Scientists may have found why many migraine sufferers are sensitive to light. Specialised nerve cells in the eye appear to trigger migraine headaches even in people who are registered blind.
About 85 per cent of migraine sufferers are "photophobic", meaning they react badly to light. Scientists studied photophobia in two groups of blind people. One was unable to detect light, while the other, though legally blind and unable to discern images, could detect light and was susceptible to photophobia.
"While the patients in the first group did not experience worsening of their headaches from light exposure, the patients in the second group described intensified pain when they were exposed to light, in particular blue or grey wavelengths," said Professor Rami Burstein of Harvard Medical School, who led the study, published in Nature Neuroscience.
The scientists found that specialised cells in the retina of the eye, called melanopsin photoreceptors, are involved in sending signals to the brain along the optic nerve. These cells can trigger migraine headaches and are the only functioning light-sensitive cells left in the people who are partially blind.