It’s one of the scariest experiences you’re likely to have—suddenly and for no apparent reason, you see a blank, black area in your vision. Then come black zigzag lines, sparklers, brilliant globes of color or some other sort of light show. Next, these strange visual disturbances start moving to your other eye. You might think you’re losing your vision. But within an hour, the show is over, your vision is back to normal and you feel fine again.

What’s going on?

What you just experienced is the most common symptom of migraine headaches with aura…the aura itself. What’s confusing—and can be scary—is that without the usual head pain that follows, you might be wondering whether there’s something wrong with your vision or, worse, that you’re having some sort of stroke, such as a TIA. One difference: An aura can last anywhere from 15 to 60 minutes…the visual symptoms of a TIA generally last between three and 10 minutes. Here’s what else you need to know…

THE RARE TYPE OF MIGRAINE

It’s relatively common for migraine sufferers to experience an aura an hour or so before their head pain starts, and nearly all of the time it’s the type of visual disturbance described above, says headache specialist Nada Hindiyeh, MD, of Stanford University. But these two phases don’t always occur in every migraine episode.

Various studies have found that people who have “migraine with aura” experience an aura with no subsequent headache between 37% and 44% of the time. Among people with no history of migraine, it’s estimated that about 13% have experienced aura alone. This can happen to anyone of any age, but it does seem to happen more often among people over age 50, primarily in those with a history of migraine with aura in their younger years but also, to a lesser extent, in some people who never had this type of head pain. Because it seemed as though only the eyes were affected, these events used to be called “ocular migraines,” but Dr. Hindiyeh says that’s a misnomer because the aura still originates within the brain, not within the eyes.

IF THIS HAPPENS TO YOU

If this was your first aura. Call your primary care doctor and describe your symptoms. He/she may want to see you to officially rule out more serious causes of visual disturbance, such as retinal disease, or confirm that you didn’t have a stroke or TIA. If you have any sudden changes such as sudden weakness or numbness, especially on one side of the body, sudden confusion or sudden lack of coordination, immediately seek emergency care.

Look for a pattern. People with painful migraines typically keep a journal to spot any possible triggers such as a food or even bright lights. Even if you’re not getting any head pain, keeping a journal will let you see any pattern to your auras and any subsequent changes in your pattern—from what the visual disturbances themselves look like to how long they last. If an aura lasts longer than your normal pattern, call your health-care provider. Important:  If you also experience new symptoms, such as sudden loss of vision or weakness or numbness on one side of your body, call 911. These can be signs of a stroke.

HOW TO WAIT OUT AN AURA

Although you may not be debilitated like you would if you had migraine pain, it’s important to take safety measures as soon as you notice that your vision has been affected by migraine aura. For instance, if you’re driving, pull off the road.

And because an aura can be stressful even though you know that it’s not dangerous, you might want to practice your favorite relaxation method until it subsides.