Squinting At PCs Poses Eye Risk

The more you squint at a computer screen, the more you may be putting your eyes at risk.

A new study shows the more people squint at a computer screen, the less they blink, and the more they reported symptoms like eye strain, dryness, irritation, and tearing.

Researchers found squinting at a computer screen halves the normal number of times a person blinks per minute, which could lead to an irritating but treatable condition called dry eye.

"People tend to squint when they read a book or a computer display, and that squinting makes the blink rate go way down," says researcher James Sheedy, professor of optometry at Ohio State University, in a news release. "Blinking rewets the eyes. So if your job requires a lot of reading or other visually intense work, you may be blinking far less than normal, which may cause eye strain and dry eye."

Blink Before Continuing

In the study, published in Optometry and Vision Science, researchers had 10 college students with normal vision squint at a computer screen placed two feet in front of them while cameras and electrodes recorded how often they blinked.

In five different tests, researchers measured how often the students blinked while at rest or engaged in deliberate squinting at various increments, from barely squinting to eyes closed about halfway.

The results showed even a slight degree of squinting cut blink rates in half, from about 15 blinks a minute to 7.5 blinks a minute. That rate was cut to just four blinks per minute when the students were squinting at the highest level.

Researchers say squinting serves two purposes: it improves eyesight by defining objects that are out of focus, and it cuts down on brightness from sources of glare.

Squinting often occurs as an involuntary response, and researchers say people working at a computer may not even realize they are squinting. They say more research is needed to determine if involuntary squinting affects blink rates as drastically as voluntary squinting, as measured by this study.

But these results suggest that squinting may increase the risk of eye strain and dry eye. Dry eye is usually treatable with over-the-counter lubricating eye drops.

Sources: Sheedy, J. Optometry and Vision Science, October 2005; vol 82: pp 905-911. News release, Ohio State University.

By Jennifer Warner
Reviewed by Louise Chang, MD
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