Staring at a screen for more than eight hours a day does terrible things to our eyes — so much that scientists have introduced a whole new spectrum of complications called Computer Vision Syndrome. Now, scientists in Japan say they've proven one more consequence: dry eyes.

Before you get too worried, know that dry eyes is not the worst thing ever. The main sign is a decrease in the mucus that coats our eyes and keeps them protected and moist. In the very worst cases of chronic dry eye — a problematic disease — infections and scarring are more common, and discomfort is a daily irritation. If you've ever felt your eyes dry out on a plane or in an air conditioned room, you've experienced it.

In the new study, published in JAMA Ophthalmology earlier this month, researchers showed that the more time people spent looking at computer screens the less their eyelids produced a protein called MUC5AC. According to Reuters, the protein is a component of the "tear film" secreted from the cells of the upper eyelid. "The data obtained in the present study suggest that office workers with prolonged (screen) use, as well as those with an increased frequency of eye strain, have a low MUC5AC concentration in their tears," the researchers wrote.

People unaffected by dry eyes have about 8.2 nanograms of MUC5AC per milligram of tear film, Those with dry eye disease have 3.5. After examining the mucus secretions and screen gazing of 96 Japanese test subjects, people who looked at screens an average of eight hours a day secreted about 6.8 nanograms. Those who looked at screens the least, secreted more of the protein.

"Mucin is one of the most important components of the tear film," Dr. Yuichi Hori, who was not a part of the new study, told Reuters by email. "Mucins (including MUC5AC) function to hold water on the ocular surface of the epithelia that synthesize them, hence, they are major players in maintenance of the tear film on the ocular surface."

Of course, there are other problems with looking at screens, which affect between 50 percent and 90 percent of people who use computers all the time. Neck pain, eye strain, headaches, neck aches, light sensitivity, double vision — all are symptoms of Computer Vision Syndrome. In one severe instance, a 26-year-old Chinese man had reportedly spent too much time texting his girlfriend at night and suffered a detached retina, which required surgery. The new study also comes just weeks after a warning from eye doctors that Google Glass was causing eye muscle strain.

To avoid all of these problems, doctors recommend fairly simple solutions: Blink more often, and take breaks from the screen by staring at least 20 feet into the distance. And don't text your girlfriend all night, dude. She needs her space.

Source: Y. Uchino, Uchino M, Yokoi N, et al. Alteration of Tear Mucin 5AC in Office Workers Using Visual Display Terminals. JAMA Ophthalmology. 2014.