Optic neuritis (ON) is an inflammatory and demyelinating eye condition that causes eye pain and temporary vision loss. ON is the first sign of multiple sclerosis (MS) in about 15 percent to 20 percent of people with MS, regardless of the type of MS they have. About half of all people with MS will develop ON in their lifetimes.

People who are Caucasian or who live in high-altitude areas are at a higher risk of developing ON. Similar to MS, ON affects more women than men, and symptoms typically appear in people who are between 20 and 40 years old.

One MyMSTeam member shared their story with ON and an MS diagnosis: “After having headaches and eye pain for seven days, I went to see my ophthalmologist. He said I had optic neuritis. Then, I saw a neurologist the next week, and he diagnosed me with multiple sclerosis. I remember those first weeks being very grueling and exhausting.”

What Causes Optic Neuritis?

The cause of ON is not well understood. Researchers believe ON may be caused by an inflammatory response from certain bacterial infections, viral infections, or autoimmune diseases such as MS. ON is also associated with a rare eye condition called neuromyelitis optica, which also affects the spinal cord.

In MS, the immune system attacks the myelin, a protective coating that surrounds the nerves within the central nervous system (brain and spinal cord). The optic nerve sends signals from the eyes to the brain, allowing people to make sense of what they see. If the optic nerve becomes inflamed, it cannot send signals to the brain effectively. Within a couple of days, an individual may not be able to interpret visual images clearly or may experience vision loss.

Symptoms of Optic Neuritis

ON symptoms typically happen suddenly. They can cause blind spots (scotomas) or areas of poor vision in one or both eyes. Symptoms vary depending on the severity of optic nerve damage, but vision loss is typically the main symptom.

Other symptoms include:

• Double vision (diplopia)
• Blurred vision
• Eye pain with eye movement in one or both eyes
• Involuntary movement of the eyes (nystagmus)
• Pain in the back of the eye socket
• Decreased visual field
• Deficiency or loss of color vision (dyschromatopsia)
• Flashes of light or floaters (photopsia)
• Pupil abnormalities (shape, size, and reaction to light)
• Thinning of the retinal nerve fiber layer
• Swelling of the optic disc

Symptoms of ON can vary widely, and even severe symptoms can resolve over time. It’s also possible to have swelling or inflammation of the optic nerve without it ever affecting a person’s vision.

If you begin to experience eye problems, specifically double vision or nystagmus, see an ophthalmologist, neurologist, or neuro-ophthalmologist right away.

Diagnosing Optic Neuritis

It’s important to have routine eye exams to help pinpoint potential ON, even if you’re not experiencing symptoms. Your doctor may perform the following tests.

Funduscopic or Ophthalmoscopic Exam

An ophthalmoscopic eye exam allows the doctor to evaluate the optic disc in the back of the eye. The optic disc is where the optic nerve enters the retina. About one-third of people with ON have swelling in their optic disc.

Pupillary Light Reaction Test

A pupillary light reaction test can be used to observe pupillary responses to bright light, as well as pupil size and shape. Pupillary response abnormalities are a common symptom of ON. Pupils typically will not constrict (get smaller) when exposed to bright light. This phenomenon is called relevant afferent pupillary defect, or Marcus Gunn pupil.

Other Tests

Other tests to diagnose ON might include:

• Blood tests to check for infections
• An MRI of the brain to check for lesions
• Optical coherence tomography testing to measure retina thickness
• Visual field tests to measure peripheral vision
• Visual evoked response testing to examine electrical signals sent to the brain

Treating Optic Neuritis

If ON symptoms are mild, the condition typically can improve on its own. However, if symptoms are severe or begin to interfere with daily activities, treatment can help ease symptoms, improve vision, or slow down the progression of the disease.

The most effective treatment to improve visual problems in ON involves steroids (corticosteroids). Steroid treatment can help reduce inflammation and prevent optic nerve damage. Steroids — such as methylprednisolone (Solu-Medrol) — are typically administered intravenously at first, followed by a course of oral steroids (prednisone). Studies have found that low-dose oral prednisone alone is not effective for treating ON. In fact, it may actually increase the risk of ON episodes.

The majority of people diagnosed with ON recover well. About 80 percent of people report improvement in their vision within two or three weeks from their first symptoms.

Therapeutic plasma exchange (TPE), also called plasmapheresis, is another treatment option if steroid treatment is not effective. In some diseases and autoimmune conditions such as MS, blood plasma can carry a substance that triggers disease symptoms. TPE helps to remove this substance from blood plasma — and possibly reduce ON symptoms in the process.

Living With Optic Neuritis and MS

People with MS may experience flare-ups or relapses of ON that affect one or both optic nerves. Some ON side effects, such as diplopia and nystagmus, can affect a person’s sense of balance and increase safety risks for people with MS.

Most people with ON and MS tend to recover and regain their vision within a few weeks or months. However, some people need up to a year to recover. Some ways to help reduce accidents when experiencing ON include:

• Using a cane or mobility aid when walking
• Carrying a flashlight when you go out at night
• Organizing your things at home, school, or work so they are easy to find
• Making sure home or work areas are lit well
• Marking light switches, doorways, and steps with paint or colored tape
• Using a large-print version or requesting large print for books, magazines, newspapers, telephone dials, or calendars
• Using other low-vision aids, such as magnifiers and talking watches

In addition, wearing an eye patch on the affected eye can help reduce double vision without delaying your recovery or affecting your vision. “I was flying back home by myself and having trouble with double vision. I wore an eye patch, and it worked great,” said one MyMSTeam member. Another wrote, “My doctor said I could wear an eye patch for short periods of time. It helped me feel less nauseous since the vision loss was so sudden.”

Talk With Others Who Understand

MyMSTeam is the social network for people with MS and their loved ones. Here, more than 185,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Have you experienced an episode of optic neuritis? Share your experience in the comments below, or start a conversation by posting on MyMSTeam.