Computers and Vision
Computers use, nowadays is a fact of life. Most of us use computers either for work, leisure or socially to communicate with friends and family. Many people who use a computer for extended periods of time will experience some degree of vision problems, eyestrain, general discomfort or fatigue. These problems are referred to as computer vision syndrome (CVS). CVS should not cause permanent damage to your eyes, but it can cause discomfort and loss of productivity.
What causes CVS?
Working at a computer requires a number of visual skills. When looking at the screen your eyes have to converge and meet at particular points, focus, move to another point and refocus continuously. This may sound an awful lot like the eye movement for reading, so why is it any different?
- The resolutions of most computer screen are lower than on printed paper. Resolution influences the shape and edge sharpness on a page. The lower the resolution makes it more difficult to maintain comfortable focus.
- Cathode-ray tube monitors cause images to flicker. Though most computer users are unaware of this flicker, it contributes to eyestrain. Fortunately, many are now being replaced by flat screen LCD displays that eliminate this problem.
- Also, in a cathode tube type monitor, 1000’s of pixels combine to form what you see on the screen. However, each pixel has a bright centre but fades out towards the edges. Researchers suggest that because of this, our eyes cannot stay properly focused and tend to drift in and out of focus. This leads to eye fatigue and other symptoms of CVS.
- Many computer monitors cause distracting reflections. This can also make focusing more difficult and can lead to eyestrain.
- Studies show people don’t blink frequently enough when using the computer. Most people normally blink 16 to 20 times per minute. However when using a computer your blinking rate can drop to 5 to 7 time per minute. This may not seem like a big deal, but, infrequent and incomplete blinking can cause eyes to become dry, red and irritated leading to eyestrain and blurred vision.
What are the symptoms of CVS?
Symptoms fall into three main categories as follows:
- Vision problems. These can include blurred vision, glare, flickering sensations, difficulty changing focus, double vision, and temporary changes in colour perception.
- Eye problems. These include a burning sensation, redness, soreness, stinging, dryness, excessive tearing, itchiness, eye fatigue, eyestrain, light sensitivity, and contact lens discomfort.
- General discomfort. These can include excessive fatigue, headaches, shoulder tension or pain, neck tension or pain, back pain, pain in arms or wrists, irritability, and drowsiness.
The importance of posture
Many people have poor posture when sitting at a computer. This can be due to physical setup of the area you work and because people tend to want to lean closer to the screen over time to see it. The longer you sit at a computer screen the more likely you are to experience headaches, backache, stiffness neck and shoulder discomfort and arm and wrist pain from poor posture or overuse of certain muscles.
How is computer vision syndrome treated?
The first step is to have a complete eye exam. Tell your optician that you are using a computer and explaining what kind of symptoms you are experiencing as well as whether you typically wear glasses or contact lenses when using a computer.
Most people who use the computer for long periods of time do benefit from wearing glasses specifically prescribed for computer use. These work by helping your eyes maintain proper focus on your computer screen with less fatigue.
If you don't currently wear glasses or you wear glasses with single vision lenses, you are likely to be recommended single vision lenses that provide added magnification for viewing your computer screen. These glasses are designed for computer work and other near tasks only. The lens power in this type of eyewear will make your computer screen clear and more comfortable to read for prolonged periods, but it will make objects that are farther away appear less clear.
Bifocals and varifocal eyewear are generally unsatisfactory for long periods of computer use. Bifocals require you to tilt your head back to view the computer screen, causing neck stiffness and eyestrain. Varifocal lenses are better for computer use but the portion of the lens that contains the proper power for viewing a computer screen is typically too small, requiring frequent head movements to see the screen clearly. For prolonged use, it is worth considering buying a dedicated pair of single vision eyewear that you can then keep near your computer and wear when you plan to work at the computer for prolonged periods. All lenses worn for computer use should include an anti-reflective (AR) coating. This keeps light from reflecting off the lens surfaces, thereby preventing an additional source of glare.
How can I avoid CVS without buying glasses?
The following steps will help to reduce the effects of CVS.
1. Optimize your work station.
- Check your screen for reflections. Adjust lighting or window shades to help or rotate your screen to eliminate reflections. You can also consider buying an anti-reflective screen filter if reflections remain a problem.
- Most office environments have lighting that is too bright for comfortable computer use so if possible try to change this by reducing the light and utilising more indirect light.
- An improper screen location can cause poor posture. The ideal level is to have your screen about 24 inches from your eyes and about 6 inches below eye level.
- Tilting the screen so the top and bottom are the same distance from your eyes also helps. Ideally, the screen should be directly in front of you.
- It is best to keep your reference material as close to the screen as possible so there is less strain on your eyes. If possible use a document holder.
- And last but not least, a good chair is important. Sit with your back against the chair and your feet flat on the floor.
2. Check your hardware
- Adjust the contrast and brightness of your screen for greatest comfort. The brightness should be generally equal to the background brightness of the room. Also go for maximum screen resolution.
- Check the refresh rate of your monitor. Low refresh rates can cause flicker that is barely perceptible yet bothersome to the eyes. A refresh rate of at least 70 Hz is recommended.
- If you often work with spreadsheets, graphic designs or long documents it’s best to work on a 17inch or larger monitor, which is something to consider when next buying a computer monitor.
3. Take frequent breaks
- This is a quick, cheap and easy way of avoiding CVS. Closing your eyes or looking somewhere across the room for several seconds to rest your eyes is good. It is best to do this every 15 to 20 minutes. Some eye care professional call this the 20-20-20 rule: EVERY 20 minutes, take a 20 second break to look at objects at least 20 feet away. But going to the coffee machine is just as effective!
4. Blink often
- Do this whenever you feel your eyes are uncomfortable or lacking moisture. If your eyes still feel dry, use artificial tears or contact lens rewetting drops as often as necessary.
5. Get up and stretch
- Every 20 to 30 minutes get up and stretch as this relieves muscle tension and increases blood flow.
- BE AWARE OF YOUR POSTURE. Make adjustments to avoid sitting in a cramp position. Sit up straight with your back against the chair.