User:Rewood/Eyestrain and VDTs
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Eyestrain is another ergonomic problem frequently associated with the use of computers and Video Display Terminals (VDTs).
Symptoms of eyestrain may be:
- Sore, tired, itchy, dry, or burning eyes
- Difficulty focusing between the VDT and source documents
- Blurred or double vision
- Color fringes / after images
- Increased sensitivity to light
These symptoms may be caused by:
- Improper lighting: If the light in the work area is too bright or too dim, the human eye has to work extra hard to compensate for these harsh environmental factors. People may not even be aware that their eyes are under duress, but over time they may develop symptoms of eyestrain.
- Solution: Use indirect, ambient lighting and an adjustable light source at the desk, where extra illumination is required.
- Glare: Glare can be caused by sources of light such as windows, lamps, or overhead lighting. Look at your monitor screen to see if there are any bright blotches of light. While you may not be conscious of this irritation, it can cause eyestrain over the course of a long day. Glare can also be caused by too much contrast between the screen background and the displayed text.
- Solution: Adjust your monitor so that it is not reflecting the light source. Tilt the monitor down so that it doesn't reflect overhead lights, or move it perpendicular to windows. Close shades or blinds if the computer cannot be moved. Move lamps so that they are not reflected directly in the monitor. Use glare screens.
- Eyewear: Many computer users wear bifocals or trifocal lenses fitted for reading print and distance viewing. Sometimes these prescriptions may not be adequate for computer work.
- Solution: If you wear glasses of any sort and frequently experience headaches while working at a computer, you should probably check with your eye doctor to make sure you are wearing the correct prescription for such work.
- Viewing angle and distance: If your monitor is too far away, you will have to strain to read the print. Likewise, if it is too close, you may also strain your eyes. If the monitor is too high, you will have to angle your neck to look up at it, which could cause your neck to be sore, and may contribute to headaches. Also, when you are continually looking up, you may not fully close your eyes when you blink, and this can cause your eyes to dry out.
- Solution: Generally speaking, the recommended distance for the monitor is between 18-30 inches from the user, with the first line of text just slightly below eye level. You want the keyboard directly in front of the monitor. If the keyboard/monitor is off to one side, the distance to the monitor may be slightly different for each eye, causing them to focus separately.
- Uninterrupted focus on the screen: When people concentrate, they blink less often. Sometimes they concentrate so hard that they blink only once per minute, instead of the normal once every five seconds. This, too, will cause the eyes to dry out and become irritated.
- Solution: Take micro-breaks! Frequently look up from your monitor and focus on an object several feet away. Make a conscious effort to blink.
- VDT and document holder location: If the document holder is below the VDT or off to the side, each time your eyes look from one source to the other, your pupils have to adjust. If you have to do this for long periods of time, it can cause headaches and eyestrain.
- Solution: Place document holder at the same level, angle, and distance as the screen to avoid having to shift eye focus.
- Dust on screen: A buildup of dust on the screen can make it hard to distinguish characters. This may also contribute to glare and reflection problems.
- Solution: Dust off your monitor every day.