When you focus on a screen, your blinking drops by more than half

The American Academy of Ophthalmology says people normally blink about 15 times a minute, and only about 5 to 7 times a minute while looking at a computer or other screen. A 1993 study in Japan measured 104 office workers. They blinked 22 times a minute on average when relaxed, 10 times while reading a book, and 7 times while looking at text on a computer screen. Seven is a little over a third of the relaxed rate.

Studies use different methods, so some sources give the resting rate as 15 to 20 times. Even so, they agree on the direction: concentrating on something reduces blinking.

The surface of the eye is covered by a thin layer called the tear film. Each time you blink, the eyelid spreads the tears evenly, old tears drain away, and new ones take their place. When the gaps between blinks get longer, the tears stay exposed to the air longer and evaporate more.

In the same study, people reading a book looked downward, so their eyes were less open. When they looked at a screen straight ahead, their eyes were as wide open as when relaxed. With fewer blinks and more of the eye exposed, eyes dry out more easily in front of a screen. The researchers pointed to this as a reason a screen can dry the eyes more than a book.

The American Academy of Ophthalmology explains that the discomfort from long screen use is temporary and does not permanently damage the eyes. Dryness, blurry vision and watery eyes are common. People often blame blue light, but the small amount of blue light from computer screens has never been shown to harm the eyes. The discomfort is linked to looking for a long time, up close, without blinking.

Blinking on purpose, looking at something far away for about 20 seconds every 20 minutes, and placing the screen a little below eye level can help. If you keep forgetting to blink, a program that reminds you to take short breaks is another option. If the symptoms continue, it is best to have them checked by an eye doctor.