COMPUTER, VISION AND RSI

Visual discomfort is one of the most frequently cited complaints of computer workers. Specialists like James Sheedy at the VDT Eye Clinic at the University of Berkeley School of optometry believe that computer users can develop repetitive strain injury of the eye, and the governmental agency NIOSH estimates that over 60 million Americans suffer from computer eyestrain.

Eyestrain and headaches are the most common complaints associated with vision. Other problems include double or blurred vision, burning and dry sensations, ocular fatigue, loss of focus, and other visual disturbances. Neck and back pain can also be related to viewing the computer keyboard and/or screen. Although no permanent eye damage has been attributed to computer use, comfortable vision is important to maintain.

COMPUTER RELATED EYE PROBLEMS

Bifocals:

Bifocals are designed for reading at an approximate distance of 16 inches. The typical computer monitor is positioned 18 to 30 inches away from the user. Bifocals are angled downward at a 25 degree angle for comfortable reading; the optimal viewing angle for the computer screen has generally been thought to be 10 to 15 degrees below horizontal. As a result, bifocal users must tilt their necks and heads in order to see the screen. Bifocal wearers should measure the distance from their eye to the computer monitor and inform their eye doctor of this information for proper adjustment of bifocals for computer use. It is also a good idea to lower the monitor so that the neck can remain in a neutral position while looking out of the glasses.

One other option would be to get a pair of glasses that are used solely for the computer.

Contact Lenses:

Individuals who wear contact lenses blink less than people who have normal vision or wear glasses. Contact wearers must be educated to blink often and use artificial tears to reduce eye irritation. NOTE: Do not use vasoconstrictors to reduce redness and irritation in the place of artificial tears.

Differences in Computer versus Printed Material:

Printed material is characterized by smooth, dense, black lines with edges that are well defined. Eyes focus to printed material differently than characters on the computer screen, because the characters on the computer screen fade out around the edges. The characters are the brightest in the middle and then fade out, so the eyes have difficulty focusing on them. Instead the eyes focus to a further point called the RPA or the resting point of accommodation and then the eye muscles must flex to get the images on the screen focused. The eyes end up being overworked and this can result in eyestrain.

Acuity and Focusing Problems:

Difficulties in the eye focusing mechanism and eye alignment can result in eyestrain, neck pain and headaches during computer work. To avoid problems, have your vision checked by an eye doctor aware of problems that can interfere with computer vision.

VISION TIPS

  • Rest your eyes for at least 20 seconds every 30 minutes at a minimum.
  • Change the distance of your focusing during rest periods. Look out the window at a far object if possible, or focus on something across the room.
  • Keep your screen clean with proper contrast.
  • Reduce glare on your screen by eliminating or reducing overhead, direct lighting or direct glare for windows, etc.
  • Try to keep the lighting levels in your office as even as possible. Eye strain is increased when there are contrasting light levels in your work area.
  • Use glare guard on your computer screen to reduce glare.

VISION AND POSTURE

The location of the visual target plays a major role in determining sitting posture. Visual requirements result in the user positioning the body so that the face is parallel to the viewing surface. This principle should be remembered when determining placement of a monitor. Unless you wear bifocals, the top of the monitor should come to approximately your mid forehead when it is adjusted to the proper height. Most monitors can be tilted up or down which can help in setting the height as well. Be sure to test for excessive glare when tilting the monitor. If you can see your own image in the monitor screen before it is turned on, reflections and indirect glare from the screen will strain your eyes when working at the VDT.

Most experts are now saying that the viewing distance from your eye to the monitor should be 20 to 30 inches. If you wear bifocals or have vision problems that require you to move it closer or further away, it is important that you do this.

Document holders are generally placed to the side of or in front of the monitor (when placed in front it is angled up between the keyboard and the monitor). When placing the document holder to the side of the monitor, the dominant eye should be considered. Favoring the dominant eye with the most frequently used visual targets may require less eye, head, neck and body movement to view these targets. This is due to the fact that the center of the visual field is closer to the dominant eye than the non-dominant eye. A left-eye-dominant person should position frequently viewed documents to the left of the monitor. If the monitor is the most frequently viewed item, then it should be positioned to the side favoring the dominant eye.

To determine eye dominance, do the following while sitting in front of your computer screen:

1. Holding your arms straight out in front of you, make 2 circles, one with each of your hands. Position your hands so that you can see through both circles with one hand in front of the other. Focus on a distant object with both eyes open. Wear glasses if you normally use them to work at your computer.

2. Continuing to hold your hands in position, close one eye and then the other. The eye allowing you to see the distant object is your dominant eye.

Information is condensed from the following:

Repetitive Strain Injury by Pascarelli and Quilter.

Vision Comfort at VDT’s by Stewart Leavitt (800-966-5511)

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