Computer Vision Syndrome


What Is CVS?

Computer vision syndrome (CVS) represents a group of visual and extraocular symptoms associated with sustained use of visual display terminals. Approximately three-fourths of people who work hard on the computer are affected by these symptoms. The number of people suffering from CVS seems to be rising with the increasing use of computers at workplaces and even at home.

CVS Symptoms

The most important symptoms of CVS include eye fatigue, dryness, burning, tearing and blurred vision. CVS may also cause pain in the neck and shoulders.

Human eyes see printed letters better than letters of digital texts displayed on computer screens. Because printed letters have more contrast with white paper and their edges are sharper, while computer screens are not the same as white paper, and the edges of digital letters are not as clearly as printed letters. Letters of digital texts on monitors have a high contrast at center, which gradually gets pale and disappears after turning into a pale gray. Therefore, the edges of letters on a monitor do not have the resolution of the printed letters.

One of the main reasons of dryness and burning eyes in most computer users is their low blink rate, so that people tend to blink less, about one-fifth of the normal blinking rate when working on a computer. When you concentrate on a computer screen and focus on a subject, it makes your eyelids remain open for a long time, which causes tears evaporate too quickly.

10 Recommendations for Reducing CVS Symptoms

1. Try to blink voluntarily. This causes tears lubricate the surface of your eyes and prevent from eye dryness. If you have severe eye dryness, you can use artificial tear drops.

2. The center of the screen should be located about 10 to 20 centimeters below your eyes level. In this position your eyelids are semi-open and your eyes are less exposed to the air. It also reduces the fatigue of the neck and shoulders. Your monitor should be placed at an appropriate height. Then adjust the height of your chair according to your desk, so that your arm during working with keyboard is located parallel to the ground.

3. Position your monitor so that the light of windows or the room's lamp is not reflected on it. When you use a computer, eliminate exterior light by closing drapes, shades or blinds; your ambient lighting should be about half as bright as that typically found in most offices. If you use a desk lamp on your desk, place it so that its light is not reflected on your computer screen or eyes. You can also use monitor filters. The light is emitted from computer screens reduces contrast and leads to eye strain. This will be more severe, especially when the background of the screen is dark.

4. Give your eyes a break. Try to take your eyes every 5 to 10 minutes from the monitor and look into the distance for 5-10 seconds. This make your eye muscles relax. It also gives you time to blink to keep your eyes moist.

5. If you have to look at your monitor alternatively (especially for typists), your eye may be tired because each time you should change your visual accommodation. To avoid this, try to position your printed materials at least at the same distance and level from your monitor. You can use a copyholder for this.

6. The distance between your monitor and eyes should be 50 to 60 centimeters.

7. Adjust the brightness and contrast of your monitor. It should be approximately the same as the brightness of your surrounding. As a test, look 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. In general, the brightness should be so much that your eyes feel comfortable. The contrast of the monitor should be maximized so that the edges of the letters will have the highest contrast with the text.

8. Adjust your computer other display setting. The quality of displaying images on the monitor depends on three factors: Resolution, Refresh Rate, and Dote Pitch.

Refresh Rate represents the frequency of image repetition on the monitor. The low frequency can be tedious for the eye and very low frequencies cause the image to jump. The best refresh rate is about 70 Hz or more. Resolution refers to the image pixel density on the monitor. The more pixels are, the more detailed of the image can be seen. In general, the higher the resolution is, the better the image is. Refresh rate should also be considered. Sometimes high resolution has a low refresh rate so you should choose a situation that both have the largest number.

Dot Pitch is effective on sharpness of the image, and the smaller the number is, the sharper the image is. Most Dot Pitch monitors range from 0.25 to 0.28 mm. 28 mm or less is the desired number. You can set Refresh Rate and Resolution in Windows Display Properties, but Dot Pitch can not be adjusted.

9. If you still have symptoms of CVS in spite of the advice given, you can wear special glasses because sometimes the problem is related to middle vision. We usually use middle vision less, because we often see distance or close objects. But the computer monitor is exactly located at the distance from your eyes which is related to middle vision. If you are wearing glasses, your glasses are unlikely to be suitable for work with the computer because it does not correct the middle vision. An ophthalmologist or optometrist can prescribe for you appropriate computer glasses.

10. When working with a computer, try to hold your neck straight and pull your shoulders backwards. Bending over for long periods of time when you work with computer can cause neck and shoulder pain. If the back of your seat is adjustable, adjust it to fit perfectly behind you. Also adjust the height of your chair so that your feet are flat on the floor, with your knees at a 90 ° angle. Keyboard and Mouse should be located below your elbow and close to your hands.

Last Point:

If you have still eye problems when working on the computer, you should see an ophthalmologist as soon as possible.