Do Your Eyes Hurt Now?

Millions of Americans spend hours each day on the job and at home with their eyes locked on a computer video display terminal (VDT). Talk about eyestrain!

There is no convincing scientific evidence that VDTs are harmful to the eyes. However, as many computer users know from experience, staring at a computer screen for hours at a time can cause red, watery or dry eyes, blurred vision, and difficulty in focusing, headaches, strain and fatigue.

"It's like watching TV for eight hours a day," says Richard Lee, an Oakland, Calif., ophthalmologist and spokesman for the American Academy of Ophthalmology. "You would expect your eyes to be very tired. That's what you're doing working in front of a computer," Lee says. "Your eyes are locked in one position."

In 1984 only 25 percent of the U.S. population used computers at work. In 1993 more than 45 percent of the population used computers at work and the number continues to grow, according to the latest statistics from the federal Occupational Safety and Health Administration (OSHA). Also, more than 18 million workers are in jobs that often require intensive keying.

Testing in government laboratories has established that VDTs emit little or no harmful ionizing radiation (such as x-ray) or non-ionizing radiation (such as ultraviolet) under normal operating conditions. In fact, the amount of ultraviolet radiation produced by VDTs is a small fraction of that produced by fluorescent lighting, according to OSHA.

However, research shows VDTs can have potential health effects, with vision problems being the most frequently reported complaint. A study by The National Institute for Occupational Safety and Health, a research arm of the Centers for Disease Control and Prevention, found that more than half of VDT users occasionally experience eyestrain.

Though eyestrain is uncomfortable, it does not mean that continuing to work on a VDT will damage your eyes, Lee says.

"Basically, it's an issue of being able to see the computer screen clearly and just ergonomics," Lee says. That is, the type of equipment, your workstation design, contrast and glare on a VDT screen, and lighting matter.

Some people will notice that black and white objects appear tinged with color after looking at VDTs for an hour or more. These colors are usually complementary (opposite) to the color of the VDT characters, and are not a sign of an eye disease, damage to the eye or eyestrain, according to the American Academy of Ophthalmology. Lee says what happens is that the photoreceptors within the retina, which record images, get oversaturated.

Because most of us have to work with VDTs, what can be done to prevent eyestrain and other visual discomfort? The American Academy of Ophthalmology and OSHA offer these tips:

1. Take a break from looking at the computer monitor. OSHA recommends a 10-minute rest break after two hours of continuous VDT work for operators under moderate visual demands and a 15-minute rest break after one hour of continuous VDT work, which involves a high visual demand or repetitive work task. "Breaks vary for the individual," Lee says. "Yet, even looking away from the monitor or closing your eyes every 20 or 30 minutes can provide some relief."
2. Make sure you have proper positioning of the display screen. Most new VDTs have separate, adjustable keyboards and display screens that allow both the keyboard and display screen to be positioned appropriately for the employee. Screens should also have user controls for brightness. Screens that swivel horizontally and tilt or elevate vertically enable the operator to select the best viewing angle. The topmost line of the screen should not be higher than the user's eyes. The preferred viewing distance for VDTs range between 18 inches and 24 inches.
3. Lighting should be arranged to avoid reflections and glare on the display screen. Sometimes standard office lighting is too bright for comfortable VDT use. If this is the case, you may install a screen glare filter that attaches directly to the surface of a VDT screen. These should be used as a last resort since filters can reduce visibility and legibility of the screen.

Lee says light tints in eyeglasses or an antiglare coating may also work for some computer users.

Many aging baby-boomer computer users may find it hard to focus in front of a computer monitor. The problem, Lee explains, is presbyopia, a focusing deficit developed by people in their late 30s or early 40s, and virtually everyone older than age 45. Reading glasses correct the condition. However, glasses prescribed for normal reading distances (usually 14 inches to 16 inches) may not be effective for the distance to the monitor screen (18 inches to 24 inches). As a result, bifocal wearers often wind up tilting their heads to focus better.

If you wear glasses, Lee suggests telling your eye doctor or optician about computer use when you are fitted for new glasses. Some adjustments, he says, can be made.

OSHA has several publications about safety and video display terminals. To view one online, visit www.osha-slc.gov/.

Test your vision. Check out Prevent Blindness America - America's online eye tests for children and for adults at www.preventblindness.org.

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External Sources Prevent Blindness America Occupational Safety and Health Administration

This article was reviewed June 2006, by Dennis C. Policastro, M.D., FACP, FACEP, Residency Program Director, Internal Medicine, Pennsylvania Hospital, University of Pennsylvania, Philadelphia, PA.

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