Video Displays, Work, and Vision (1983) / Chapter Skim
Currently Skimming:
1. Summary of Findings
1. Summary of Findings
Pages 5-29
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From page 5... ...
Workers and union representatives around the world have expressed concern that harmful effects may result from working with VDTs (see, e.g., Bergman, 1980; New York Committee for Occupational Safety and Health, 1980; Working Women, National Association of Office Workers, 1980; DeMatteo et al., 1981; Canadian Labour Congress, 1982~. Much of this concern has involved visual functions, human factors, 2 radiation, and tVDTs are devices for visually displaying (with symbols, graphics, or both)
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From page 6... ...
However, because factors that affect operator comfort and performance cannot be elucidated by analyzing only the optical characteristics of VDTs, relevant human factors and psychosocial issues are also considered. Because much of the concern about the possibility of radiation hazards has been based on misinformation, we analyze the results of surveys in which the levels of radiation have been measured and compare those levels with ambient levels of radiation emitted by human-made and natural sources and with current standards for occupational exposure.
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From page 7... ...
Chapter 7 explores what is known about the causes of ocular discomfort and difficulties sometimes reported with vision and discusses the limited efforts that have been made to compare visual tasks in jobs that involve VDTs and jobs that do not. Chapter 8 discusses the influence of job design and organizational factors on the well-being of VDT workers.
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From page 8... ...
These jobs, of course, differ greatly on many dimensions: in the function of the VDT within the job as a whole, in the amount of time the worker spends on tasks in which the VDT is directly involved, in the visual tasks required, etc. It seems likely that the nature and incidence of visual and other problems would vary greatly among diverse VDT jobs; thus, generalizations should be made with caution.
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From page 9... ...
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From page 10... ...
FIELD STUDIES OF VDT WORKERS AND WORKSTATIONS Studies of Radiation Emission from VDTs Video display terminals are designed to emit visible radiation (light) , but in the process of producing visible light small amounts of several other types of electromagnetic radiation are also
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From page 11... ...
Grouping of keys generated, particularly X radiation and radio frequency radiation in the 15-125 kHz frequency range. In response to concerns expressed by VDT operators and labor representatives that radiation emitted by VDTs might be harmful, field surveys and laboratory studies of radiation emissions from VDTs have been conducted over the last several years by government agencies in the United States and Europe and by private organizations and independent groups (see references in Chapter 3~.
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From page 12... ...
Standards for occupational exposure to radiation are based on existing knowledge of both acute and long-term biological effects, and they take into consideration the cumulative exposure of workers to various human-made and natural sources of radiation. There is an enormous literature on the biological effects of radiation (reviews are cited in Chapter 3~; we found no evidence to suggest that levels of radiation emitted from VDTs might produce harmful effects.
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From page 13... ...
The ten anecdotal reported cases of cataracts among VDT workers do not suggest an unusual pattern attributable to VDT work: six of the cases appear to be common, minor opacities not interfering with vision, and each of the remaining four cases had known, preexisting pathology or exposure to cataractogenic agents. Two pilot epidemiological studies that include analyses for cataract were underway at the time this report was written.
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From page 14... ...
Field Surveys Based on Self-Reports of VDT Operators Several studies have been published in which surveys of VDT operator complaints were reported. The findings and conclusions of these surveys and of several experimental studies have been widely cited, especially in nontechnical articles, as evidence that VDT work causes visual problems.
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From page 15... ...
We suggest that if future surveys are conducted, they should be designed to compare explicitly the relative influences on worker complaints of interacting variables such as job and employee characteristics, workstation design, and display image characteristics. EQUIPMENT AND WORKSTATION DESIGN VDT Design and Display Quality Although well~esigned video displays are available, many displays in commercial use employ components similar to those in home television receivers, which can be inexpensively manufactured and purchased.
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From page 16... ...
convention of calling light characters on dark background positive contrast and calling dark characters on light background negative contrast. (This is different from the European convention of calling light characters on dark background negative presentation and calling dark characters on light background positive presentation.)
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From page 17... ...
Many problems related to lighting in VDT workplaces have been caused by the introduction of VDTs into offices in which the lighting was originally designed for traditional desk-top work. The design of most VDTs creates new geometrical relationships between working surfaces and light sources and, unless appropriate modifications in workplace lighting are made, operators may experience problems with glare, images reflected by the VDT screen, and reductions in visibility of the display image.
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From page 18... ...
Studies of the effects of reflected glare on performance in nonVDT tasks have shown that even when the visual discomfort produced by reflected glare is slight, reflected images of the glare source may lead to decreases in performance because they are distracting or annoying. If the reflected image is to the side of and much brighter than the display image, it may elicit a phototropic fixation response in which an operator's eyes move away from the display image toward the reflected image.
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From page 19... ...
Approximately one-half of the surveys have compared the incidence of muscular discomfort in VDT operators with that in workers in non-VDT jobs. Some studies have also compared the incidence of discomfort in specific parts of the body in VDT and non-VDT workers.
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From page 20... ...
. The optical correction for near work routinely provided presbyopic people is likely to be inappropriate for the distances at which VDT screens are usually viewed.
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From page 21... ...
There has been little effort, however, to interview workers in depth to obtain a detailed characterization of reported symptoms or comparisons of symptoms among VDT and non-VDT workers. It would be useful to know which aspects of visual tasks might contribute to the experience of ocular discomfort sometimes reported by VDT workers and non-VDT workers and how this experience might be affected by the nonvisual features of a work situation.
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From page 22... ...
The oculomotor changes reported to follow VDT work are consistent with a larger body of research in which such changes are commonly found following periods of performing various near-visual tasks. The relationship of these changes to the subjective experience of ocular discomfort is poorly understood.
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From page 23... ...
None of the studies of VDT workers has provided valid evidence of ocular diseases or abnormalities that can be attributed to VDT work. Several surveys of VDT operators have included tests of such visual functions as acuity, astigmatism, stereopsis, phoria, and color vision.
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From page 24... ...
A few studies have attempted to identify psychosocial stressors in VDT work and to relate them to self-reports of employee well-being and in some cases to physiological changes such as increased blood pressure. Although some studies have found that VDT operators report high levels of job-related stress, no psychosocial stressors or health-related outcomes have been shown to be unique to work involving VDTs.
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From page 25... ...
Two kinds of person-environment fit, which may not always represent two mutually exclusive classifications, can be examined: one is the fit between a worker's needs (or preferences, desires, values, etc.) and the related supplies for these needs in his or her job environment; the other is the fit between a worker's abilities and the demands of his or her jObe This person-environment fit approach has not yet been applied to work involving VDTs, but it has been applied to the study of stressors in other work situations, and it can provide a useful conceptual framework in which to study possible psychosocial stressors in VDT work.
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From page 26... ...
It is likely that problems with and concerns about the use of VDTs would be greatly alleviated by the appropriate application of this know 1edge to the design of VDT equipment and VDT jobs (see Chapter 9~. We strongly urge designers of VDT jobs to draw upon wellestablished principles for organizing work in ways that are
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From page 27... ...
Among the implications of these principles is that flexibility is preferable to fixed rest breaks. It should be noted, however, that rigidly designed jobs with high quotas for productivity, in which the output of workers is monitored moment by moment, allow little or no flexibility; in these cases, fixed rest breaks may provide the only opportunity to move around or to rest tired eyes.
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From page 28... ...
Some standards cover workstation design features, image display characteristics, and lighting and reflection conditions; some also specify provision of rest breaks, operator training in VDT use, and eye examinations for VDT operators. Most, though not all, standards specify numerical values for such parameters as display character size, luminance levels, key force, and viewing distance.
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From page 29... ...
Objective measures that can be used to relate visual discomfort to patterns of visual activity, VDT characteristics, and visual performance are needed. Such research would be relevant to an understanding of performance of a range of near-work tasks in addition to VDT work.
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