Saturday, August 31, 2013

Computers and the Eye-Bane, Boon, or Much Ado About Nothing?

Eye and visual problems are among the most commonly reported problems among computer workers, affecting up to 70% of such a population in some studies. The term Computer Vision Syndrome (CVS) refers to a range of eye and vision problems related to near work during computer use. It is not a specific disease, but rather, a range of symptoms related to visual demands exceeding the ability of a person to comfortably perform the task. Although associated with discomfort, there is generally no permanent harm to the eyes or vision.

Things that patients feel with computer use for prolonged periods include
1) non-specific eye discomfort (often called eye-strain)
2) transient blurred distance vision
3) transient blurred near vision
4) dry or irritated eyes
5) headache, and even
6) temporary double vision.

Why is there a problem with computer work when there may be no problems reading other things?
Working at a computer requires frequent eye movements, continuous eye focusing and alignment which involve repetitious muscular activity. For example, frequent eye movements from paper documents to the computer screen and back again occur. Viewing distances and angles for computer work are often different from those commonly used for reading and other tasks, with computer work often occurring at a distance slightly greater than the normal reading distance.

Aspects of the computer display such as resolution, contrast and glare also affect visual comfort. Often the letters on a video display screen are not as sharp as those on a printed page. The presence of reflections from the screen may also make viewing more difficult.

What factors may make the problem worse?
Uncorrected long or short-sightedness, astigmatism and ‘old-sight’ can make working at the computer more difficult. ‘Old sight’ or presbyopia refers to the natural loss of focusing ability (accommodation) with age that tends to become manifest at about 40 years of age. Some of these problems may not result in symptoms under less demanding conditions and some patients are not even aware of their presence. Patients experiencing problems should have a comprehensive eye test looking at the refractive power of their eyes.

Other possible conditions include undetected latent squints and dry eye. The prolonged concentration associated with computer work often results in a reduced blink rate, which causes dry eye because of increased evaporation of tears.

Children and computers
Today, use of computers by children is increasingly common both for education and play. Although children are more adaptable than adults in many ways, they are not as self aware and may ignore problems otherwise noticed by adults. For example, children may play an enjoyable game for hours until exhaustion. As a result of prolonged eye effort, many of the problems seen in adults may eventually be seen in children as well such as focusing problems and even dry eyes. Of concern also is the possibility of prolonged near work contributing to the progression of short-sightedness in children.

Children are also smaller than adults, and many computer work stations may not fit them well. Awkward postures may result in arm, neck or back discomfort.

When children use the computer, parents may want to introduce strict limits on the amount of time they are continuously on the computer. It is also a good idea to have the child’s vision checked some time in early primary school to exclude any refractive error that can contribute to eye strain. The work station should also be checked, with attention given to raising the height of the seat so the child can work in a more comfortable position.

Tips for managing and avoiding computer vision syndrome
Owing to the fact that computer vision syndrome refers to a range of complaints associated with computer use, its management is multifaceted.

People who work on a video display terminal and easily feel tired or uncomfortable should have a vision test to check for refractive errors. Even if glasses are already being worn, they may not be the correct power for the particular distance of the computer monitor. This is especially important for the presbyopic patient. A computer is often placed at an ‘intermediate’ distance, in between a normal reading distance and the far distance. For some presbyopes, glasses for intermediate distance in addition to the normal bifocals may therefore be necessary. Occasionally a latent squint is detected and if necessary the situation may be improved with special prism glasses.

For comfortable use, the computer display should be suitably positioned. Ideally, the top of the screen is placed just below the viewer’s eye level, and tilted slightly upwards. This allows a comfortable view in slight downgaze which may help with near focusing. Environmental lighting issues are also important. When working on a computer, people should avoid facing an unshaded window, because the much brighter background would make it difficult to view the display screen. On the other hand, sitting with the back to the window with bright light shining on the screen can cause reflections. Use shades or curtains to control the amount of light entering the room.

Eye dryness often exacerbates the tired feeling many patients experience. Apart from reduced blinking, the typical office is air conditioned with very low humidity. Using artificial tears helps greatly, as does the slightly lower computer screen since the upper eyelids are lower in downgaze and the eye is less exposed to the environment.

Finally, it is a good idea to take short breaks from working at the computer. During these breaks looking out a window or closing the eyes for a few minutes rests the ciliary muscles of the eye responsible for focusing. Blinking or closing the eyes replenishes the tear film. Fortunately, despite the multitude of symptoms associated with computer use, relatively simple steps can alleviate most of the problems and the problems are generally temporary in nature.

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