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Executive Summary The issues we were requested to address in this study are presented in the preface. Our findings and conclusions respond both to these issues and to related issues and concerns that we considered in our work. Although much has been written in the last several years about the problems and concerns of people who work with video display terminals (VDTs), the literature has been based predominantly on a small number of studies, many of which have substantial short- comings in methodology that severely limit the conclusions that can appropriately be drawn from them. In addition to reviewing that literature, we have drawn upon substantial technical litera- tures on visual function, image quality, lighting design, ergonomic design, and industrial and organizational psychology. To a large extent our conclusions are based on these more extensive and better validated literatures. 1. Surveys of workers who use VDTs indicate that complaints and symptoms of jo~related ocular discomfort, musculoskeletal discomfort, and stress are common. Surveys that have included comparison groups of non-VDT workers suggest that the frequency of such complaints is greater among workers who use VDTs than among those who do not. Most surveys, however, have been poorly designed, and the inferences that may reasonably be drawn from them are suggestive rather than conclusive. Surveys have not established whether complaints and reported symptoms are related to VDT characteristics, other aspects of the workplace and job situation, or some combination of these factors. Most studies have not adequately considered the heterogeneity of VDT job situations. Evidence suggests that job design and task require- ments can produce jo~related physical symptoms and stress. Thus it is possible that differences in reported symptoms between VDT workers and non-VDT workers might be more directly related to characteristics of the work situation--i.e., the way in which
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2 VDTs are used--than to characteristics inherent in VDTs. Given the lack of adequate controls in survey studies, the relative influence of equipment characteristics and job characteristics remains an open question. 2. The comfort, performance, levels of stress, and job satisfaction of workers who regularly use VDTs have in many cases been adversely affected by failure to apply to jobs and equipment well-established principles of good design and practice. A considerable literature exists on the effects of image display characteristics on legibility and user performance, and well-des~gned, high~uality VDTs are available commercially. In many instances, however, VDTs have been designed without attention to existing scientific data on image quality, and many VDTs on the market do not provide the legibility of high~quality printed material. In addition, in many instances VDTs have been introduced into workplaces with little attention to principles of human factors, illuminating engineering, and industrial and organizational psychology. We strongly recommend that manu- facturers and users of VDT equipment draw upon available scientific data in designing and selecting VDT equipment and in designing VDT-related work. 3. The terms visual fatigue and eyestrain are frequently used in ill-defined and differing ways. These terms do not correspond to known physiological or clinical conditions. We suggest instead that researchers and others use terms that specifically describe the phenomena discussed, such as ocular discomfort, changes in visual performance, and changes in oculomotor functions. 4. The symptoms of ocular discomfort and difficulty with vision reported by some workers who use VDTs appear to be similar to symptoms reported by people performing other near-visual tasks. Temporary changes in measures of visual function reported to occur following VDT work appear to be similar to those observed after performance of near-visual tasks in non-VDT jobs. Most features of VDT work tasks that may contribute to discomfort or visual difficulty are also found in various jobs not involving VDTs; however, poorly designed VDTs, workstations, and work tasks, often produce a particularly problematic concatenation of adverse features. 5. It is not known whether ocular discomfort and reported changes in measures of visual function are related. In general, the physiological and psychological mechanisms underlying ocular discomfort are poorly understood. However, there is no scien- tifically valid evidence that ocular discomfort or temporary
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3 changes in visual functions are associated with damage to the visual system. 6. A number of competent studies have found that the levels of radiation emitted by VDTs are far below current U.S. occupa- tional radiation exposure standards and are generally much lower than the ambient radiation emitted by natural and human-made sources to which people are continuously exposed. We have not attempted to evaluate the adequacy of existing standards, but our review of the scientific literature on biological effects of radia- tion indicates that the levels of radiation emitted by VDTs under conditions of normal operation and under conditions of malfunc- tion or aging of the VDT are highly unlikely to be hazardous. These considerations suggest that routine radiation surveys of VDTs in the workplace are not warranted. However, radiation testing of new VDT models should be continued to ensure that product safety standards are met. 7. We find no scientifically valid evidence that occupational use of VDTs is associated with increased risk of ocular diseases or abnormalities, including cataracts. Existing knowledge makes such an association seem quite unlikely. Only if competent pilot studies were to indicate such an association would large-scale epidemiological studies of cataracts among VDT workers be warranted. 8. We find no scientifically valid evidence that the use of VDTs per se causes harm, in the sense of anatomical or physio- logical damage, to the visual system. There is nothing in the literature on the effects of working with VDTs, or in the broader realm of existing scientific and clinical knowledge, that suggests that such a causal relationship is likely. 9. It is difficult for manufacturers, purchasers, and users to make meaningful comparisons between VDT products because techniques for measuring image characteristics and evaluating quality have not been standardized and applied in commerce. We recommend that efforts be made to standardize measurement techniques. Characteristic measures of products should be made routinely available to purchasers and users. 10. Existing data do not provide a sufficient basis for estab- lishing mandatory standards for display, lighting, and workstation parameters or for task designs and work schedules in VDT-related work. Research is needed to provide adequate data that can be used as a basis for decisions regarding standards. In the mean- time, application of well-established principles of good design and
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4 practice can be expected to reduce the incidence of complaints of work-related physical symptoms and stress and to enhance the comfort and performance of workers. 11. Carefully designed research on the effects of VDT characteristics on visual performance and comfort would be useful, especially in view of the projected increase in the number of workers who will be using such equipment in the future. Research on psychosocial parameters that affect all jobs, such as workload, task complexity, and social support, would seem to offer more potential benefit than research on psychosocial variables specific to VDT work. We emphasize, however, that application of existing knowledge in designing and using VDTs should be given high priority.
Representative terms from entire chapter: