When temporary vision loss in one eye isn't a sign of stroke

It's enough that migraines often involve awful symptoms such as nausea, vomiting, fatigue, and brain fog. But a slice of the 40 million Americans who cope with these recurring, throbbing headaches also experience something else: temporary blindness or other visual disturbances in just one eye.

Known as retinal migraines, these visual events arise gradually, last from 10 minutes to an hour, and arrive along with or shortly after the start of the headache itself, which can last for four hours to three days. An estimated one in 200 migraine sufferers also experiences the retinal version, which occurs three times as often in women as men. After each episode, eyesight returns to normal.

But while retinal migraines aren't dangerous, their dramatic symptoms might seem suspiciously similar to what can happen during a stroke. Stroke-related vision changes differ in one important way, however: they appear abruptly, says Dr. Amanda Macone, a neurologist and headache medicine specialist at Harvard-affiliated Beth Israel Deaconess Medical Center.

"Instead of a gradual progression, visual symptoms during a stroke happen all of a sudden," she says. "And often those symptoms include a complete loss of vision. It's like a black curtain suddenly sweeping across your visual field."

Baffling distinctions

Scientists aren't sure what triggers retinal migraines. But they may be linked to brief changes in nerves or blood vessels leading to the retina, the light-sensitive tissue at the back of the eye.

Retinal migraines also share some of the same characteristics as a visual migraine aura, which includes features such as flashing lights, dots in the visual field, and other vision changes — but in both eyes. "Sometimes people describe retinal migraine as a fuzzy line going across their vision, or as pure blindness or blind spots," Dr. Macone says. "It's a phenomenon we see much less often than visual aura."

Keeping track of these possible vision disturbances — and how they might apply to you — can be confusing.

"See a doctor if this is happening for the first time or if your vision loss is sudden, and especially if you have other symptoms associated with it," Dr. Macone says. "If you have abrupt sensory changes, an inability to move your arm or leg, or changes in speech, then it's absolutely crucial to get evaluated immediately in the emergency room."

Image: © JGI/Jamie Grill/Getty Images