Exposing migraine sufferers to a narrow band of green light can reduce the severity of their crippling headaches, says a new study.
Most migraine and post-traumatic headaches sufferers find their headaches get worse in light, leading them to quit their most basic daily tasks and seek the comfort of darkness.
But a study has found that exposure to pure-wavelength green light significantly reduced their photophobia, or sensitivity to light.
Photophobia is associated with more than 80 per cent of migraine attacks, say the Harvard Medical School researchers whose study is published in Brain.
Although photophobia is not usually as incapacitating as the headache itself, the inability to endure light can be disabling to migraine sufferers, said lead author Professor Rami Burstein.
The study shows that a narrow band of green light exacerbates migraine significantly less than all other colours of light and that at low intensities it can even reduce the headache itself.
The researchers studied the effects of different colours of light on headache in patients without visual impairment, after discovering that only blue light hurts blind migraine patients.
They asked patients undergoing acute migraine attacks to report any change in headache when exposed to different intensities of blue, green, amber and red light.
At high intensity of light, such as in a well-lit office, nearly 80 per cent reported intensification of headache - in all colours but green.
The researchers were surprised to discover that green light actually reduced the pain by about 20 per cent.
To find out why this happened, they measured the magnitude of the electrical signals generated by the retina, in the eye, and the brain cortex of these patients in response to each colour of light.
Green light generated the smallest electrical signals in both the retina and cortex, they said.
Prof Burstein is now working on developing a more affordable light bulb that emits pure, or narrow band wavelength, green light at low intensity, as well as low-cost sunglasses that block all but this narrow band of pure green light.
The current cost of one such light bulb, and the technology for the sunglasses, is astronomical, he said.
