Optic neuritis is inflammation of the optic nerve. It is the main cause of acute visual impairment in young adults and middle-aged adults. Vision loss is usually accompanied by eye pain.

Definition of optic neuritis

Optic neuritis is a type of optic neuropathy characterized by inflammation of the optic nerve. Also called nerve II, this cranial nerve transmits visual information from the eyes to the brain.

We often speak of retrobulbar optic neuritis (NORB) to specify that the inflammation of the optic nerve takes place behind the eyeball and is not accompanied by papillary edema (swelling of the optic disc). If optic neuritis is accompanied by papillary edema, we tend to speak of neuropapillitis, papillitis or anterior inflammatory optic neuropathy. 

Causes of optic neuritis

Retrobulbar optic neuritis is one of the most common manifestations of multiple sclerosis, an autoimmune disease affecting the central nervous system. While the immune system aims to protect the body, it attacks multiple sclerosis with the myelin surrounding and protecting nerve fibers. Multiple sclerosis is said to be a demyelinating disease.

Retrobulbar optic neuritis can be caused by demyelinating diseases other than multiple sclerosis. It can, for example, be the consequence of neuromyelitis optic which, unlike multiple sclerosis, only affects the myelin sheath in the eyes and the spinal cord.

Besides demyelinating diseases, optic neuritis can have other causes. It may be due to:

• infectious diseases, in particular during viral encephalitis, meningitis, sinusitis, tuberculosis, syphilis or even HIV infection (human immunodeficiency virus);
• metastases (secondary cancers) affecting the optic nerve;
• absorption of toxic substances affecting the optic nerve such as lead, methanol, arsenic, tobacco, quinine (a substance used as an antimalarial) and salicylates (substances found in certain plants and in several analgesics);
• a nutritional deficiency, and more exactly a deficiency in vitamins of group B.

Cases of optic neuritis have also been associated with diabetes, atherosclerosis, anemia, systemic autoimmune disease, Graves’ ophthalmopathy, bee stings and trauma.

Diagnosis of optic neuritis

When faced with eye pain and a sudden drop in visual ability, a healthcare professional may suspect optic neuritis. Neurological and neuroradiological examinations can confirm the diagnosis and examine possible causes.

People affected by optic neuritis

Optic neuritis most commonly occurs in adults between the ages of 20 and 40. It preferentially affects Caucasian populations and the female sex. Its annual incidence is estimated between 1 and 5 cases per 100.

Loss of vision

Inflammation of the optic nerve disrupts the transmission of visual information from the eyes to the brain, resulting in a sudden drop in visual capacity. This can last from a few hours to a few days. It can be partial but can also be total and cause blindness.

Eye pain

The loss of vision is usually accompanied by pain in the eyes. These are often moderate but can be more intense during eye movements.

The main treatment for optic neuritis is to treat its cause. Appropriate management allows remission of inflammation of the optic nerve. The pains disappear and the vision improves.

A medical follow-up is recommended. Sometimes visual recovery is imperfect and inflammation continues. In this case, an anti-inflammatory treatment with corticosteroids is usually prescribed.

To date, there is no specific prevention for optic neuritis. However, it is recommended to regularly consult an ophthalmologist to assess visual capacity, and thus identify any deterioration as soon as possible.