Over the past few years there has been a rapid increase in the number of people using visual display units (VDUs)/terminals (VDTs) both at home and at work. The introduction of VDUs, whilst having many advantages, has unfortunately also created concern about their use and possible health hazards.
The various health risks that are associated with the use of VDUs and that may affect the eyes are:

Asthenopia/eye strain;
Facial rash/dermatitis;
Epilepsy-photosensitive type;
Radiation.


[center]Asthenopia[/center]
Asthenopia is a very common complaint amongst VDU operators. Some studies have estimated that up to 40 percent of VDU operators suffer daily from asthenopic symptoms. The symptoms of asthenopia may be ocular, visual, systemic or functional. The ocular symptoms are sore, tired, tender, itchy, dry, burning, throbbing or aching eyes. The usual visual symptoms are focusing problems, blurred or double vision and fixation problems.

The systemic symptoms are headaches and tiredness while functional symptoms include behavioral changes.
VDU operators have a task that makes severe visual demands and, hence, it is not surprising that there are complaints of asthenopia. One possible reason for the asthenopia is uncorrected refractive errors. It has been estimated that about 30 percent of the clerical workers have uncorrected or inadequately corrected visual defects. Asthenopia is also frequently caused by convergence and accommodation difficulties. Convergence insufficiency and low fusional reserves have been found to be a major cause of asthenopia among VDU operators.

Copy typists have a very visually demanding task. Reports indicate that they are more likely to complain of asthenopia than operators using only a VDU. It has been found that some copy typists prefer to view the copy from the right rather than the left side because their binocular co-ordination and binocular stability are better in this viewing direction. While reading, a person tends to take a head orientation that will bias the position of the text slightly to the right of the median plane. If, therefore, the text to be copied is placed in any other position, the binocular stability may well be affected. It should also be noted that convergence is held more easily below the horizontal than above. Hence the screen and document holder should be situated below eye level.

It has been observed that the length of time spent by an operator at a VDU affects the incidence of asthenopia. Increasing the time spent on the VDU from 3.5 to 6 hour produced an increase from 9 to 45 percent in the number of operators reporting symptoms. This represents a five-fold increase in the number of people with problems, which were caused by less than twice the amount of exposure. Frequent work breaks are strongly advised to reduce the incidence of asthenopia, especially for operators who have no variation in tasks during the work period.

Factors such as general fatigue, I'll health, the use of certain drugs and a tendency to migraine and photophobia are some of the physiological factors that may contribute to symptoms of eye strain. Psychological factors, such as nervous or anxious personality, level of stress, motivation, and interest in the work may also be associated with eye strain. Although these personal factors may increase the risk of asthenopic symptoms arising, the physical factors of the environment and task are generally the main cause.

Several studies have investigated stress among VDU operators. Stress commonly arises when the person's perception of their own abilities are not matched by the job's demands. This is a frequent complaint reported by VDU operators, who perform repetitive, monotonous tasks. To minimize stress for the VDU operators, the task should therefore be designed to avoid or reduce repetitive elements by introducing variability in the workload, instead of long periods of concentrated work. Ideally, the change from conventional office handling routines to VDU-based systems should provide an opportunity to experience job satisfaction by removing the repetitive, simple tasks.
Watchout for part II

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