Most Americans sit for at least six hours a day—an act that has been linked to obesity and heart disease, among other ailments. Mounting evidence suggests long hours staring at computer monitors may also be taking a toll on the eyes. People peering for hours into a screen tend to blink less often and have tears that evaporate more quickly, which dries out the eye and can cause blurred vision or pain. Left untreated, dry eye can lead to corneal ulcers and scarring.

Tears keep the eye moist and wash away dust or debris that could cause damage. But the tears of people with dry eye have less of a protein called mucin 5AC, which normally helps to keep tears sticky and spread evenly across the eye. A new study, based on 96 Japanese office workers, found that staring at a screen for eight hours or more is associated with lower mucin levels. The results were published online in June in JAMA Ophthalmology.

The good news is that the damage from staring at a screen is not likely to be permanent. Certain molecules that help to produce mucin remained roughly equal among test subjects with and without dry eye, regardless of their eyestrain status. Although larger studies need to be done, the findings confirm mucin as a possible target for future diagnosis and treatments of dry eye disease. Doctors already suggest taking regular breaks from the screen. Take a walk—or you may have a reason to tear up.