The major objective of this research is to study the occupational hazards of people working with Video Display Terminals (VDTs). The introduction of VDTs in the work place has brought about increased visual complaints such as eye strain, eye soreness, blurred vision and headache. Eye strain is defined as a kind of visual discomfort that occurs due to prolonged study of visual details with reduced eye movements. As this is one of the major problems reported by millions of people working with VDTs world over, studies on eye strain due to continuous exposure to VDT have gained importance. An experimental investigation has been made to study the effects of the viewing angle and distance of users from the VDT, time of exposure, illumination level and font size, on eye strain. The optimal values for these factors on eye strain have been determined.
Video Display Terminals (VDTs) have attained great importance in the modern work environment as an interface between the operator and the computer, though not without problems. Computer usage being a visually demanding task, vision problems have become very common in today's workplace. Problems related to vision occur in about 75 to 90% of all VDT users. Some of the subjective complaints of the VDT users are pain in the eyes, headache, blurred vision, dry and irritated eyes, sensitivity to light, double vision, boosted fatigability, back pain, neck pain and pain in the wrist and fingers. It can be seen that about two-thirds of the complaints are those related to vision (see Figure 1 response graph for more details).
Asthenopia is the term used by eye professionals for eye strain. Generally, asthenopia may be a result of such problems as focusing spasm, different vision to each eye, astigmatism, hyperopia (far-sighted), myopia (near-sighted), excess light, voluntary focusing, eye coordination difficulties, etc. (Miller, 1984). In the VDT environment, eye strain can be caused by a number of different environmental and visual conditions such as poor VDT design and orientation, improper lighting, time of exposure, type of task, reduced screen contrast and excessive glare. It is caused due to prolonged attention of visual details with restricted eye movement in a VDT field. Tasks which require frequent changing of the direction of gaze at different distances, may increase the likelihood of such problems. |
