Your eyes do more than see.
Researchers at Harvard Medical School demonstrated this by showing that your eyes are part of a light reception system that can keep you alert when sleep starts to fog your brain. When the researchers exposed people to blue light at night, this system immediately increased their alertness and performance on tests.

“These findings add to a growing body of evidence that a novel light reception system exists in the human eye in addition to sight,” says Steven Lockley, an assistant professor at Harvard Medical School and a researcher in sleep medicine at Brigham and Women’s Hospital in Boston. “Men and women exposed to blue light sustained a high level of alertness during the night when people feel most sleepy. These results suggest that light may be a powerful countermeasure for the negative effects of fatigue for people who work or study at night.”

It’s well known that white light can do the same. Long-distance travelers and shift workers sit in front of commercial light boxes that shift their natural clocks with glaring white light, hyping their attention to daylight levels. Apparently, blue light can do this more effectively.

It is even superior to green light, to which human vision is most sensitive. Sleepy people bathed in blue light for six and a half hours performed better than those lit by an equal amount of green light. They consistently rated themselves as less sleepy, showed quicker reaction times, and had fewer lapses of attention than those exposed to green light.

To Lockley and his colleagues, this is proof that eyes are not just used to see. Our orbs also monitor light for the purpose of setting our biological clocks to a 24-hour day. If clock setting and shifting were done by vision alone, it would be more sensitive to green, not blue, light.

Further proof comes from the responses of totally blind people. Most of these people toss and turn through a lifetime of sleeping problems because light cannot reach their brains to adjust their biological clock each day. But a small number easily adjust to the 24-hour cycle of light and darkness even though they cannot see it because their light detection system remains intact (see Sept. 25, 2003, Gazette).