Eyes Control the Internal Body Clock

Image courtesy of NOAA

Circadian rhythms – they keep our systems in balance and running on a schedule.  Our internal clocks, which control everything from sleep-wake cycles to hormones to appetite, are set according to the amount of light that enters the brain.  Until now, how this happens has largely been a mystery.

Biologists from Johns Hopkins, University of Southern California, and Cornell University have recently discovered that one of the photosensitive cells in the retina, the rods, are responsible for “setting” our internal clocks in low light conditions.

We run our modern lives largely by the clock, from the alarms that startle us out of our slumbers and herald each new workday to the watches and clocks that remind us when it’s time for meals, after-school pick-up and the like.

According to the source of this story, Medical News Today, “The study results are important because they indicate that prolonged exposure to dim or low light at night (such as that in homes and office buildings) can influence mammals’ biological clocks and “throw off” their sleep-wake cycle. Study leader Samer Hattar suggests that “one way people can mitigate this effect is to make sure to get some exposure to bright day light every day. (The exposure to brighter, natural daylight will firmly reset the clocks to a proper asleep-at-night-awake-in-the-day cycle.).

AIn addition to those ubiquitous timekeepers, though, we have internal “clocks” that are part of our biological machinery and which help set our circadian rhythms, regulating everything from our sleep-wake cycles to our appetites and hormone levels. Light coming into our brains via our eyes set those clocks, though no one is sure exactly how this happens.

The study appeared in a recent issue of Nature Neuroscience.

Sleep is vital to many eye conditions, including dark circles under the eyes and health conditions like being overweight.