COMPUTER VISION SYNDROME
According to a survey of 1,307 U.S. optometrists published in the Journal of the American Optometric Association, an estimated 10 million Americans visit eye specialists each year for VDT-related vision problems. Workers afflicted with what one glare-filter manufacturer has termed 'computer vision syndrome' (CVS) far outnumber the victims of more widely publicized video display terminal (VDT)-related traumas such as carpal tunnel syndrome. Dr. James Sheedy, associate clinical professor of optometry at the University of California at Berkeley's School of Optometry and chief of the university's VDT Eye Clinic, calls vision problems the most frequent health complaint among VDT workers.
Any type of close-up work that entails staring at a fixed point for hours takes its toll on the eyes. However, VDT work is particularly demanding. Students poring over textbooks and drafters working on a design can change positions periodically for optimum comfort and lighting. The terminal user doesn't have that option. For most of us, the monitor remains in one spot at a fixed distance from the eyes, creating such unique irritants as glare and flicker.
The ABCs of CVS
Eyestrain, headaches, blurred vision, dry or irritated eyes, neck or back aches, photophobia (unusual sensitivity to light), double vision, and afterimages are the most common side effects of extended VDT work. Other symptoms include blurred distance vision, crossed eyes, and-in some cases-the 'McCullogh effect,' in which white objects appear pink after using a VDT (This usually clears up within minutes).
Optometrists attribute CVS symptoms among nearly 40% of their VDT-using patients to environmental factors: lighting, poor screen resolution, glare, and so forth. To that list, we can add such contributing factors as poor workstation design and extended hours of uninterrupted terminal time.
Flicker can also be a significant cause of eye fatigue among computer users. Most cathode ray tube (CRT) monitors repaint the screen 60 times per second (or 60 Hz) which is generally considered the minimum acceptable refresh rate. Many users argue that even this level produces a noticeable flicker that contributes to eyestrain. For this reason, most new video boards and monitors support at least 70-Hz refresh rates. If monitor flicker bothers you, check the specs on your monitor and graphics board. They may already be able to do 70 Hz or better, and a simple setup change can produce a more stable image. Otherwise, consider upgrading to a graphics board and monitor that support higher refresh rates.
Fortunately, current research indicates that most VDT-related vision problems are short-term and can be alleviated or reduced by a change in work habits and office setup. Optometrists and others also recommend routine eye examinations for anyone who uses a computer regularly. When possible, see an eye specialist who is familiar with VDT-related problems, and make sure you provide your doctor with a detailed description of your job and your work environment. Often, something as simple as changing the position of your monitor or reducing office lighting can go a long way toward alleviating VDT-related vision problems.
In extreme cases (as with many types of long-term close-up work) extended VDT use can bring on myopia or nearsightedness, which can be helped only with prescription lenses. Bifocal wearers often suffer neck strain or backaches at terminals because their glasses are usually designed for a distance and angle of vision incompatible with using a computer. Options in such cases include a separate prescription for computer use or a continuous-curve bifocal lens that can adjust to all demands.
The Filter Solution
But prescription glasses and workstation adjustments don't always do the trick. In these instances, a glare filter can be a simple and effective way to fight eye fatigue. Not only do these filters reduce eyeball- bending glare-some also claim to make flicker less perceptible. Glare filters come in three basic varieties: Mesh, glass, and plastic. All filters darken the screen, but glass and plastic units usually make up for this with enhanced contrast. Most eye specialists recommend glass filters, since they tend to distort the image far less than mesh varieties, which can produce a moire pattern on screen (an interference pattern referred to as 'the screen door effect').
Glass and plastic filters have two drawbacks, though: They're more expensive and more reflective than mesh, so in extreme lighting, the filter may produce more reflections than the naked monitor. Casual users, people who don't want to spend much for a product, or users in harsh lighting conditions should consider mesh.
The only way to know if a filter will meet your needs is to work with it on your computer for a few days. To help consumers make a more educated decision, the American Optometric Association (AOA) has begun a Seal of Certification and Acceptance program to judge the effectiveness of filters. So far only one company, Optical Coating Laboratory, Incorporated (OCLI), has submitted its products for review. All the OCLI filters have received the AOA seal.
Virtually every filter manufacturer offers both mesh and glass products. Along with reducing glare, some filters are supposed to cut static, which means they prevent charged dust particles from collecting on the surface of the monitor. Others claim to block potentially harmful electromagnetic emissions. However, filters cannot block rays from the back of monitors, the greatest source of low-frequency emissions.
The big question is: Do filters work? Many users report reduced glare and, often, reduced eye fatigue after installing their filters. With an effective filter, users can work at a terminal all day with virtually no eyestrain and without having to position the monitor away from the sun's path. And you couldn't ask for an easier product to install. Filters come in three basic designs: They attach directly to the front of your monitor, hang from the top, or fit like a glove over the bezel. The latter, so-called contour models may be the best choice if you have a monitor with a curved bezel, because they can block light coming in from the sides.
However, all is not rosy. Filters create problems, particularly their noticeable darkening of the screen. Some screens look flatter and darker, as if you were wearing sunglasses. Although making the adjustment can be difficult at first, most users feel they can live with the results simply by adjusting the monitor's brightness and contrast.
Prices of filters vary considerably. Except for a few extreme cases (in which individuals sit adjacent to large windows, for example), low-price units seemed to be as effective as their more expensive counterparts. Regardless of what type of filter most users install-mesh or glass, inexpensive or pricey-few people remove or return them, which is probably the strongest recommendation of all.
Give Your Eyes a Break
You can also alleviate the symptoms of computer vision syndrome by taking 'eye breaks' every 30 minutes or so for some basic relaxation exercises:
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Cup your hands and place them over your eyes for 60 seconds. This will lower the pressure on your eyeballs.
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Roll your eyes slowly three or four times clockwise, then reverse direction.
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Gaze at an object at least 20 feet away. Changing the field of vision forces your eyes to readjust, relieving the stiffness and tension caused by maintaining a short, fixed focus for too long.
Another suggestion: Blink deliberately and frequently to cleanse your eyes and minimize the annoying itch created by eye fatigue.
Helping the Cause
Eye doctors are spearheading the battle against CVS. Some are prescribing computer screen filters or setting up mock VDT workstations in their offices to help diagnose patients. A few specialists have opened VDT vision clinics.
More and more employers are doing their part to alleviate VDT-related vision problems. 'Companies are recognizing that this is not a real costly benefit,' says American Optometric Association spokesperson Charlotte Rancilio, 'and it's going to help people on the job.' Nearly every business supports ergonomic furniture and workstation design-and some firms are picking up the tab for special VDT vision exams. 'You can't count on employees to self-diagnose,' notes Dr. Sheedy of the UC Berkeley VDT Eye Clinic.
'The employer has to be involved to some extent.'
That's far-seeing advice for every agency.
NOT FOR YOUR EYES ONLY
According to The American Optometric Association survey, the major environmental causes of VDT-related eye problems are all readily correctable. These common-sense adjustments to your workstation and work habits can work wonders:
- Check for flicker. This can be one of the primary causes of eye fatigue. If you notice a flicker on your display, you may need to upgrade your graphics card or monitor to support a higher refresh rate (The PC graphics community recommends using a monitor with a minimum refresh rate of 70 Hz).
- Adjust the height of your monitor for optimum comfort and minimum strain, so the top of the screen is at eye level.
- Keep your distance. Although the most comfortable viewing distance varies, eye care specialists generally recommend sitting 18 to 24 inches away from the screen. If you need to sit closer to see the text, visit your eye doctor; you may need special VDT glasses.
- Control harsh lighting. Position your monitor so light hits it from an angle. Avoid having any direct light source (such as a lamp or window) either behind you when looking at the screen or directly behind the monitor itself. When possible, reduce overhead lighting by either turning off some lights or removing every other bulb from fluorescent light fixtures.
- Don't go overboard on resolution. Running your monitor at higher resolutions makes for extremely small type that can be difficult to read. Consider dropping your monitor's resolution down a notch to allow easier reading.
- Take regular breaks. Look away from the screen for five or ten seconds every ten minutes or so. Eye specialists recommend taking a five or ten-minute break after every two hours of continuous computer use. Do some paperwork, take a walk, and give your eyes a chance to focus on distant objects. The time away from your desk will do your eyes, and your blood pressure, some good.