Retrobulbar optic neuritis – NORB

Optic neuritis is an inflammation of the optic nerve. This nerve carries images received and converted into electrical signals by the eye to the brain. In cases of inflammation, infection, or severance of the optic nerve, visual disturbances develop: decreased vision, scotoma, etc. Not all causes of optic neuritis are clearly understood. It is most often a manifestation of multiple sclerosis (MS), an autoimmune disease: your body attacks your optic nerve. The diagnosis is usually suspected by an ophthalmologist and confirmed by a radiologist performing an MRI. Treatment is managed by a neurologist. It relies on anti-inflammatory drugs (corticosteroid injections) and treatment of the underlying cause.

What is NORB?

Optic neuritis is a sudden inflammation of the optic nerve resulting in impaired transmission of images from the eye to the brain.
It is characterized by a sudden onset of total or partial vision loss with a normal ophthalmological examination.

Symptoms of optic neuritis

Optic neuritis can affect one or both eyes. Symptoms may appear suddenly or develop gradually over several days. The most common symptoms are:

Eye pain – Most patients who develop optic neuritis experience eye pain that worsens with eye movement. Sometimes, the pain feels like a dull ache behind the eye.
Vision loss in one eye – Patients experience a temporary reduction in their vision, but the extent of the loss varies. Significant vision loss usually develops within hours or days and improves fully or partially over several weeks or months. Sometimes, vision loss is permanent despite treatment.
A loss of the visual field – Visual field loss can manifest in any form: a loss of central or peripheral vision.
A color vision disorder – Optic neuritis often affects color perception. This is called dyschromatopsia. You may notice that colors appear less vibrant than normal.
Flashing lights – Some people with optic neuritis report seeing blinking or flickering lights when they move their eyes. These are photopsias, not phosphenes (flashes of light triggered by retinal stimulation).

If optic neuritis is not treated, symptoms can worsen.

Uhthoff's phenomenon – Optic neuritis and stress, sport or heat

The symptoms of optic neuritis can worsen when you are hot or very tired.
For example, symptoms may be more pronounced when you exercise or when you take a hot bath.

When should you consult a doctor?

Optic neuritis should be considered a serious neuro-ophthalmological condition. Some cases can lead to permanent vision loss, and others are associated with other serious medical problems. Seek urgent medical attention if you suspect optic neuritis or if:

You develop new symptoms, such as eye pain or a change in your visual acuity.
Your symptoms are worsening or not improving with the prescribed treatment.
You are experiencing unusual symptoms, including vision loss in both eyes, double vision, numbness or weakness in one or more limbs.

Diagnosis of optic neuritis

Optic neuritis is suspected by the ophthalmologist after a complete eye examination, which is most often normal at the onset of symptoms. It is common to say that the patient has poor vision, but the ophthalmologist sees nothing abnormal.

The assessment carried out in the emergency setting generally includes the following examinations:
Visual acuity measurement.
Assessment of eye mobility and investigation of associated heaviness.
Investigation of pupil asymmetry in response to light stimulation.
Clinical examination with a slit lamp to look for an abnormality of the optic nerve: edema or pallor.
OCT imaging of the optic disc: the insertion of the optic nerve into the eye. It can sometimes reveal slight edema.

Outside of an emergency setting, the ophthalmologist will assess the impact of optic neuritis by performing:

Repeated measurements of visual acuity.
A visual field looking for loss of contrast or enlargement of the blind spot.
An angiogram is performed if there is doubt about a differential diagnosis.
A color vision assessment in search of a color recognition disorder (dyschromatopsia) in the red-green axis.

The role of brain MRI

To establish a definitive diagnosis, your ophthalmologist asks the radiologist to perform an MRI of the brain and optic pathways (optic nerve).
The examination will reveal the inflamed area (hypersignal). The optic nerve will be swollen and will appear whiter than the rest of the visual pathways (hypersignal).
An MRI is the gold standard for establishing a definitive diagnosis. You will then be referred to a neurologist to determine the cause and begin treatment.

Causes

The exact cause of optic neuritis is usually unknown. It is thought to develop when the immune system mistakenly targets myelin: the protective substance that covers the main nerves in our body. In the event of an autoimmune attack, inflammation and damage to the myelin occur.
Normally, myelin helps electrical impulses travel quickly from the eye to the brain, where they are converted into visual information. Optic neuritis disrupts this process and affects vision.

Multiple sclerosis (MS)

Multiple sclerosis is a disease in which your autoimmune system attacks the myelin sheath that covers the nerve fibers in your brain.
In people with optic neuritis, the lifetime risk of developing multiple sclerosis after an episode of optic neuritis is approximately 50%.
The risk of developing multiple sclerosis after optic neuritis increases further if an MRI shows lesions in your brain.

Other causes

Neuromyelitis optica – In this disease, inflammation affects the optic nerve and spinal cord. Neuromyelitis optica shares similarities with multiple sclerosis, but it does not damage the brain's nerves as frequently as MS. Nevertheless, the disease is more severe than MS, often resulting in a slower recovery after a relapse than in MS.
Anti-myelin oligodendrocyte glycoprotein (MOG) antibodies – This condition can cause inflammation of the optic nerve, spinal cord, or brain. As with multiple sclerosis (MS) and neuromyelitis optica, recurrent inflammatory attacks may occur. Recovery from MOG attacks is generally better than that from neuromyelitis optica.
Infections – Bacterial infections, including Lyme disease, cat scratch fever and syphilis, or viruses, such as measles, mumps and herpes, can cause optic neuritis.
Systemic autoimmune diseases – Autoimmune diseases that normally rarely attack the eye and brain, such as sarcoidosis, Behçet's disease, and lupus, can cause recurrent optic neuritis.
Drugs and toxins – Certain drugs and toxins have been linked to the development of optic neuritis. Ethambutol, used to treat tuberculosis, and methanol, a common ingredient in antifreeze, paints, and solvents, are associated with optic neuritis.

Risk factors

The risk factors for developing optic neuritis are as follows:

Age – Optic neuritis most often affects young adults between 20 and 40 years old.
Sex – Women are much more likely to develop optic neuritis than men.
Ethnicity – Optic neuritis occurs more often in people of Caucasian origin (white skin)
Genetic mutations – Certain genetic mutations can increase your risk of developing optic neuritis or multiple sclerosis.

Treatment

The treatment of optic neuritis is based on treating the inflammatory flare-up and addressing the underlying cause to prevent recurrences.

Crisis treatment relies on high-dose intravenous injections of steroidal anti-inflammatory drugs (corticosteroids).
The primary treatment is generally based on immunomodulators or immunosuppressants.
These are innovative treatments that allow for targeted regulation of the immune system or for lowering it globally in order to calm disease flare-ups.

Prognosis

Optic neuritis is a serious condition. While many patients recover adequate visual acuity, visual impairment is not uncommon! Profound and debilitating vision loss persists in some patients. Factors associated with a good prognosis include:

Early intervention.
Preserved vision prior to treatment.
A rapid improvement in vision following the first injection of corticosteroids.

The prognosis for optic neuritis is also closely linked to that of the underlying disease. For example, multiple sclerosis can also lead to severe motor disabilities.

Complications

Complications arising from optic neuritis may include:

Irreversible damage to the optic nerve – Most patients will experience permanent and irreversible damage to the optic nerve after an episode of neuritis, but this damage may not cause permanent symptoms.
A decrease in visual acuity – Most people regain normal or near-normal vision within a few months, but some loss of color discrimination may persist. In some people, vision loss persists.
Side effects of treatment – Steroids used to treat optic neuritis weaken your immune system, making your body more susceptible to infections. Other side effects include mood changes and weight gain.

Sources:
https://eyewiki.org/Category:Articles
https://www.cahiers-ophtalmologie.fr/
https://snof.org/
https://couf.fr/