Sunglasses offer relief to migraine sufferers

A new study has proved that exposure to light intensifies the pain of a migraine headache.

The light gets converted into a bolt of energy and is transmitted to the brain via the optic nerve, which increases the pain for the migraine sufferer. Other migraine symptoms include nausea, vomiting and fatigue.

The pain is believed to develop when the matter surrounding the brain and central nervous system becomes irritated, which stimulates pain receptors, researchers said in a paper published in the journal Nature Neuroscience.

The irritation triggers the long and painful headaches that cause thousands of lost days' work in the UK each year.

Some 85 per cent of people who suffer migraines are sensitive to light,

and lead researcher Professor Rami Burstein, of the Harvard Medical School, said sufferers should do anything they could to avoid light when having a pain episode.

He said: "Migraine patients may wear sunglasses, even at night. The dimmest of light can make migraine pain worse. Extremely disabling, photophobia prevents patients from routine activities."

The study proved that light increased the effects of migraines by recruiting two groups of people who suffered regular severe headaches.

One group was made up of blind people who suffered migraines and the other of people with standard vision.

Both were exposed to light and the researchers found the group of blind sufferers did not report increased pain.

In the blind patients, the optic nerve did not send messages to the brain like it did in people with regular vision.

The scientists took the ideas to the laboratory, where they performed a series of experiments in an animal model of migraine.

After injecting dyes into the eye, they traced the path of the melanopsin retinal cells through the optic nerve to the brain, where they found a group of neurons that become electrically active during migraine.

"When small electrodes were inserted into these 'migraine neurons', we discovered that light was triggering a flow of electrical signals that was converging on these very cells," Prof Burstein said.

"This increased their activity within seconds."

And even when the light was removed, these neurons remained activated, he added.

"This helps explain why patients say that their headache intensifies within seconds after exposure to light, and improves 20 to 30 minutes after being in the dark," he said.

The discovery provides scientists with a new avenue to follow in addressing the problem of photophobia.

Prof Burstein said: "This research sets the stage for identifying ways to block the pathway so that migraine patients can endure light without pain."