The more that the participants in this study squinted their eyes, the less they blinked. And the less they blinked, the more their eyes ached or burned, and the more they reported sensations of dryness, irritation and tearing.
Just a slight amount of squinting reduced blink rates by half, from 15 blinks a minute to 7.5 blinks a minute.
"People tend to squint when they read a book or a computer display, and that squinting makes the blink rate go way down," said James Sheedy, the study's lead author and a professor of optometry at Ohio State University. "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."
Squinting serves two purposes: It improves eyesight by helping to more clearly define objects that are out of focus. It also cuts down on the brightness from sources of glare. It may be voluntary or involuntary a person working at a computer may not realize that he is squinting.
Dry eye is usually treatable with over-the-counter eye drops. It's rarely a debilitating condition, but it can be irritating and painful.
The results appear in a recent issue of the journal Optometry and Vision Science. Sheedy conducted the study with Ohio State colleagues Sowjanya Gowrisankaran, a graduate student, and John Hayes, a research scientist in optometry.
The researchers asked 10 college students to squint at different levels. All participants had 20/20 vision in both eyes. The researchers attached two tiny electrodes to the lower eyelids of each student. The electrodes were also attached to an electromyogram, a machine that records the electrical activity of muscles. In this case, the researchers
Contact: James Sheedy
Ohio State University