My question relates to computers: Most people sit 18 inches
from the screen and if they are anything like me they spend
many hours at day at it. Is there any evidence that this may
damage your eyes in any way. I know I experience eye fatigue.
I don't know whether or not I am doing any permanent damage.
Recommend, if you can, prudent behavior in this area.
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Answered by Richard E. Gans, M. D.
The best recent review of the effects of VDTs on visual function appeared in "Survey of Ophthalmology" (Vol.33, Number 6, May-June, 1989). Despite the lack of solid scientific evidence in some areas, several specific conclusions were reached and will be summarized here.
1. Electromagnetic radiation emitted from currently available VDTs is well below occupational health standard safety levels. The only exception to this is if color television sets, built before 1970, are used in place of a computer monitor. They may emit radiation in excess of these standards. Newer color TV sets and monitors designed for computer use do not pose a threat, according to the authors. Thus, the risk of significant eye injury from emitted radiation is very low.
2. There is no reliable, scientific evidence to show that VDT users are more prone to cataract formation or any other organic disease of the eye than the general public.
3. The symptoms of eye fatigue, burning, and discomfort are not due to pathologic changes in the eyes; rather, they are related to lighting, glare, and poor VDT image quality. Depending on the particular study, between 45 and 94% of VDT operators described adverse visual symptoms, which seemed to correlate with the daily duration of VDT use.
In general, the suggestions to prevent and alleviate adverse visual symptoms revolve around ensuring that pre- existing ocular problems are corrected, optimizing ambient lighting conditions, using quality VDTs and designing work stations to prevent poor working positions.
The monitor image must be focused properly. For some individuals, this might require a separate pair of prescription glasses designed solely for use with the computer. By measuring the distance between the monitor and the user's eyes, the proper change in the glasses prescription is easily calculated. Those individuals who wear bifocals or trifocals might need to have the position of these lenses (or the position of their monitor) adjusted for optimal comfort.
Lighting in the room can be designed to ease eyestrain. Lights should not reflect off the surface of the monitor. Ambient lighting should be reduced. Lighting should originate above or behind, but not from in front of, the computer operator.
Eye symptoms are worsened considerably if the monitor image is of poor quality. Screen flicker, poor image quality, coarse resolution and improper color mixing are common causes of eye discomfort.
There is certainly a great deal of anecdotal evidence that suggests that body and head position must be optimized if an individual is to use a computer comfortably for extended periods of time. In addition to nuisance types of discomfort, serious injuries such as repetitive action injuries (eg. carpal tunnel syndrome) can result from improper body ergonomics.
It has been suggested that since viewing a VDT significantly lowers the rate of blinking and since evaporation off the ocular surface is increased between blinking, that the ambient relative humidity should be maintained at a higher level than normal in an attempt to aid ocular comfort. The intermittent use of lubricating eye drops during extended periods of computer use may also provide relief from eye discomfort.
There are a variety of glare shields that can be placed in front of the VDT, as well as coatings which can be applied to the users glasses to minimize glare and reflections. None of these has been proven effective in controlled studies to prevent ocular symptoms. Nevertheless, many are in use and coatings are available in specific colors to match the type of VDT being used:
Blue coating -> monochrome amber screens
Violet coating -> monochrome green screens
Gray coating -> black and white screens.
PLEASE NOTE: The information contained on this system is not intended to supplant individual professional consultation, but is offered as a community education service. Advice on individual problems should be obtained directly from a professional.
Copyright, 1994. Richard E. Gans, M.D.
Last Modified: August 23, 1996