For the first time, researchers have shown why precision-tinted lenses reduce headaches for migraine sufferers, a finding that could help improve treatment options for patients battling the debilitating ailment.
Jie Huang of Michigan State University's Department of Radiology used functional magnetic resonance imaging, or fMRI, to reveal how precision-tinted lenses normalize brain activity in patients with migraine headaches, preventing such attacks.
Huang's research appears in the current edition of the journal Cephalalgia, published by SAGE.
While tinted lenses are increasingly used for migraine sufferers, until now the science behind the effects was unclear. The team led by Huang showed how colored glasses - tuned specifically to each migraine sufferer - work by normalizing the activity in the brain's visual cortex, which is responsible for processing visual information and is located in the back of the brain.
Past research has revealed specific, abnormal brain activity, known as hyper-activation, when migraine sufferers saw intense patterns. The precision-tinted lenses considerably reduce the effect.
As part of the study, researchers focused on specific visual stimuli known to trigger migraines. These patterns, high contrast stripes or gratings, can give the illusion of shape, color and movement, not only triggering migraines but also causing seizures in some photosensitive epileptics.
Participants first were prescribed tinted lenses with an intuitive colorimeter, a device used to illuminate text with different colored lights, creating for each test participant an optimal color of light that led to the greatest comfort by reducing distortion.
Tinted lenses with this optimal color were created and given to each test subject, along with two other sets of tinted lenses without the optimal color. In addition, each patient was paired with a migraine-free control subject, who also was tested with that patient's three sets of lenses.
Once in the fMRI machine, the subjects were exposed to a range of striped patterns while their brain images were acquired. Then the researchers analyzed the effect of the tinted lenses on the activation of the different visual areas of the brain.
Specifically, the tinted lenses decreased hyper-activation for migraine sufferers in visual area V2 of the visual cortex of the brain.
Although patients reported some relief (a 40 percent improvement) using the control lenses, the precision-tinted lenses had a significant effect (70 percent improvement) when viewing the stressful stripes.
"The specific characteristics of activation we recorded could provide a potential biomarker for identifying those migraine patients suffering visual cortical hyper-activation," he said. "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."