceptible to infections. It can also cause mood changes and weight gain.