The introduction of Visual Display terminals (VDT) in offices has further limited the number of postures permitted to the clerical employees in traditional office work. National Institute for Occupational Safety and Health (1981) suggests that operator in VDT jobs that are characterized by high pressure to perform and low control over the task, report, more visual and muscular discomfort then do operator whose job allow greater autonomy and flexibility. VDT's are often designed and introduced into offices without the application of relevant human factors designed principles. The user is completely overlooked and computers are placed on conventional office furniture formerly used. Operators are often required to work in cramped spaces that leave them little room to place document holder or manuscript in position. Operators in such situation are likely to experience visual discomfort, muscular discomfort and fatigue. The situation is still worst for older workers, because of visual changes such as presbyopia and increased glare susceptibility; they also become quite vulnerable to problems of poor workstation design. The optical correction for near work routinely provided for bifocal spects bearer is not appropriate for the distance at which VDT screen is normally visualized. In order to view the screen, the worker with bifocal spects, must tilt his or her head backwards to look through the bottom part of the spects. More than six per cent of the total body weight is concentrated in the head; and if head is bent backward sufficiently to bring the eyes into the required viewing position, the static activity of neck muscles required to hold it in place leads to fatigue and strain. Continuous bending of head on the backside also causes stress on the vertebral column ultimately leading to "spondilysis". This necessitates a through analysis of existing VDT station so that a proper VDT work station can be developed which will be appropriate and natural for man-machine-environment system and which will also allow comfortable posture and greater efficiency by the human being. This study proposes to redesign the VDT workstation for bifocal operators considering the physical, biomechanical, physiological and psychological limits in conjunction with VDT keyboard, source document along with working environment. The purpose of the study is to perform an in-depth ergonomic evaluation of visual display terminal workstation for the people wearing bifocal lenses and to fulfil the following objectives: 1. Evaluation of the present working posture adopted by bifocal people while working on computer. 2. Evaluation of existing VDT workstation on the basis of different body dimensional and biomechanical requirements along with comfort ability and ease of operation of the VDU operator. 3. Find out criteria for redesigning of computer workstation for bifocal people.
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