Optic neuritis is a condition that affects the eye and your vision, and occurs when the optic nerve is inflamed.
The optic nerve sends messages from your eyes to your brain so that you can interpret visual images. When the optic nerve is irritated and inflamed, it doesn't carry messages to the brain as well, and you can't see clearly.
Optic neuritis can affect your vision and even cause pain. When the nerve fibers become inflamed, the optic nerve can also start to swell. This swelling typically affects one eye, but can affect both at the same time.
Optic neuritis can strike both adults and children. The underlying cause isn't completely understood, but experts believe that a viral infection may prompt the immune system to attack the optic nerve as if it were a foreign invader.
Loss of vision in optic neuritis commonly reaches its maximum effect within a few days and starts improving within four to 12 weeks.
Even if the cause of optic neuritis isn’t always clear, it is a common condition among those who have multiple sclerosis (MS), a progressive, neurologic disorder. Over 60 percent of people who have MS will develop optic neuritis, and often, it's the first sign of MS.
Diminished vision is usually the main symptom of optic neuritis. The following visual difficulties are common:
Trouble distinguishing colors, or noticing that colors aren't as vibrant as usual
Vision that appears blurry—particularly if it occurs after your body temperature has risen—after you've just taken a hot shower or finished a workout, for instance
Inability to see out of one eye
Abnormal reaction of the pupil when exposed to bright light
Pain in the eye, especially when you move it
The symptoms of optic neuritis can vary widely in severity. More extensive optic nerve inflammation leads to more noticeable symptoms.
Just because you experience severe symptoms doesn’t necessarily mean that optic neuritis will never go away. Additionally, not everyone who has optic neuritis has problems with his or her vision. It's possible for the optic nerve to be inflamed without affecting vision. A careful, medical evaluation of the eye can generally pinpoint optic neuritis even in the absence of symptoms.
A doctor can diagnose optic neuritis with these tests:
Thorough medical exam
Evaluating your eyes' response to direct bright light
Testing of visual acuity using the letter chart to see how well you can see
MRI scan of the brain
Testing of the ability to differentiate color
Complete examination of the back of the eye, known as the fundus
More testing may help to determine the underlying cause of the optic neuritis. However, identifying a specific cause isn’t always possible.
In some cases, optic neuritis may not require treatment. After a few weeks, the disorder sometimes goes away on its own and normal vision returns. This is more common in people who don't have another health condition that has obviously triggered the optic neuritis.
Sometimes a doctor may recommend a brief course of steroids, usually given by vein, to help your vision improve more quickly and minimize inflammation and swelling.
You may also need treatment for another health condition if it’s considered the source of your optic neuritis.
If you experience eye pain or any trouble with your vision, you should visit your doctor for an eye exam. If you've already been diagnosed with optic neuritis, call your doctor if your symptoms change, worsen, or just don't get any better.
Since doctors can't always identify the cause of optic neuritis, it's not known how to prevent it.
Taking corticosteroids on a long-term basis can lead to side effects, such as high blood sugar, weight gain, and bone problems, that affect your whole body. Overall, most studies haven't found that corticosteroids lead to better outcomes than allowing the condition to run its course, particularly given the risk for side effects of steroids. In people with certain brain changes seen on MRI, though, intravenous steroids may help prevent future episodes of optic neuritis.
Just because optic neuritis often clears up without treatment doesn't mean that you shouldn’t seek medical advice. If you have optic neuritis, you may actually have another health condition that's causing it. A complete medical examination may help your doctor find other health conditions that can be treated.