What Do Pirates and Migraine Sufferers Have in Common?
Pirates wore eyepatches not because they had all lost an eye. They did so as a defensive mechanism. When you are in a bright environment and go suddenly into the dark, it takes a while to be able to see. Pirates would patch one eye so that when they were relaxing in the ship's hold by candlelight or lamplight and suddenly were called up to the decks to fight off intruders, they would be able to see well enough to fight their intended targets. By keeping one eye "in the dark" with a patch, they were always at the ready. (This historical myth has been deemed "plausible" by Mythbusters.)
So what does this have to do with migraine? Migraine sufferers experience photophobia, or the avoidance of light. Specifically, however, most migraine sufferers avoid bright light when they have a migraine headache because exposure to light makes the headache worse.
Why might this be? Dr. Rami Burstein has presented his recent research into this today at the American Headache Society 52nd Annual Scientific Meeting. To really track down this phenomenon, Dr. Burstein studied blind migraine sufferers. The first group studied were migraine sufferers who were totally blind, with no perception of light. Some of these people will still develop migraine aura, and "see" visual images, because these come from the brain. It is, in fact, the only time they are able to see anything. When observed during a migraine aura, their pupils were noted to constrict in response. The second group studied was a group of migraine sufferers who were unable to see visual images but who could still see light. This group included both migraine with aura and migraine without aura, and who had blindness due to a variety of conditions affecting the retina or other parts of the eye. In this group, the effects of light were either unpleasant, or had no effect—unless they were in the midst of a migraine. There was intensification of migraine pain in all with exposure to light. But what was most interesting—and most "pirate-like"—was that there was a long-lasting effect of light exposure. Exposure to light worsened migraine headache pain within 1 to 5 minutes. Retreating to a dark environment to obtain relief took from 5 minutes to an hour. This occurs in sighted persons as well; it was studied in the blind to exclude interference of other visual input.
Dr. Burstein reported a newly identified visual processing pathway from the retina to the thalamus that accounts for this phenomenon. Blogging live from Los Angeles at the American Headache Society meeting.