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 Computer Vision Syndrome (CVS)

How is reading a monitor different from reading a printed page?
What are the signs of CVS?
What steps can you take to minimize CVS?
Where should the monitor be located?
How should the monitor be lighted?
How should your body be positioned in front of a computer?
How can you care for your eyes when using a computer?

According to the American Optometric Association (AOA), Computer Vision Syndrome (CVS) is "the complex of eye and vision problems related to near work which are experienced during, or related to, computer use." For the computer user, that translates to red, itchy, watery, irritated eyes, along with eye fatigue, difficulty focusing, and a variety of other problems. The AOA says that about 14 percent of patients who schedule eye exams do so because of CVS.

In the United States, it's estimated that about two-thirds of those who use a computer -- nearly 60 million people -- suffer from related eye or vision problems. The National Institute of Occupational Safety and Health reports that 88 percent of people who work at computers for more than three hours per day, suffer from eyestrain.

At greatest risk for CVS are those who spend two or more continuous hours at the computer every day. Each year, this includes a larger proportion of the workforce, and it includes most students, who now routinely use the computer for both work and play.

Currently no clinical evidence suggests that computer use results in permanent vision problems. However, that fact is little comfort to those who experience eye discomfort because their occupations or schoolwork keep them at computers several hours every day. Eye doctors are becoming concerned that the 21st century could see an epidemic of computer-related eye problems unless businesses, schools, and computer manufacturers devote substantial resources to solving the problem.

How is reading a monitor different from reading a printed page?

Reading a computer screen is hard on your eyes because of the way the characters are formed on the monitor. The video display is made up of pixels, or tiny dots, rather than solid images as on a printed page. Because your eyes cannot "lock" focus on these dots, your eyes must continually focus and refocus to keep the image sharp. This refocusing results in stress to your eye muscles. In addition, your eyes blink less frequently when you are using a computer, causing the eye surface to dry out and become irritated. The irritation makes focusing even more difficult, which can lead to headaches and neck pain.

Many of the problems related to CVS are ergonomic, relating to the body's relationship to its work environment. For instance, when a monitor is positioned too high, you must open your eyes wide to look up and view it. Therefore, your eyelids are retracted farther than normal and more tears evaporate. On the other hand, if the monitor is low and you are looking down to view it, your eyes will remain moist, reducing the chance of dry eye. According to some studies, eyes produce more tears than normal when looking down.

Computer Vision Syndrome can be even worse for people who have refractive disorders, binocular vision, accommodative (focusing) disorders, or dry eye.

Children who use computers may be even more susceptible to CVS than adults. Children often keep performing enjoyable tasks, such as computer games, with great concentration for hours with few breaks. This type of prolonged activity without significant breaks can cause eye focusing problems and eye irritation.

What are the signs of CVS?

Employees suffering from CVS experience headaches, eyestrain, itchy eyes, blurred vision, fatigue, and tense muscles. Extreme CVS can even cause nausea, poor nutrition and loss of appetite, migraines, and cluster headaches. In addition to a strain on the muscles that control eye movement and focusing, prolonged computer use can also cause a tightening of facial muscles around the cheeks, temples, and nose. This facial tightening leads to reduced blood circulation, compounding the effects of eye fatigue.

Parents should be aware of how long their child spends on the computer at one time. Children often do not mention such symptoms as blurred vision caused by nearsightedness, farsightedness, or astigmatism because they think everyone sees the way they do. Uncorrected farsightedness can cause eyestrain at the computer because the eyes must work hard at focusing on a near object for an extended period of time. Every child over the age of 4 should have a comprehensive eye exam to be sure that vision problems are diagnosed and corrected. This is particularly important because children now spend so much time in front of a computer.

What steps can you take to minimize CVS?

The most important factors in preventing and treating CVS have to do with the ergonomic environment, which is the body's position relative to the computer and the external environment. This includes lighting conditions, chair comfort, location of reference materials (perhaps using document holders), and the position of the monitor, keyboard, and mouse.

Where should the monitor be located?

Most people find it more comfortable to view a monitor when the eyes are looking downward, yet many monitors are placed at or above eye level. Optimally, the computer monitor should be 20 to 30 degrees below eye level (about 5 or 6 inches) as measured from the center for the screen, and 20 to 28 inches from the eyes.

Reference materials being used at the computer should be above the keyboard and below the monitor. If this is not possible, use a document holder beside the monitor. When you are using documents at the computer, the goal is to position them so you do not need to move your head to look from the document to the screen.

How should the monitor be lighted?

Because glare on the computer screen, particularly from overhead lighting or windows, is another cause of eyestrain, position the monitor to avoid these problems. Use blinds or drapes at windows, and replace the light bulbs in desk lamps with bulbs of lower wattage. If there is no way to minimize glare from these light sources, consider buying a screen glare filter from a computer store. Through polarization, these filters decrease the amount of light reflected from the screen.

Overhead fluorescent lighting is the most uncomfortable type of lighting for many computer users because it seems to "flicker" in the peripheral vision. For some reason, this problem is worse with fair skinned individuals. If possible, turn off these lights, or use special parabolic louvers, which direct light straight down. The best light for computer operations is indirect or reflected light, such as that provided by an inverted halogen lamp.

How should your body be positioned in front of a computer?

Most computer users spend hours in the same position. Therefore, you should pay attention to comfort and position of your body, especially your arms, hands, and wrists. Chairs should be comfortably padded and conform to the body. If your chair cannot be adjusted, get a chiropractic pad, which contours to your lower back. Chair height should be adjusted so your feet rest flat on the floor. If your chair has arms, they should be adjusted to provide arm support while you are typing. When your shoulders have to support the weight of your arms for long periods of time, your shoulders, back, and neck can ache.

Wrist discomfort is a common complaint of those who use computers for an extended period of time. Use soft wrist pads in front of the keyboard to raise your wrists just above keyboard level. Your wrists should never rest on the keyboard when you are typing. Only your fingers should move when you are typing, as your wrists stay stationary. The mouse should be positioned near the keyboard and at about the same level.

The quality of your monitor and the size and color of the characters are often not given enough consideration by those who spend long periods of time at a computer. Choose a color monitor that has the highest resolution possible, usually less than 0.28 mm. Because computer text letters are electronically generated and have less contrast than hard copy text, they should be about three times bigger than the type on a printed page. Computer text should be about 3 mm to 3.5 mm in height with spaces between the lines of approximately 1 mm. It is usually easiest to read black letters on a white background, called negative contrast letters. However, when there is a large amount of "flicker" in the screen that can't be fixed by adjusting the screen brightness, it may be helpful to read white or yellow characters on a dark background.

How should you care for your eyes when using a computer?

To prevent CVS, try to rest your eyes when using the computer. Rest your eyes for 15 minutes after two hours of continuous computer use. Also, for every 20 minutes of computer time, look into the distance for 20 seconds -- the "20/20" rule.

Special eye drops are available to help relax tired eyes and supplement the lack of natural tear flow during computer use, but the best treatment is to prevent the problems from occurring. To minimize your chances of getting dry eye when using a computer, make an effort to blink frequently. Blinking keeps the front surface of your eye lubricated. Also, closing your eyes and rolling them behind your closed eyelids can help keep your eyes moist. If there are air vents in the room, try to prevent the draft from passing between your eyes and the computer monitor.

If you wear eyeglasses, consider using eyeglass lenses specially designed for computer users to help reduce CVS. Tinted lenses can sometimes help with glare and flicker. Gray or brown graded tints (which gradually get darker from top to bottom) seem to be best because they do not change color perception.

If you wear bifocals, your bifocal lenses can be a problem when using a computer, because you must tilt your head back to read the monitor through the near-vision portion of your lenses at the bottom of your glasses. In this case, consider purchasing special eyeglasses that contain only near and/or mid-vision correction. They allow your eyes to focus more easily.

If you suffer from work-related eyestrain, ask your employer for a complete workstation analysis and for improvements to make your workstation as ergonomically designed as possible. Employers should position monitors to avoid glare, conduct safety seminars to teach employees to exercise their eyes and give their eyes frequent breaks during long periods of work, offer special computer glasses, and ensure the proper height of seating in relation to computer monitor height.

Children may not be aware of glare on the computer screen or an uncomfortable seating condition. Therefore, if you are the parent of a computer-user child, make sure your child is in a comfortable position at the computer, that problems such as screen glare are eliminated, and that your child takes frequent breaks, using the computer for short periods of time.


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