In order to lessen the frequency and severity of their headaches, migraine sufferers are sometimes instructed to wear eyeglasses with precision-tinted lenses. These are known as prescribed precision ophthalmic tints, or POTs. Up until recently, however, the science behind the POTs/headache relationship wasn't clearly understood. Now, a team of scientists have used functional magnetic resonance imaging (fMRI) to gain an understanding of just what is taking place.
Researchers already knew that a certain type of abnormal brain activity, known as hyper-activation, caused migraine sufferers to see intense patterns known as auras. It was also known that wearing glasses, tinted specifically to the needs of each user, helped to prevent this from happening.
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Prof. Jie Huang, of Michigan State University's Department of Radiology, decided to find out why this was the case.
The project began with a group of 11 migraine sufferers each receiving a pair of glasses equipped with an intuitive colorimeter, a device that illuminates text using different colors of light. The test subjects were able to use this in order to determine what color made them feel the most comfortable, by reducing perceptual distortion in the text most effectively. They were then given a pair of glasses tinted to that color, along with two other pairs tinted to grey and another color. Each subject was paired to a non-migraine-suffering control subject, who received a duplicate trio of glasses.
Both the initial subjects and their controls were then placed in an fMRI machine, where they viewed images of high-contrast stripes or gratings using each pair of glasses. Such patterns are known for bringing on migraine headaches. While the migraine sufferers did report 40 percent less discomfort when using the other glasses, that increased to 70 percent when they used the POTs.
The fMRI showed that those glasses worked by reducing hyper-activation in the visual cortex of the brain - specifically, in visual area V2.
"The specific characteristics of activation we recorded could provide a potential biomarker for identifying those migraine patients suffering visual cortical hyper-activation," said Huang. "This biomarker could prove useful not only for further evaluation of tinted lenses but also for studying the effectiveness of drugs to prevent migraine headaches."