Diagnosing and Solving VDT Vision Problems

When Christina Mantel started having problems with her vision recently, it took no great effort for the UC Berkeley senior to figure out the source of her headaches and blurred sight. The trouble had started four months earlier, and four months earlier she had begun working on a computer in the campus library where she has a part-time job.

For Mantel, relief was just around the corner, at the university’s School of Optometry, which recently opened the first eye clinic specializing in problems associated with the use of video display terminals.

A Demand for New Service

The new service grew out of the clinic personnel’s realization that they were seeing increasing numbers of people who “showed greater symptoms than they would in the old office setting,” according to James Sheedy, who is chief of the VDT Eye Clinic. “We wanted to provide a service, plus the school was involved in research in this area,” he said.

He pointed out that with more and more people spending some or all of their working hours in front of VDTs, their discomfort is important not only to them but to their employers, since studies show that employees with VDT-related problems have reduced productivity. Legislation has been proposed in about 20 states, including California, to regulate the construction and use of VDTs.

Sometimes, Sheedy said, problems arise because “the environmental design can be off.” Workers may be bothered by poor lighting, reflections in the screen, inappropriate location of reference material, the wrong glasses or postural problems. “A lot of this is because, unlike a typewriter, a VDT screen makes you look up,” he explained.

Some people have trouble with eye movements and coordination, and in their ability to focus, or are especially sensitive to glare. “With black and white copy that’s no problem. With this (the VDT), which can be a little fuzzy, it puts them over the edge,” Sheedy said, adding that the clinic staff is seeing more visual problems than expected.

In addition to a general eye examination, patients are given a series of special tests to evaluate eye movement and focusing skills, coordination of the eyes, glare sensitivity and other aspects of vision related to performance at a VDT.

Christina Mantel discovered her difficulties were both environmental and visual.

Environmental Factors

Before she came to the clinic, she had filled out a three-page questionnaire that asked for information about her work situation--chair, screen and keyboard height, type of terminal, lighting conditions, symptoms and the like. At the clinic, she sat at a computer station where fourth-year intern Mark Buri adjusted the lighting, chair, keyboard and screen to approximate her work situation at the library, and then showed her how to adjust their positions to lessen the strain on her eyes.

It is important that the VDT worker sit at the proper angle to the screen, looking down a little, rather like a typist, to avoid glare from overhead lights. Generally, Sheedy said, overall office lighting should be lower for VDT operation, but he acknowledged that sometimes this creates difficult situations, especially in offices where more than one kind of work is going on. Localized lighting, like adjustable lamps at each station, will help get around this problem.

Reflected glare on VDT screens is a frequent complaint. Glare guards or hoods over the screen can help, and so can pulling the shades or curtains over windows in the background, and wearing dark rather than light or white clothes, which can reflect on the screen. Turning down the screen is also suggested. “There’s a tendency to think the brighter the better, but that’s not true,” Sheedy said.

Mantel tried on a pair of magenta-tinted glasses intended to deaden the brightness of the green characters on the screen (there are gray lenses for white screens, blue ones for amber) but wasn’t impressed. “Some people are like you, but some really swear by them,” Buri said.

According to Sheedy, some patients find that “there is a sharper image with the glasses. There is not much physiological basis for that, but if a person feels the glasses help, then we will prescribe them.”

The proper positioning of materials is also important. They should be the same distance from the VDT-user’s eyes as the screen, and should be as close to it as possible. Buri recommended that Mantal prop up the cards she works from right in front of the terminal.

Because of the terminal’s middle-range viewing distance and higher field of view, some people who already wear glasses may need a special pair specifically for work at the VDT, Sheedy said.

“Bifocals are designed for people looking down, so lens proportions need to be different,” he said. “If we are giving someone bifocals, we design them at the actual work station, so we get the proportions right.”

Buri said that “about half the people who come in need glasses, but a lot just need education about things like where to put the screen, or taking breaks.”