Symptom Management

Taking a Closer Look at Optic Neuritis

By Dr. Eugene F. May
Optic neuritis occurs when there is inflammation in either or both optic nerves. Everyone has two optic nerves (one connected to each eye), each of which transmit visual signals from the eye to the brain. The characteristic symptom of optic neuritis is therefore blurred vision (and sometimes even loss of vision) in the affected eye or eyes. There is also very commonly pain behind the eye, which increases with eye movement. Some people notice spots in their vision when they have optic neuritis, and there is often impairment of color vision in the affected eye. The inflammation of optic neuritis resolves on its own, usually during the course of several weeks. The pain of optic neuritis always goes away first, as the inflammation in the optic nerve resolves. Vision usually gets better, too, but more slowly. By far, most people with optic neuritis wind up with normal or near-normal vision after recovering, but not always. Up to 15 percent of people with optic neuritis are left with moderate to severe vision loss in the affected eye(s). Repetitive episodes of optic neuritis are likely to cause progressive vision loss. Almost all people who have had optic neuritis experience some damage to the optic nerve (a condition known as optic atrophy), even if vision recovers.

Studies have shown that treatment of optic neuritis with steroid medication (methylprednisolone, prednisone, or dexamethasone, for example) results in more rapid resolution of the symptoms of optic neuritis, compared to no treatment. It is likely, however, that a person’s ultimate visual outcome after optic neuritis is no different, whether or not they are treated with steroids. Therefore, a decision about whether or not to treat optic neuritis with steroids should be made after a detailed discussion between the affected person and a neurologist or neuro- ophthalmologist. There is reason to think that low or moderate doses of steroid medication for optic neuritis can increase the risk of a recurrence later on, so high doses are generally used. Vision and optic nerve health are measured in a number of different ways, in order to diagnose and monitor optic neuritis. Visual acuity (reading the letters on the wall chart), color vision (usually looking at patterned colored spots and making out numbers), and peripheral vision testing are generally performed at the time of diagnosis, and at subsequent exams, to track progress. The doctor examines the eye, in order to exclude other causes of eye pain and vision loss, and to look in the back of the eye, where the optic nerve enters the back of the eyeball.

In most people with MS, during an optic neuritis relapse, the optic nerve looks normal in the back of the eye, because the inflammation in the optic nerve is usually a few centimeters behind the eyeball (“retrobulbar optic neuritis”). In about a third of people with optic neuritis due to MS, the optic nerve is swollen in the back of the eye, because the inflammation in the optic nerve is right at the junction of the optic nerve and eyeball (anterior optic neuritis).

Once a person recovers from optic neuritis, the appearance of the optic nerve usually becomes pale (optic pallor or optic atrophy) because of damage to the optic nerve, whether or not vision recovery occurs. The swelling and atrophy of the optic nerve can be measured in the eye doctor’s office or MS clinic using a technique called optical
coherence tomography. OCT is a quick and painless way to measure the thickness of optic nerve cells and fibers in the back of the eye using a laser. It is very beneficial in diagnosing optic neuritis, and for tracking the progress of optic nerve damage.

When people with MS develop any visual symptoms, they should get promptly evaluated. If optic neuritis is occurring, a decision needs to be made to treat with steroids or monitor. Importantly, other eye conditions need to be excluded so that appropriate treatment can be provided. Having MS does not protect people from other eye conditions, such as glaucoma and retinal detachments. Only medical professionals can make sure that a correct diagnosis and treatment plan is in place.

Perhaps most importantly, people living with MS should be treated with a disease-modifying medication, to minimize the number of relapses that occur. With treatment of MS, relapse rate is reduced, so the risk of repeat episodes of optic neuritis (and other relapse types) is lowered, thus the risk of permanent vision loss is also lowered. Although optic neuritis can cause persistent visual problems, MS only rarely causes blindness. The best way to avoid that unlikely possibility is to get on and stay on MS treatment.