Click for next page ( 215


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 214
10 Research Needs In the preceding chapters we have emphasized slur conclusion that application of existing knowledge would reduce the incidence of complaints and symptoms of jo~related ocular and rrPusculo- skeletal discomfort and stress reported by VDT workers. In addition, however, a number of questions raised in our analysis of the research literature on effects of VDT work remain unan- swered and merit attention. Many of these questions could be answered by appropriately designed research, and in this chapter we suggest several lines of research that might be useful. How- ever, we urge that competing priorities in the field of occupa- tional health be carefully considered before undertaking research on VDT work. EFFECTS OF DISPLAYS ON VISUAL ACTIVITY Objective Correlates of Visual Complaints A programmatic research effort should be oriented toward relat- ing objective measures of visual activity to subjective complaints of ocular discomfort and visual difficulties. Much of the diff~- culty in conducting or evaluating such research stems from the poor definition of 'visual fatigue" and the lack of established correlations among measures of ocular discomfort, visual per- formance, and physiological variables. Studies should be con- ducted to measure visual functions, such as eye movements (e.g., frequency and duration of fixations and saccades, scan patterns) and changes in pupil size and accommodation, and to relate these measures to visual symptoms reported by subjects. Since eye- movement patterns have been related to display quality by several research efforts, it seems logical that measures of visual activity 214

OCR for page 214
215 could be related to subjective symptoms in a realistic working environment. The displays used in this research should be system- atically varied, from those that are considered to be of poor quality to those that are considered to be of good quality. Useful optical measures of image quality have been defined by several investigators (see Chapter 4~. It is extremely important that such research be conducted using longitudinal designs and that workers should be studied while spending considerable time performing meaningful, realistic tasks that might induce visual symptoms. Brief laboratory studies of the type often used in research on visual performance are not adequate to address questions in this area. With this approach it should be possible to relate the quality of a displayed image to measurements of visual functions and to such subjective symptoms as ocular discomfort. Relating Display Characteristics to Workplace Conditions Research is needed to relate display design characteristics to workplace illumination and the effective suppression of glare. After first doing everything possible in the workplace to eliminate sources of direct and indirect glare or to reduce their effects, two further approaches to suppressing glare should be studied: use of glare-reduction filters and changes in display image polarity. The effectiveness of filters should be measured as a function of environmental parameters, such as types of glare and location of glare sources. The effects of various types of filters on image quality and contrast transmission should be measured to deter- mine whether visual task performance is actually improved by a given filter type in a given environment. This research is criti- cally needed to cut through the morass of arbitrary, capricious, and often misleading claims made by some filter manufacturers. Careful research is needed to compare the effects of positive- and negative-contrast displays on visual task performance and visual symptoms. Because a negative-contrast display probably requires different refresh rates, different stroke widths, and different contrast ratios than does a positive-contrast display, a moderately large investment would be necessary to achieve the equipment control required for this research. Once the control over such equipment is obtained, however, the research could be conducted in the same environment used to measure visual activity, visual performance, and subjective estimates of discomfort, as described above.

OCR for page 214
216 Effects of Image Instability Research is needed on the possible effects on visual function caused by geometric and positional instability of display images. The frame-to-frame jitter of a CRT image, however small, may cause visual difficulties, especially during prolonged viewing. Comparisons between representative CRT displays and geometri- cally stable (e.g., flat-panel) displays would permit an evaluation of possible effects. Here, too, research should be conducted using realistic task conditions and long enough viewing times to induce symptoms. Distinguishing Specific Effects of VDTs Visual complaints and symptoms should be examined as a function of work time for various segments of the working population. Work is inherently tiring, and visual work may be inherently visually tiring. Thus, it is important that the time course of visual complaints and symptoms be accurately measured for a variety of displays, to distinguish the effects of visual work from the effects of visual displays per se. This research should use various representative segments of workers, including those with good and those with poor eyesight and younger as well as older workers. PSYCHOSOCIAL STRESSORS Our review of the published literature on psychosocial stressors in VDT work reveals many questions that have not been adequately addressed: How should VDT work be characterized and how could its characteristics be reliably measured? What psychosocial Variables of work should be measured in VDT studies7 What physical conditions of work settings need to be measured and controlled in the study of psychosocial stressors in VDT use? Does the amount or kind of VDI use increase or decrease some psychosocial stressors, such as isolation from others? What parameters of rest periods (e.g., duration, frequency, spacing, flexibility) should be studied in relation to worker well being? To what extent is well-being influenced by the manner in which VDT technology is introduced into the workplace? We caution, however, that the payoff for research on questions about psychosocial stressors unique to VDT work seems likely to be low. Given the flaws in existing studies, it cannot be deter- mined whether most of the differences reported between VDT work and non-V DT work are attributable to the use of VDT

OCR for page 214
217 technology Par as. Aspects of work such as workload, social support, and task complexity that are not specific to VDT work have been confounded with aspects such as display design that are specific. The nonspecific aspects have clearer empirical links to mental and physical wellbeing than does the use of VDTse Consequently, we suggest that higher priority be given to studies of parameters such as workload, social supped Id task complexity that affect ~ icbs' not lust those involving VDTs.

OCR for page 214