Computer Vision Syndrome
Computer Glasses
August 24, 2009 | 
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When you work at a computer for any length of time, it’s common to experience blurred vision and other symptoms of computer vision syndrome (CVS). Viewing computer-generated print and images on a screen or monitor for prolonged periods is harder on the eyes than viewing a similar amount of material on the printed pages of a book or magazine. If you’re under age 40, blurred vision during computer use may be due to your eyes being unable to remain accurately focused on your screen for sustained periods. Or you may have a hard time quickly and accurately changing focus, such as when you shift your gaze from your monitor to your keyboard and back again. This problem, called lag of accommodation, can cause eyestrain and headaches — two common symptoms of CVS. If you’re over age 40, the onset of presbyopia — the normal age-related loss of near focusing ability — can make focusing on a computer screen even more difficult, further increasing the risk of eyestrain, headaches and eye fatigue. So what can you do to make your eyes more comfortable and function more efficiently during computer use? Have your eye doctor prescribe specially-designed computer glasses. Customized computer glasses can make a world of difference. These special-purpose glasses are prescribed specifically to reduce eyestrain and give you the most comfortable vision at your computer. I already wear glasses. Do I really need computer glasses? If you already wear prescription eyeglasses or reading glasses, you may be tempted to dismiss the idea of computer glasses. But eyeglasses prescribed for general purpose wearing are often not well-suited for prolonged computer work. Why? When working at a computer, your eyes are generally 20 to 26 inches from your computer screen. This distance is considered the intermediate zone of vision — closer than driving (distance) vision, but farther away than reading (near) vision. Most young people wear eyeglasses to correct their distance vision. Reading glasses are prescribed to correct near vision only. And bifocals prescribed for those over age 40 with presbyopia correct only near and far. None of these eyeglasses are optimized for the intermediate zone of vision used during computer work. Even trifocals and progressive lenses, which do include the correct power for intermediate vision, have only a small portion of the lens dedicated to this area — not nearly a large enough area for comfortable prolonged computer work. Without the appropriate eyewear, computer users can often end up with blurred vision, eyestrain, and headaches — the hallmark symptoms of computer vision syndrome (CVS). Worse still, many people try to compensate for their blurred vision by leaning forward, or by tipping their head to look through the bottom portion of their glasses. These unnatural postures can lead to headaches, neck and shoulder pain, and backaches. Computer glasses reduce errors and increase productivity Are computer glasses worth the extra cost of a second pair of glasses? Yes, they are. Research has shown that, in addition to increasing comfort and decreasing the risk of CVS, prescription computer glasses can reduce errors and losses of productivity caused by vision problems during computer work. A study conducted at the University of Alabama School of Optometry found that even minor changes from the optimum lens power for computer work can cause a 38% decrease in accuracy for tasks performed on a computer and a 9% loss in worker productivity. The researchers concluded that, because of productivity gains from workers wearing computer glasses, companies that pay for computer eyewear for their employees could experience a benefit/cost ratio of $18 for every $1 spent. Computer lens designs There are a number of special purpose lens designs that work well for computer glasses. Because these lenses are prescribed specifically for computer use, they are unsuitable for driving or general purpose wear. The simplest computer glasses have single vision lenses with a modified lens power prescribed to give the most comfortable vision at the user’s computer screen. These lenses relax the amount of focusing the eyes have to do to keep images on the computer screen clear and provide the largest field of view, reducing the need for head tilting and other unnatural posture changes during computer work. For older computer users, a specially designed progressive lens for computer use is sometimes a better option. Progressive lenses for computer use have a larger intermediate zone than regular progressive lenses for a wider, more comfortable view of the computer screen. Another option for presbyopic computer users is a lined trifocal, with a larger intermediate zone than regular trifocals. Still another possibility is an occupational bifocal, with the top part of the lens for intermediate vision (computer screen) and the bottom portion for near vision (reading). Your eyecare professional can help you decide which lens design will best suit your needs. Lens coatings and treatments Anti-reflective (AR) coating can make your computer glasses even more comfortable. This coating reduces glare caused by reflections of overhead fluorescent lighting that can occur in uncoated eyeglass lenses. Also, because many office environments are too bright for optimum visual comfort, a light tint is often a good idea as well. Special tints are available that selectively block different wavelengths of indoor lighting for greater comfort. For more information on presbyo pia and
Article ©2008 Access Media Group LLC. All rights reserved. Reproduction other than for one-time personal use is strictly prohibited
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Computer Eyestrain: 10 Steps for Relief
With so many people using computers at work, eyestrain has become one of the leading office-related health complaints.
Experts estimate 50% to 90% of computer users experience some degree of eyestrain or other symptoms of computer vision syndrome (CVS) during their work day. Studies showeyestrain and CVS often cause fatigue, decreased productivity and more work errors.
So what can you do about it? Here are steps you (and your employer) can take to reduce computer eye strain and the other common symptoms of computer vision syndrome (CVS):
1. Get a computer eye exam.
This is the most important thing you can do to prevent computer vision problems. According to the National Institute of Occupational Safety and Health (NIOSH), computer users should have an eye exam before they start working on a computer and once yearly thereafter. Be sure to tell your eye doctor how often you use a computer at work and at home.
2. Use proper lighting.
Computer eyestrain is often caused by excessively bright ambient lighting — either from outdoor sunlight coming in through a window or from harsh interior lighting. For the most comfortable computer use, ambient lighting should be about half as bright as that found in most offices.
If possible, reduce the brightness of interior lighting by using fewer fluorescent tubes in overhead light fixtures or use lower intensity bulbs. If possible, position your monitor so that windows are to the side of it, instead of in front or back. Adjust window blinds to reduce the amount of sunlight entering your workstation.
3. Minimize glare.
Glare on walls and finished surfaces as well as reflections on the computer screen can also cause computer eyestrain. You may want to install an anti-glare screen on your monitor and, if possible, paint bright white walls a darker color with a matte finish.
Again, cover the windows. When outside light cannot be reduced, consider using a computer hood.
If you wear glasses, have an anti-reflective (AR) coating applied to your lenses. AR coating reduces glare by minimizing the amount of light reflecting off the front and back surfaces of your eyeglass lenses.
4. Upgrade your display.
If you’ve not already done so, replace your old tube-style monitor (called a cathode ray tube or CRT) with a flat-panel liquid crystal display (LCD), like those on laptop computers.
LCD screens are easier on the eyes and usually have an anti-reflective surface. Old-fashioned CRT screens can cause a “flicker” of images on the screen. Even if this flicker is imperceptible, it can still contribute to eyestrain and fatigue during computer work.
If you still use a CRT, you can decrease eyestrain from flicker by increasing the refresh rate of your screen to 75 hertz (Hz) or higher. You can access this setting in the Control Panel of your computer.
When choosing a new flat panel display, select a screen with the highest resolution possible. Resolution is related to the “dot pitch” of the display. Generally, displays with a lower dot pitch have sharper images. Choose a display with a dot pitch of .28 mm or smaller.
Finally, choose a relatively large display. For a desktop computer, select a display that has a diagonal screen size of at least 19 inches.
5. Adjust the brightness and contrast of your computer screen.
For more comfortable viewing, adjust the display settings on your computer so the brightness of the screen is about the same as your work environment.
As a test, try looking at the white background of this web page. If it looks like a light source, it’s too bright. If it seems dull and gray, it may be too dark.
Also, adjust your screen settings to make sure the contrast between the screen background and the on-screen characters is high. And make sure that the text size and color are optimized for the most comfort. Usually, black text on a white background is the best color combination. But other high-contrast, dark-on-light combinations may also be acceptable.
6. Blink more often.
Blinking is very important — it rewets your eyes to keep them moist, comfortable and clear.
Studies show that, during computer use, most people blink only about 20% as frequently as they normally do. This greatly increases the risk for dry eyes, blurred vision, eye irritation and fatigue.
To keep your eyes comfortable and seeing well during computer use, try this exercise: Every 20 minutes, blink 10 times by closing your eyes as if falling asleep (very slowly). This will help rewet your eyes.
Also, keep a bottle of artificial tears at your workplace and use them to moisten your eyes often during prolonged computer use. Ask your eye doctor to recommend the best brands for your needs.
7. Exercise your eyes.
Another cause of computer eyestrain is focusing fatigue. Research shows that it’s harder for our eyes to maintain focus on computer-generated images than on printed images in a book or magazine.
To reduce your risk of focusing fatigue during computer use, look away from your screen or monitor every 20 minutes and gaze at a distant object across the room. Looking far away relaxes the focusing muscles inside your e
yes, reducing focusing fatigue.
Another exercise is to look far away at an object for 10-15 seconds, then gaze at something up close for 10-15 second–then look back at the distant object again. Do this 10 times. This exercise reduces the risk of your eyes’ focusing system from “locking up” (a condition called accommodative spasm) during prolonged computer work.
8. Take frequent breaks.
Take frequent, short breaks from your computer work throughout the day. Stand up, walk away from your work station and stretch your arms, legs, back, neck and shoulders. These activities will reduce your risk for computer vision syndrome and neck, back and shoulder pain.
Many workers take only two 15-minute breaks from their computer during their work day. According to a recent NIOSH study, computer workers experienced significantly less discomfort and eyestrain if they took four additional 5-minute “mini-breaks” during the day.
Interestingly, these supplementary breaks did not reduce productivity. Data entry speed was significantly faster as a result of the extra breaks, so work output was maintained even though the workers had 20 extra minutes of break time each day.
9. Modify your workstation.
Looking back and forth between a printed page and your computer screen (as during data entry tasks), can also cause eyestrain. To improve comfort during these tasks, place the print material on a copy stand adjacent to your screen or monitor. If necessary, use a desk lamp to illuminate the print material–but make sure it doesn’t shine into your eyes or onto the computer screen.
Improper posture during computer work also contributes to computer vision syndrome. Adjust your workstation and chair to a comfortable height so your feet are flat on the floor in front of you.
Adjust your chair and computer so your screen is approximately 20 to 24 inches from your eyes and slightly below eye level so you can view it comfortably with your head and neck in a natural position.
10. Consider computer eyewear.
For the greatest comfort at your computer, you may benefit from having a customized eyeglasses prescription for your computer work. This is especially true if you normally wear contact lenses, that can become dry and uncomfortable during sustained computer work.
Computer glasses are also a good choice if you normally wear eyeglasses with bifocal or progressive lenses. Though these lenses provide excellent vision for most tasks, they don’t provide an adequate viewing zone for prolonged computer work.
Your eye doctor can prescribe specially-designed computer eyewear to give you the best possible vision at your computer screen. Keep in mind that computer glasses are a specific type of eyewear and typically should not be worn when driving.
For more information on computer glasses and computer vision, visit All About Vision®.
Article ©2008 Access Media Group LLC. All rights reserved. Reproduction other than for one-time personal use is strictly prohibited.
Children and Computer Vision Syndrome
Computer use has become a routine part of kids’ lives. Surveys show the average American child spends one to three hours daily on a computer while surfing the Internet, doing homework, talking online with friends and playing video games. About 90% of school-aged children in the U.S. have access to a computer at home or in school. And kids are starting to use computers at a younger age. Among college students who were interviewed, 20% said they began using a computer before they were 9 years old. A connection between computer use and myopia? So how is all this computer use at a young age affecting kids’ eyes? Many eye doctors who specialize in children’s vision say sustained computer use puts kids at higher risk for childhood myopia (nearsightedness). They point out that, though myopia affects approximately 25% of the U.S. population, nearly 50% of adult computer users with a college education are nearsighted. Computer use, especially among youngsters whose eyes are still changing, may be the reason for this disparity. Research seems to support this theory. A study of 253 children between the ages of 6 and 10 at the University of California at Berkeley School of Optometry found a strong correlation between the amount of time young children spend on the computer and their development of nearsightedness. Why computers can be hard on kids’ eyes Computer use stresses the eyes more than reading a book or magazine because it’s harder to maintain focus on computer-generated images than on printed images. This is especially true for young children, whose visual system is not fully developed. According to the American Optometric Association, children may be especially vulnerable to computer-related vision problems because:
Tips for preventing Computer Vision Syndrome in children
To prevent your child from developing eyestrain and other CVS symptoms (including increasing myopia), follow these tips:
- Before they start school, make sure your kids have a comprehensive eye exam–including an assessment of their near-point (computer and reading) vision skills.
- Make sure your child’s computer workstation is arranged to suit body size. For children, the recommended distance between the monitor and the eye is 18 to 28 inches to avoid risk of eyestrain with closer viewing. Also, the screen should be a few inches below the child’s eyes. The chair should be adjusted so arms are parallel with the desk surface and feet rest comfortably on the floor. These adjustments help avoid posture problems and strained muscles.
- Be aware of the signs and symptoms of vision problems, such as eye redness, frequent rubbing of the eyes, head turns and other unusual postures or complaints of blurriness or eye fatigue. Avoidance of the computer or school work may also indicate a vision problem.
If you suspect your child may be developing a vision problem related to computer use, be sure to mention this when you make an appointment for an eye exam. Your doctor may want to set aside extra time to perform tests specifically designed to detect computer vision problems.
For more information on myopia and computer vision syndrome, visit All About Vision®.
Article ©2008 Access Media Group LLC. All rights reserved. Reproduction other than for one-time personal use is strictly prohibited.
