A natural yellowing of the eye lens that absorbs blue light has been linked to sleep disorders in a group of test volunteers, according to a study in the journal Sleep. As this type of lens discoloration worsened with age, so did the risk of insomnia.
In the Danish study, 970 volunteers had their eyes examined by lens autofluorometry, a non-invasive method for determining how much blue light is transmitted into the retina. Blue light is a portion of the visible-light spectrum that influences the normal sleep cycle by helping initiate the release of melatonin in the brain. Melatonin is a hormone that helps signal to the body when it is time to be sleepy or alert.