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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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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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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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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:
visual function
