Of Migraines and Blind Spots

As an occasional sufferer of migraines, my ears perked up when Chris Smith, host of the podcast "The Naked Scientist," started talking about the pain effect bright lights have on a person with a migraine.  The word is photophobia. It is not a fear of light, but a description of eye discomfort in bright light.

There are blind people who have photophobia when they have a migraine. This intrigued some scientists at Beth Israel Deaconess Medical Center.  They conducted a study and found that the only blind people who could experience photophobia were those who could tell night from day.

At the back of the eyeball is the optic nerve, sometimes called the blind spot, which carries information from the eye to the brain.  This information about light is carried to the brain and causes electrical stimulation there. When there is already pain and disturbance in the brain from a migraine, this extra electrical stimulation increases the pain.

Those whose blindness involves damage to the optic nerve not only cannot distinguish light and dark, but have a hard time regulating their nights and days.  Light sets our circadian rhythm - telling our body it is time to sleep or wake.

Maybe you have taken a "blind spot test" before.  Here is one you can perform at night outside. Look at the moon.  Gently cover your left eye and continue to look at the moon with your right eye.  Slowly move your gaze to the left.  You might have to adjust your gaze up or down slightly. Soon you will not see the moon anymore, but just the halo around it.

Each of our eyes has a blind spot, but in each eye it is off center enough that the loss is compensated for by the other eye.  Our brains do a good job in filling in the details and we don't really notice what we are missing.

If you would like to read more about the study, you can find it here.

Now you've heard something interesting.