Scientists have been using light therapy for the treatment of sleep and circadian disorders such as insomnia and jet lag. In a recent study of light's effects on the human circadian clock, researchers at the Cornell University Medical College turned to a commercial light source -- a fiber optic blanket from Ohmeda Inc. used to treat newborns for jaundice. The scientists wanted to prove that light directed at parts of the body other than the eyes would have the same effect. They chose the popliteal area, or the back of the knee, for their study, although any place where vasculature is near the surface of the skin would work as well.Ohmeda's BiliBlanket Plus features a remote light source, so subjects receiving light therapy could not feel the heat. "We were looking for [a light source] to put directly against the skin," said Scott Campbell, director of the college's Laboratory of Human Chronobiology. Halogen lamps used in previous seasonal depression treatments generated too much heat. Because the researchers wanted to administer light therapy to half of their subjects and keep the other half untreated as a control, it was important that the light source not get hot. Enter the BiliBlanket Plus. The device consists of a halogen lamp in a vented metal housing, which also contains a small fan to disperse heat generated by the lamp. Illumination from the halogen bulb travels through 2400 optical fibers encased in a 1-m-long flexible plastic tube. The optical fibers terminate in a 10 × 15-cm woven pad about 0.64 cm thick. Because the light source is remote, the fiber optic pad generates no heat, so subjects could not tell whether they were receiving the light treatment. The researchers placed the fiber optic pads behind the subjects' knees and secured them with polyester athletic knee braces. The participants remained seated for three hours in a reclining chair. Tables were positioned over their laps and 3 × 3-m black opaque polyester "skirts" were draped over the tables to the floor. Each fiber optic blanket provided approximately 13,000 lux at a narrow bandwidth (455 to 540 nm). The halogen light was not plugged in for the control group. The researchers reported that the biological clocks of the volunteers who received the fiber optic light treatment were advanced or delayed up to three hours. The results suggest that this form of light therapy will be effective for sleeping or sightless patients. The Cornell team published its findings in a recent issue of Science magazine.