Q. I recently started a new job that requires I use a computer terminal a few hours each day. I find viewing the screen severely tiring to my eyes, and eventually I feel tired all over. Do you have any recommendations for me?

A. Many people who work at video display terminals have eye complaints. Some problems stem from the VDT itself, while others are related to posture and the stresses associated with VDT work. For example, your "feeling tired all over" probably stems from muscle fatigue from having to change your posture while working at a VDT, the pressures of a new job, or both.

Fortunately, most problems can be improved by changing the way you do your work.

The most common eye complaints of VDT users are eye fatigue, headaches, blurred vision and itching, burning or irritated eyes. These problems also occur after using your eyes a lot in other tasks that require heavy concentration. People more likely to experience these difficulties are those over 40, especially if they do not have adequately corrected vision.

For one thing, you can develop eye strain and irritation simply from not blinking when staring at a VDT screen. This happens especially when scrolling through large documents, when you have a tendency to stop blinking to avoid missing anything. Blinking helps keep the sensitive surface of your eye lubricated and prevents itching, burning and other eye irritation.

An unusual reaction that can occur after working at a VDT with green print on a dark background is the McCullough effect. Although harmless, it can last for days. This visual effect makes white letters look slightly pink. A white sheet of paper held in front of a white wall appears to have a pink fringe around its edges.

Another problem related to eyesight and VDT work sometimes affects people who wear bifocals. With bifocals, objects are best seen when they are at chest level or below, and 12 to 18 inches away. Unfortunately, the VDT is often at face level or higher and farther away, forcing the user to lean over uncomfortably or hold his head at an unnatural angle. This strained position will often cause headaches or neck and shoulder pain.

To improve your eye symptoms at work, try these tips about proper use of a VDT: Sit in a comfortable position, using an adjustable chair if possible. Ideally, position the center of the VDT screen about 20 degrees below the horizontal (about chest level), and about 14 to 20 inches from your eyes. Place reference materials close to the VDT screen and at about the same distance, to avoid frequent head turning and changing of focus. Adjust room lighting so that it is adequate, while avoiding glare on the screen. You may need to attach a small hood to the VDT, or use curtains or flexible desk lamps to reduce glare. Likewise, don't wear light colored clothing if it causes a bothersome reflection on the screen. Don't forget to blink while viewing the screen. If bifocals are making you hold your neck in an unnatural position, try getting glasses with progressive lenses, which allow you to focus at all distances. Take alternate-task breaks, as recommended by the National Institute of Occupational Safety and Health. Perform another task for 15 minutes after every two hours of moderately intense VDT work (viewing the screen up to 60 percent of the time), and after every hour of high-intensity or repetitive work. For eye problems that don't clear up, see your eye doctor.

For a brochure on eye care and VDT use, "VDT User's Guide to Better Vision," send a self-addressed, stamped envelope to the American Optometric Association, Communications Center, 243 N. Lindberg Blvd., St. Louis, Mo. 63141.

Follow-Up: Yawning

At the end of a recent column on yawning, I asked readers to send in their pet theories about this peculiar phenomenon. Here's what I heard.

Several readers said they yawned more with exercise, especially during aerobics classes. Although yawning may have something to do with making your lungs work better, I really can't explain this reaction.

For one reader, a sudden string of yawns seemed to be the first clue to serious internal bleeding from an ulcer. She reasoned that yawning was her body's way of trying to get more oxygen into her bloodstream.

Another reader associated yawning with being hungry or having low blood sugar, since she could stop her yawns with some candy or gum.

Thinking in terms of evolution, a reader suggested that yawning served as a group signal among primitive man to bed down for the night.

Another felt that yawning served as a tension reliever, much like laughing or crying.

And puzzling over the "contagiousness" of yawning, a reader wondered why her dog's yawning made her yawn, but not the other way around.

And some readers said that just writing about yawning made them yawn the entire time.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington.

Consultation is a health education column and is not a substitute for medical advice from your physician. Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.