Optic Neuritis- Inflammation of the Optic Nerve #

Optic neuritis is inflammation of the optic nerve, caused by damage to and loss of the protective sheath (myelin) surrounding this nerve that is so vital for good vision. Demyelinating optic neuritis is another term for this eye condition.

Vision symptoms from optic neuritis can include blurring and blind spots. You also may notice distorted vision, reduced colour vision and pain when you move your eyes. These types of symptoms may precede vision loss due to optic neuritis.

Optic neuropathy more generally describes optic nerve abnormalities or damage, including from causes such as blocked blood flow or toxic exposure.

What Causes Optic Neuritis? #

Optic neuritis usually occurs in adults younger than 45 and affects more women than men. The condition is common in people who have multiple sclerosis (MS), which occurs when the body’s own immune system attacks and destroys protective nerve coverings.

Besides affecting eyesight, related nerve damage in MS can lead to loss of mobility and sensory functions, along with other debilitating conditions.

• Infections such as toxoplasmosis
• Ocular herpes
• Other viral infections
• Sinusitis
• Neurological disorders
• Leber hereditary optic neuropathy, an inherited form of vision loss that affects mostly males in their 20s or 30s
• Nutritional deficiency
• Toxins, including alcohol and tobacco

During an eye exam, your eye doctor will look for signs of optic neuritis by conducting tests to evaluate whether you have reduced vision.

Your eye pressure will be measured, and your pupils will be dilated to provide a better view of the eye’s interior structures, including the optic nerve and retina.

When optic neuritis is present, the pupil always appears abnormal (afferent pupillary defect). This means the pupil actually dilates instead of constricting in the presence of bright light. Depending on the severity of optic neuritis, the optic nerve may appear normal or swollen.

If your optometrist or ophthalmologist suspects you have optic neuritis, a visual field test usually will be performed to determine if you have peripheral vision loss. You also might be referred to a speciality clinic to undergo an MRI of the brain to detect possible underlying causes of optic nerve inflammation.

A person with optic neuritis usually undergoes an MRI of the brain, to look for central nervous system lesions.

Image of the back of a healthy eye, where the optic nerve is located. When the optic nerve is damaged, poor vision results.

Treatments For Optic Neuritis #

Treatment of optic neuritis has changed in recent years, due to a landmark series of studies known as the Optic Neuritis Treatment Trials (ONTT).

In these studies, people with optic neuritis were randomized for treatment with intravenous (IV) steroids, oral steroids or placebo. Afterwards, they were evaluated for several years.

From these studies, researchers learned that treatment with steroids had little effect on the final visual outcome in patients with optic neuritis.

However, patients treated with IV steroids had fewer repeat attacks of optic neuritis than patients treated with oral steroids alone. In fact, those treated with oral steroids alone had a higher risk of repeat attacks of optic neuritis than those treated with placebo.

Even more importantly, patients treated initially with IV steroids had about half the risk of developing MS in two years as patients treated with oral steroids only, or placebo. Of those treated with IV (followed by oral) steroids, 7.5 percent developed MS in the following two years, versus about 16 percent in the other groups.

As a result of the ONTT, eye doctors now treat patients with a combination of IV and oral steroids or monitor the condition without prescribing medical treatment. Use of oral steroids alone is not recommended.

For patients who are medically treated, the regimen typically includes three days of IV steroids, followed by about 11 days of oral steroids.*

Prognosis For Those Who Have Optic Neuritis #

Visual deficits caused by optic neuritis may worsen over a period of about seven days before vision typically stabilizes at that level for three to eight weeks. Gradual vision improvement then may occur.

About 95 percent of people with optic neuritis will recover much of their vision within six months of onset. However, about 19 percent will have a recurrence of optic neuritis in the affected eye, and 17 percent will develop optic neuritis in the other eye within 10 years.**

As mentioned above, sometimes optic neuritis is a precursor to the development of MS, so if you have optic neuritis, your doctor may recommend an MRI. If imaging shows “white matter” lesions indicating damage to myelin in nerve fibres, there is a 56 percent chance of developing MS within 10 years. But even with normal results, a person with optic neuritis has a 22 percent chance of developing MS.