Departments: Ask the Experts
Swanson, Jerry R. M.D.
Jerry W. Swanson, M.D., is a professor of neurology at Mayo Clinic in Rochester, MN. Dr. Swanson is also a Fellow of the American Academy of Neurology.
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Your Questions Answered
Q I recently found out by looking on the Web that my symptoms point to ocular migraines. I have also discovered that flashing lights sometimes bring these on. I am an intensive care unit nurse who believes in not running to doctors for every little thing, but should I be concerned?
DR. JERRY W. SWANSON
A Not necessarily, but here's what you should know. Ocular migraine is a term that usually refers to a condition known as migraine visual aura, which involves episodes of passing visual disturbances, such as bright spots, affecting both eyes. Visual aura usually precedes a migraine headache. However, it may also occur during a headache. In some cases, as with ocular migraine, people experience the symptoms of visual aura without getting a headache. The symptoms of an aura usually begin slowly and last 15 to 30 minutes, although they sometimes persist for up to an hour.
Often, the symptoms of ocular migraine begin near the center of vision as either a bright spot or area of visual loss (called scotoma) that spreads to involve one-quarter or one-half of the visual field. Zigzag lines or other shapes may also appear. For some people, these shapes resemble the walls of a medieval fortress. In fact, the term “fortification spectrum” is used by neurologists to describe it.
A visual aura is thought to be an electrical or chemical wave that spreads over the area of the brain responsible for vision (called spreading depression). It is estimated that visual aura occurs in 20 to 25 percent of people with migraine headaches. However, the frequency of visual aura alone (ocular migraine) is not known because many people who have this as an isolated symptom do not seek medical care. Spreading depression may also affect other areas of the brain, causing other non-visual symptoms. For example, people sometimes experience tingling and prickling sensations in a limb or face if areas of the brain that relate to sensation are involved. Similarly, language disturbances or weakness of one side of the body occurs if corresponding areas of the brain are involved.
Aura is generally harmless. The visual disturbances may temporarily interfere with certain daily activities such as reading or driving, but the condition usually is not considered serious. It has been noted, however, that aura may be associated with a small increased risk of stroke (cerebral infarction) in women. (See “Ask the Experts” from the December 2012/January 2013 issue of Neurology Now for more on this topic: bit.ly/migcardio.) The risk is increased further if a woman with aura takes contraceptives that contain an estrogen compound, or if she is a smoker.
A rare condition that is sometimes confused with ocular migraine is retinal migraine, in which an individual experiences repeated bouts of short-lasting diminished vision or blindness that either precedes or accompanies a headache. A retinal migraine—unlike ocular migraine—will affect only one eye, not both. However, loss of vision in one eye may also be caused by some more serious conditions, so be sure to see an eye specialist if this occurs.