It is not news that light is usually painful to migraine sufferers. According to new research, however, a narrow range of wavelengths can actually ease the pain.
Light-induced pain, dubbed photophobia, is associated with 80 percent of migraine attacks. The need to lock oneself away in a dark room prevents people with migraines from participating fully in life, sometimes for days on end. “It is their inability to endure light that most often disables them," said Harvard Professor Rami Burstein in a statement.
Previous research found that blind migraine patients are sensitive to blue light, but immune to the effects of other colors, inspiring Burstein to study how different colors affect sighted migraine sufferers. He tested this by exposing 69 brave patients to different colored light and asking them to rate the intensity of their headache.
Burstein found that light at both ends of the spectrum was problematic, with 80 percent of people in the trial reporting increased pain when exposed to either red or blue light. The brighter the light, the worse the pain. Amber light was better, but green at a wavelength of 530 nanometers was best of all. Most surprisingly, for 20 percent of participants, moderate intensity green light actually reduced their pain relative to a dark room.
All other colors increased headache pain at all intensities, while soft or intermediate green light on average reduced pain. Noseda et al./Brain.
Burstein stressed to IFLScience that “the findings were personal. Not all patients found green light to be the least painful.” Nevertheless, green benefited more patients than it harmed, unlike other colors.
Burstein added that he had no idea of the evolutionary basis for the effect, saying modestly: “I am only smart enough to study the things I can measure. When I can't, it becomes philosophy.” However, he established that neuronal activity in the thalamus region of rats' brains increases when exposed to all colors of light, other than green.
Ideally, people with migraines might be able to read or work under green light, making use of hours that would otherwise be a frustrating waste. Bulbs that emit at precisely 530 nanometers are used in scientific research and medicine, but Burstein says they are prohibitively expensive for home use. He hopes mass production will make them widely affordable if a market can be demonstrated.
Sadly, he told IFLScience, green filters won't work. “There is a large overlap between photoreceptors [in the eye] that are sensitive to blue and those sensitive to green,” he said. The same is true for red and green. “To ensure that only the green cones are activated, one must stimulate a narrow band on either side of 530 nanometers (+/- 5nm). If you took a broad spectrum light bulb and wrapped a green cellophane around it, the spectrum of light will be around 100 nanometers [wide] and you have little control on the intensity of the light.”
Likewise, sunglasses that exclude all non-green light are possible, but narrowing the range to the exact wavelengths required is currently enormously expensive.
If only this was all it took. Sadly, narrow spectrum green lights are currently very expensive. Sean Locke Photography/Shutterstock
