Hugh Pickens writes writes: "Scientists have looked for explanations as to why certain conditions occur with age, among them memory loss, slower reaction time, insomnia and even depression looking at such suspects as high cholesterol, obesity, heart disease and an inactive lifestyle. Now Laurie Tarkan writes that as eyes age, less and less sunlight gets through the lens to reach key cells in the retina that regulate the body’s circadian rhythm, its internal clock that rallies the body to tackle the day’s demands in the morning and slows it down at night, allowing the body to rest and repair. “Evolution has built this beautiful timekeeping mechanism, but the clock is not absolutely perfect and needs to be nudged every day,” says Dr. David Berson, whose lab at Brown University studies how the eye communicates with the brain. Dr. Patricia Turner, an ophthalmologist who with her husband, Dr. Martin Mainster has written extensively about the effects of the aging eye on health, estimate that by age 45, the photoreceptors of the average adult receive just 50 percent of the light needed to fully stimulate the circadian system, by age 55, it dips to 37 percent, and by age 75, to a mere 17 percent and recommend that people should make an effort to expose themselves to bright sunlight or bright indoor lighting when they cannot get outdoors and have installed skylights and extra fluorescent lights in their own offices to help offset the aging of their own eyes. “In modern society, most of the time we live in a controlled environment under artificial lights, which are 1,000 to 10,000 times dimmer than sunlight and the wrong part of the spectrum,” says Turner. “We believe the effect is huge and that it’s just beginning to be recognized as a problem.""