Computer Vision Syndrome (CVS)
 
A common problem - On average, more than 50% of the work force now uses a computer on the job - It's estimated that over 60 million working Americans suffer from computer eyestrain and there are a million new cases each year. Their condition is called Computer Vision Syndrome or "CVS".  If you spend more than two hours each day in front
of a computer screen, you are likely to experience at least some of the symptoms of Computer Vision Syndrome.

CVS is characterized by dry, red, itchy, or watery eyes; fatigue, heaviness of the eyelids or forehead; and difficulty focusing. These symptoms can cause headaches, backaches, and muscle spasms. Many aspects of CVS meet the same criteria used to define repetitive stress injuries.


What causes CVS? - Computer Vision Syndrome is related to the unique aspects of the task; working at a computer is more visually demanding than doing other standard office work. Our eyes and brain react differently to characters displayed on a computer screen than they do to characters printed on paper. Computer images are generally less distinct than printed characters, may have perceptible flicker, and usually have less contrast between characters and the background on which they appear. Flat panel (LCD) displays do have some advantages compared to cathode ray tube (CRT) displays. In particular, LCD displays do not flicker and the contrast is usually greater than it is with CRTs.


Using the wrong "tool" for the job - Glasses prescribed for "every-day" visual needs for most tasks usually do not properly correct the vision for the VDT work station. The most common method for prescribing and designing bifocals is to prescribe a lens power which will provide clear vision at 40 cm (16 inches) - this is the standard testing distance used by eye doctors. The VDT screen is usually further away (20-28 inches) than the usual testing distance of 16 inches.

Also, a typical bifocal lens placement and downward viewing angle of 25 degrees is not well suited for viewing a VDT screen (normally only 10-20 degrees downward.) A VDT user who tries to wear their every-day bifocal correction at the VDT will either not see the VDT clearly or will need to assume an awkward posture. Most commonly, they will need to lean closer to the screen and tilt their head backwards, leading to neck and back strain. Trifocals and standard progressive lenses are somewhat better but they have a fairly small intermediate area, which is often not large enough for comfortable computer work.

Note: If you work frequently on a computer, make sure you tell your eye doctor during your eye examination. Before your exam, have someone at work measure how far it is from your eye to the keyboard and from your eye to the screen. Take the measurements with you to your eye exam and share them with your doctor.


A word about "laptop" computers - While they can be very convenient, due to their portability, "laptop" computers are not a good choice for bifocal wearers who need to work on the computer for extended periods. Since the keyboard and the screen cannot be separated, it's not possible to have BOTH the screen and keyboard optimally located. If you require bifocals and must use a laptop, using a separate monitor when working for extended periods is highly recommended.
 
Ergonomics - Making it easier on yourself

 
   
1. Take a look at your monitor right now. Is it a reasonable distance from your eyes? It should be about 20 to 26 inches away. Is your document holder near it? Place your document holder as close to the screen as possible: constantly looking back and forth between them can tire out your eyes.

2. Position your computer so that any windows are to the side of the monitor, rather than in front or in back. Position any desk lamp so
it doesn't shine on the computer screen or into your eyes

 3. Make sure your monitor is neither too high nor too low. CVS expert Dr. James Sheedy of Ohio State University College of Optometry recommends that the center of the screen be 4 to 9 inches below your straight-ahead gaze. If you reposition your chair or monitor, keep in mind that your arms should be parallel to the floor when you type, and your feet should be flat on the floor.

4. Place a glare filter over your monitor screen.

5. Attach a glare-blocking hood to your monitor. Much as a jacket hood can
reduce the amount of sunlight that reaches your eyes from
the top and sides of your head, a monitor hood reduces the amount of light that can reach your screen.

Note: Filters are generally available from office supply stores but monitor hoods are less common. If your office supply store does not carry them, you can find one by looking online.

6. Take a break. Several times per hour, briefly look around at things that are at varying distances from your computer, like a clock on the wall, or something outside a window.

7. Finally, you might benefit from eye drops. Look for the ones marked "lubricating" or "lubricant," as other kinds can be addictive, even in over-the-counter strength. Avoid frequent use of any drops designed to whiten the eye.
 

Adjusting your monitor

Text Size and Color - Adjusting how your monitor displays text can provide welcome eyestrain relief. Ideally, your text size should be three times the smallest text size you can read from your normal viewing position. Black text on a white background is the best color combination for your eyes but other high-contrast, dark-on-light combinations are also acceptable, according to Dr. Sheedy.

To adjust the text size and color settings in a Windows operating system, use the
"Display Properties" dialog box, which is available from the Control Panel. Depending on which version of Windows you have, font size will either be on the "Settings" tab or the "Appearance" tab. Color choices are on the "Appearance" tab.

Brightness and Contrast - Most monitors allow you to adjust the brightness and contrast so that they're easy on your eyes. Brightness and contrast controls are usually buttons on the front of the monitor. You adjust screen brightness to match the room brightness. After you're finished with the brightness, adjust the contrast to the highest amount you are comfortable with (this should be a very high level of contrast).


In Conclusion

Specially-designed computer glasses and/or ergonomic adjustments should clear up your aches and pains. If you've tried all the options in this article and find that using the computer still bothers your eyes, it's a good idea to schedule an appointment with your eye doctor.

Sources:   Back to Top
1. American Optometric Association    
2. allaboutvision.com    
3. Bausch and Lomb    
4. James Sheedy, OD, PhD    
  
Vision & Health Newsletter courtesy of:
 		  
Dr. Philip Smith & Associates
1855 1st Ave #100
San Diego, CA 92101

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