"These people aren't really blind, they are lying." So stated one journal editor when confronted by an experiment whose results seemed impossible.
The experiment involved clocks. Body clocks. Our internal clocks tend to run a little fast or slow, so if we are deprived of any clues to what time it is, we soon get out of sync with the day-night cycle. It used to be thought that our everyday activities kept our clocks on time, but a series of studies in the 1980s revealed that light is the key. The clincher came in 1986, when Charles Czeisler showed that light could be used to reset people's clocks in the same way that one might reset a watch.
The findings helped explain why many blind people suffer periodic sleep disturbances. Because they cannot detect light, their body clocks go in and out of sync with the day-night cycle. But Czeisler, of Harvard Medical School, knew that the clocks of a few blind individuals ran on time. How was this possible?
Czeisler showed that their clocks were also set by light - and that their eyes were somehow detecting it even though these individuals had no conscious awareness of light. That suggested that our eyes have special light receptors that are quite separate from those we see with, and that must have been overlooked despite centuries of research. "That just blew us away," he says.
After 20 rejections over five years and numerous additional tests to rule out other explanations, Czeisler's paper was published in 1995. Other researchers soon identified the mechanism behind what he had found. We now know there are specialised light-detecting cells in the retina whose signals go to the master clock in the brain, rather than to the visual cortex. In some blind people this system remains unaffected by whatever caused their blindness, allowing their clocks to stay on time.
These discoveries are turning out to have profound implications. It is becoming clear that even dim lights can affect our body clocks, meaning simply having the lights on late at night or staring at a computer screen can disrupt our internal rhythms. What's more, it turns out that blue light has the greatest power to change our clocks, and modern lighting is getting bluer. The potential effects go far beyond the unpleasant, jet-lagged feeling that body-clock disruption can cause. There is growing evidence that continual disruption is linked in the long term to serious illnesses including cancer, heart disease and diabetes. It can even alter the wiring of our brains.
This is one of the most important articles I've read in a long time. Kudos to New Scientist for publishing it. To read the rest of this very important article, click here.