For book lovers who like to read any time and anywhere, personal tablets are the best invention since the printing press. Not only is it easy to store multiple books in one place and carry them everywhere, but they can also be read in the dark, making it easy to polish off that bestseller in bed before you go to sleep. But reading a tablet at night can take its toll.
"Studies have shown that people who stare at a digital screen too long can develop problems such as eye strain, headaches and dry eyes; the American Optometric Association calls it Computer Vision Syndrome," says Bertrand De Silva, MD, the medical director of
St. Jude Sleep Center. "That's true with reading tablets in the dark as well, but there's another potential health problem if you are using it at night."
Tablets—as well as smartphones and computers—emit "blue light" waves, so named because they are in the blue and violet area of the light spectrum. These blue waves can boost alertness and mood, which is great during the day—at night, it's another story. "Blue light can throw off the body's circadian rhythm, the biological cycle that helps people alternate between sleeping and wakefulness during a 24-hour period," Dr. De Silva says. "Studies have shown that exposure to blue light at nighttime can suppress melatonin, the hormone the body needs to govern the sleep cycle. The less melatonin the body has, the less sleep you get. And studies show that lack of sleep can potentially lead to health problems such as heart disease and obesity."
Blue light may also cause long-term problems for your eyes beyond temporary eye strain. Some research says heavy exposure to blue light may carry higher risks for macular degeneration and cataracts.
The first preventive step to take is to cut down on tablet usage at nighttime, ideally powering down a couple of hours before going to sleep. Dr. De Silva also recommends lowering the brightness level on the device's screen to make it easier on the eyes.
It can be easy to lose track of time while browsing on a tablet, so Dr. De Silva suggests setting an alarm on the device to limit exposure. Alarms are also a good reminder of the 20-20-20 rule: "Every 20 minutes, look up from your screen and focus on something 20 feet away for 20 seconds," Dr. De Silva says. "It's a good way to rest your eyes."
"It's tempting to want to curl up in bed at night with your tablet, whether it's scrolling through Facebook or reading a digital book or magazine," he adds. "But according to the Vision Council, an optical industry trade organization, almost 70% of adults in the United States report having digital eye strain, with most people experiencing it between 6 and 9 p.m. If you want to read in bed at night, it may be best to do it the old-fashioned way—with an actual printed book."
For more information about St. Jude Medical Center, click here. For more information on Dr. De Silva, click