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The incidence and importance of eyestrain among VDU operators
terms, a mortality rate of about 47 per 100 000 of population, and a morbidity rate of about 2000 per 100 000. These high rates identify a massive failure of existing systems to grapple with the modern public health problem of trauma. This paper suggests that existing compensation systems, essentially derived from the fault doctrine, have acted as a major handicap to the development of more effective preventive measures. It is suggested that, in some cases, compensation acts as a disincentive to preventive initiatives; that, in other cases, it inhibits preventive activities directly; and in most cases it is wasteful of limited resources which could more profitably be utilised for preventive work. The major criticism, however, is directed at the way in which the fault doctrine has promoted an outmoded and unscientific approach to trauma. A more modern approach, conceptualising trauma as a public health problem and utilising the developing knowledge of the ergonomist is discussed, and the principles of effective countermeasure development are outlined. Some desirable developments are also suggested.
Visual processes in man 11,2.6 (??993) Simmons, R.R., and Kimball, K.A. Operator visual workload shifts as a function of vehicle stability. In: Compass for Technology, Proceedings of the 23rd Annual Meeting of the Human Factors Society, Boston, Massachusetts, 29 O c t - 1 Nov 1979, Edited by C.K. Bensel pp 3 5 2 - 3 5 6 . This research was initiated to compare the visual performance/ workload of pilots during fixed wing and rotary wing flights. The corneal reflection technique was used to obtain the visual data. The results demonstrate that visual performance/ workload of the pilots was different for each aircraft. Because the major difference between the aircraft was the aerodynamic stability, it was assumed that the visual workload was in fact a function of aircraft stability. The overall purpose of such research has been to provide information concerning pilots' visual requirements for safe mission accomplishment. 11.2.7 (78006)
Lindskoog, H. Work at visual display units: Who needs special glasses for work at cathode ray terminals? (Arbete vid Bildskarm: Vem Behover Sarskilda Terminalglasogon?). (In Swedish.)
106
AppliedErgonomics June 1980
Arbetsrniljo, Jan 1979, No 1, 15-20. Abstr in: CIS Abstracts (CIS 79-1009). The survey used as a basis for drafting Directive No 136 of the Swedish National Board for Occupational Safety and Health concerning the prevention of visual disturbances in cathode ray terminal work showed that 54"8% of CRT display terminal operators complained of these disturbances. This article gives advice on the recruitment of CRT operators, with early screening for refractory disorders and complete eye examination. Adaptation of prescription lenses presupposes the precise determination of the distance between the eyes and the distance between the lens and the pupil. When adapting the frame, the angle of vision should be taken into account, because selecting the wrong angle would result in prismatic deformation of the image, usually causing headache. The advantages and disadvantages of multifocal and progressive lenses are considered, and the importance of close collaboration between the ophthalmologist, the optician and the health and safety officer.
Central processes in man 11.2.8 (78018)
Wagenaar, W.A., and Visser, J.G. The weather forecast under the weather. Ergonomics, Aug 1979, 22.8,909-917. The weather forecast as broadcast several times a day appears to be too long for effective storage in human memory. Out of 12 to 32 items per message a maximum of seven (+ 2) were reproduced. Selective listening to parts of the message reduced the number of correctly recalled items to about five. Addition of a long-term weather forecast has the same interfering effect as increase of list length. The results are discussed on the basis of the observation that weather forecasts are processed in the same way as nonsense materials are. Improvement of the situation might be obtained by making weather forecasts more meaningful. 11.2.9 (78035)
Megaw, E.D., Alexander, C.J., and Richardson, J. Fault mix and inspection performance. International Journal o f Production Research, May/Jun 1979, 17.3, 1 8 1 191. Eight subjects performed a paced conveyor inspection task of small zinc-plated washers. There were two
fault types, one considerably more difficult to detect than the other. Each fault type had a probability of occurrence of 0'0, 0"025 or 0"05 providing eight differetat batch conditions, four where only one fault type was present and four where both were present. All subjects were tested twice on each of the eight conditions. There were 1800 washers in each batch condition, which were inspected at a rate of 3/s. The results demonstrated that the probability of detection of either fault type was significantly reduced when subjects were searching for the two fault types simultaneously, the decrease in probability being greater the larger the a priori probability of the other fault type. Signal detection theory analysis suggested that these results were due to changes in sensitivity rather than in response bias. The classical vigilance effect of signal probability was not observed.
F actors affecti ng perceptual-motor performance 11.2.10 (78074) Cakir, A. The incidence and importance of eyestrain among VDU operators. Paper presented at the Ergonomics Society One-Day Meeting on Eyestrain and VDUs, Loughborough, 15 December 1978, 8 pp. The Institute of Ergonomics of the Technical University of Berlin has recently completed a study for the Ministry of Labour of the Federal Republic of Germany. One of the aims of this study was to identify the parameters of VDUs and work places utilising VDUs relevant to eyestrain. The study has shown that: eyestrain is one of the most significant problems of working with VDUs but there is no objective measure of eyestrain, eyestrain (subjectively measured) is highly correlated with the optical properties of displays but also highly correlated with the optical properties of paper manuscripts and keyboards even when used by skilled typists. The study has also shown that there is a significant correlation between eyestrain, back ailments and headaches. By using VDUs of poor optical quality one can cause not only fatigue through eyestrain but also permanently damage the spine. It could also be shown that users with spectacles corrected to 330 mm viewing distance suffer more back ailments than normal sighted persons (49% of the subjects with 330 mm corrected spectacles had received treatment for various back ailments compared with 30% of normal sighted subjects).
Complaints of eyestrain differ widely between different jobs. Programmers or journalists with more satisfactory jobs and shorter periods of working with VDUs react more positively to them than typists or clerks who work with VDUs continuously.
for VDU operators issued by the Printing Industries Committee of the Trades Union Congress, recommending as a minimum at least a 30 min break after every period of 2 h work at a VDU.
11.2.11 (78075)
11.2.13 (78078) Stewart, T.F.M. Review of VDU ergonomics. Paper presented at the Ergonomics Society One-Day Meeting on Eyestrain and VDUs, Loughborough 15 December 1978, 12 pp.
Forsberg, K. Ergonomics of visual and muscular work at CRT terminals (Synoch Muskelergonomi vid Bildskarmsarbete). (In Swedish.) Arbetsmil]o, Nov 1978, No 14, 1 9 - 2 1 . Abstr in: CIS Abstracts (CIS 79-865). This article gives the results of several surveys carried out in the UK and in other European countries concerning the hazard of eye strain and other eye disorders associated with work at CRT terminals. A survey was carried out in Sweden to ascertain the factors in this work which cause visual and muscular fatigue. Environmental conditions which increase visual effort and may result in muscular fatigue (eyes, nape of the neck, shoulders, back) are set out in synoptic tables indicating suggested solutions: problems linked to the way in which the information is displayed on the screen, keyboard layout and design, condition of MSS to be keyed in, uncorrected defective vision, lighting, layout, design and microclimate of work premises, workplace layout and design (operator's seat, desk or table, dimensions, etc). Medium-term future trends in the use of CRT terminals, showing the importance of the ergonomic design of these workposts. 11.2.12 (78076) Gilbert, P. Visual display units - are they safe? Occupational Health, Aug 1978, 3 0 . 8 , 3 5 7 - 3 6 3 . Abstr in: CIS Abstracts (CIS 79-844). This article, by the Principal Medical Officer of the Occupational Health Service, British Post Office Telecommunications, gives background information on the design and development of visual display units (VDUs), foUowed by considerations on: real and doubtful health problems (possibility of ionising or non-ionising radiation from defective equipment: visual fatigue; subjective symptoms such as headache, irritability, nausea, anxiety, depression, etc); eye strain due to wearing spectacles of focal length unsuited to the distance from the screen; ergonomics aspects; current research (including a 5-year investigation commenced in 1977 by the British Post Office). Immediately following the article is a commentary by a VDU operator which endorses the guidelines
longitudinal studies in order to assess the true effects of stressful influences.
Physiology, anthropometry and biomechanics 11.2.15 (78108)
Many VDU operators experience symptoms of visual discomfort or visual fatigue which are referred to rather loosely as eyestrain. Although there are, as yet, no reliable objective measures of eyestrain, the symptoms typically reported include headaches, burning sensations in the eyes and twitching of the eye muscles. Whether or not prolonged and repeated fatigue can have any lasting effect on the individual is the subject of another paper at this conference. However, it is clear that eyestrain or visual fatigue can have a significant effect on the well being and on the performance of an operator and should therefore be minimised or eliminated where possible. The aim of this paper therefore is to identify the various factors which can cause or aggravate visual fatigue and to suggest how adequate attention to ergonomics can largely overcome the problem. 11.2.14 (78088)
Glenvflle, M., and Wilkinson, R.T. Portable devices for measuring performance in the field: The effects of sleep deprivation and night shift on the performance of computer operators. Ergonomics, Aug 1979, 22.8, 9 2 7 - 9 3 3 . The performance of 12 computer operators was measured in the field on two new portable tests of reaction time, during the first night of the night shift at 0400 h and at the beginning of the day shift (0800 h), over three successive three-week comparisons. The results were: (i) mean reaction time increased significantly on the night shift as compared with the day; (ii) the adverse effect of the night shift was absent during the first comparison and became increasingly apparent on the second and third replications. These results: (i) provide evidence of inferior performance on the night as compared with the day shift in the field; (ii) show that data from previous studies of sleep deprivation in the laboratory are able to provide a good indication of what was to be expected in the field; (iii) emphasise the need for
Oleinikov, V.A. Physiological aspects of the work of miners on working faces. Human Physiology, Sep/Oct 1978, 4 . 5 , 6 7 7 683. Working conditions in the coal industry differ in many important respects from those in other branches of the national economy; underground working, the danger factor, greater physical and neuropsychic loads. The widespread introduction of mechanisation in one of the main areas of mining, namely on the working face, has been aimed at making the work easier and increasing its productivity. Mechanised systems of the KM-87 type are most widely used in mines in the Donetsk coalfield. Walls equipped with these systems account for about 90% of the total amount of coal won from mechanised wails. However, problems of work physiology in highly mechanised working faces in coal mines have been inadequately studied and it is the purpose of this article to examine some of the features which distinguish the work of miners. Observations were made on 140 miners working on four working faces ('Voroshilovgradugol' and 'Donbassantratsit') equipped with mechanised systems of the KM-87 type. The working faces studied had a daily coal output of 600 to 2200 tons. 11.2.16 (78127)
Dorling, E. Physiological analysis of work with fork lift trucks (Arbeitsphysiologische Analysen zum Thema Gabelstapler). (In German.) Tu Jul/Aug 1978, 1 9 . 7 - 8 , 2 5 2 - 2 5 7 . Abstr in: CIS Abstracts (CIS 79-1177). Measurement methods used were pulse-rate and ECG, oxygen intake and energy expenditure, reaction time, visual flicker fusion threshold, mechanical vibration. These measurements enabled the author to evaluate the influence on the human body of power steering, a lifting mast offering a free field of vision, an adjustable steering column, more leg room and various models of drivers' seats. It appears that power steering and a hydraulically suspended driver's seat gives a higher safety factor and improves working conditions.
Applied Ergonomics
June 1980
107
Visual processes in man 11,2.6 (??993) Simmons, R.R., and Kimball, K.A. Operator visual workload shifts as a function of vehicle stability. In: Compass for Technology, Proceedings of the 23rd Annual Meeting of the Human Factors Society, Boston, Massachusetts, 29 O c t - 1 Nov 1979, Edited by C.K. Bensel pp 3 5 2 - 3 5 6 . This research was initiated to compare the visual performance/ workload of pilots during fixed wing and rotary wing flights. The corneal reflection technique was used to obtain the visual data. The results demonstrate that visual performance/ workload of the pilots was different for each aircraft. Because the major difference between the aircraft was the aerodynamic stability, it was assumed that the visual workload was in fact a function of aircraft stability. The overall purpose of such research has been to provide information concerning pilots' visual requirements for safe mission accomplishment. 11.2.7 (78006)
Lindskoog, H. Work at visual display units: Who needs special glasses for work at cathode ray terminals? (Arbete vid Bildskarm: Vem Behover Sarskilda Terminalglasogon?). (In Swedish.)
106
AppliedErgonomics June 1980
Arbetsrniljo, Jan 1979, No 1, 15-20. Abstr in: CIS Abstracts (CIS 79-1009). The survey used as a basis for drafting Directive No 136 of the Swedish National Board for Occupational Safety and Health concerning the prevention of visual disturbances in cathode ray terminal work showed that 54"8% of CRT display terminal operators complained of these disturbances. This article gives advice on the recruitment of CRT operators, with early screening for refractory disorders and complete eye examination. Adaptation of prescription lenses presupposes the precise determination of the distance between the eyes and the distance between the lens and the pupil. When adapting the frame, the angle of vision should be taken into account, because selecting the wrong angle would result in prismatic deformation of the image, usually causing headache. The advantages and disadvantages of multifocal and progressive lenses are considered, and the importance of close collaboration between the ophthalmologist, the optician and the health and safety officer.
Central processes in man 11.2.8 (78018)
Wagenaar, W.A., and Visser, J.G. The weather forecast under the weather. Ergonomics, Aug 1979, 22.8,909-917. The weather forecast as broadcast several times a day appears to be too long for effective storage in human memory. Out of 12 to 32 items per message a maximum of seven (+ 2) were reproduced. Selective listening to parts of the message reduced the number of correctly recalled items to about five. Addition of a long-term weather forecast has the same interfering effect as increase of list length. The results are discussed on the basis of the observation that weather forecasts are processed in the same way as nonsense materials are. Improvement of the situation might be obtained by making weather forecasts more meaningful. 11.2.9 (78035)
Megaw, E.D., Alexander, C.J., and Richardson, J. Fault mix and inspection performance. International Journal o f Production Research, May/Jun 1979, 17.3, 1 8 1 191. Eight subjects performed a paced conveyor inspection task of small zinc-plated washers. There were two
fault types, one considerably more difficult to detect than the other. Each fault type had a probability of occurrence of 0'0, 0"025 or 0"05 providing eight differetat batch conditions, four where only one fault type was present and four where both were present. All subjects were tested twice on each of the eight conditions. There were 1800 washers in each batch condition, which were inspected at a rate of 3/s. The results demonstrated that the probability of detection of either fault type was significantly reduced when subjects were searching for the two fault types simultaneously, the decrease in probability being greater the larger the a priori probability of the other fault type. Signal detection theory analysis suggested that these results were due to changes in sensitivity rather than in response bias. The classical vigilance effect of signal probability was not observed.
F actors affecti ng perceptual-motor performance 11.2.10 (78074) Cakir, A. The incidence and importance of eyestrain among VDU operators. Paper presented at the Ergonomics Society One-Day Meeting on Eyestrain and VDUs, Loughborough, 15 December 1978, 8 pp. The Institute of Ergonomics of the Technical University of Berlin has recently completed a study for the Ministry of Labour of the Federal Republic of Germany. One of the aims of this study was to identify the parameters of VDUs and work places utilising VDUs relevant to eyestrain. The study has shown that: eyestrain is one of the most significant problems of working with VDUs but there is no objective measure of eyestrain, eyestrain (subjectively measured) is highly correlated with the optical properties of displays but also highly correlated with the optical properties of paper manuscripts and keyboards even when used by skilled typists. The study has also shown that there is a significant correlation between eyestrain, back ailments and headaches. By using VDUs of poor optical quality one can cause not only fatigue through eyestrain but also permanently damage the spine. It could also be shown that users with spectacles corrected to 330 mm viewing distance suffer more back ailments than normal sighted persons (49% of the subjects with 330 mm corrected spectacles had received treatment for various back ailments compared with 30% of normal sighted subjects).
Complaints of eyestrain differ widely between different jobs. Programmers or journalists with more satisfactory jobs and shorter periods of working with VDUs react more positively to them than typists or clerks who work with VDUs continuously.
for VDU operators issued by the Printing Industries Committee of the Trades Union Congress, recommending as a minimum at least a 30 min break after every period of 2 h work at a VDU.
11.2.11 (78075)
11.2.13 (78078) Stewart, T.F.M. Review of VDU ergonomics. Paper presented at the Ergonomics Society One-Day Meeting on Eyestrain and VDUs, Loughborough 15 December 1978, 12 pp.
Forsberg, K. Ergonomics of visual and muscular work at CRT terminals (Synoch Muskelergonomi vid Bildskarmsarbete). (In Swedish.) Arbetsmil]o, Nov 1978, No 14, 1 9 - 2 1 . Abstr in: CIS Abstracts (CIS 79-865). This article gives the results of several surveys carried out in the UK and in other European countries concerning the hazard of eye strain and other eye disorders associated with work at CRT terminals. A survey was carried out in Sweden to ascertain the factors in this work which cause visual and muscular fatigue. Environmental conditions which increase visual effort and may result in muscular fatigue (eyes, nape of the neck, shoulders, back) are set out in synoptic tables indicating suggested solutions: problems linked to the way in which the information is displayed on the screen, keyboard layout and design, condition of MSS to be keyed in, uncorrected defective vision, lighting, layout, design and microclimate of work premises, workplace layout and design (operator's seat, desk or table, dimensions, etc). Medium-term future trends in the use of CRT terminals, showing the importance of the ergonomic design of these workposts. 11.2.12 (78076) Gilbert, P. Visual display units - are they safe? Occupational Health, Aug 1978, 3 0 . 8 , 3 5 7 - 3 6 3 . Abstr in: CIS Abstracts (CIS 79-844). This article, by the Principal Medical Officer of the Occupational Health Service, British Post Office Telecommunications, gives background information on the design and development of visual display units (VDUs), foUowed by considerations on: real and doubtful health problems (possibility of ionising or non-ionising radiation from defective equipment: visual fatigue; subjective symptoms such as headache, irritability, nausea, anxiety, depression, etc); eye strain due to wearing spectacles of focal length unsuited to the distance from the screen; ergonomics aspects; current research (including a 5-year investigation commenced in 1977 by the British Post Office). Immediately following the article is a commentary by a VDU operator which endorses the guidelines
longitudinal studies in order to assess the true effects of stressful influences.
Physiology, anthropometry and biomechanics 11.2.15 (78108)
Many VDU operators experience symptoms of visual discomfort or visual fatigue which are referred to rather loosely as eyestrain. Although there are, as yet, no reliable objective measures of eyestrain, the symptoms typically reported include headaches, burning sensations in the eyes and twitching of the eye muscles. Whether or not prolonged and repeated fatigue can have any lasting effect on the individual is the subject of another paper at this conference. However, it is clear that eyestrain or visual fatigue can have a significant effect on the well being and on the performance of an operator and should therefore be minimised or eliminated where possible. The aim of this paper therefore is to identify the various factors which can cause or aggravate visual fatigue and to suggest how adequate attention to ergonomics can largely overcome the problem. 11.2.14 (78088)
Glenvflle, M., and Wilkinson, R.T. Portable devices for measuring performance in the field: The effects of sleep deprivation and night shift on the performance of computer operators. Ergonomics, Aug 1979, 22.8, 9 2 7 - 9 3 3 . The performance of 12 computer operators was measured in the field on two new portable tests of reaction time, during the first night of the night shift at 0400 h and at the beginning of the day shift (0800 h), over three successive three-week comparisons. The results were: (i) mean reaction time increased significantly on the night shift as compared with the day; (ii) the adverse effect of the night shift was absent during the first comparison and became increasingly apparent on the second and third replications. These results: (i) provide evidence of inferior performance on the night as compared with the day shift in the field; (ii) show that data from previous studies of sleep deprivation in the laboratory are able to provide a good indication of what was to be expected in the field; (iii) emphasise the need for
Oleinikov, V.A. Physiological aspects of the work of miners on working faces. Human Physiology, Sep/Oct 1978, 4 . 5 , 6 7 7 683. Working conditions in the coal industry differ in many important respects from those in other branches of the national economy; underground working, the danger factor, greater physical and neuropsychic loads. The widespread introduction of mechanisation in one of the main areas of mining, namely on the working face, has been aimed at making the work easier and increasing its productivity. Mechanised systems of the KM-87 type are most widely used in mines in the Donetsk coalfield. Walls equipped with these systems account for about 90% of the total amount of coal won from mechanised wails. However, problems of work physiology in highly mechanised working faces in coal mines have been inadequately studied and it is the purpose of this article to examine some of the features which distinguish the work of miners. Observations were made on 140 miners working on four working faces ('Voroshilovgradugol' and 'Donbassantratsit') equipped with mechanised systems of the KM-87 type. The working faces studied had a daily coal output of 600 to 2200 tons. 11.2.16 (78127)
Dorling, E. Physiological analysis of work with fork lift trucks (Arbeitsphysiologische Analysen zum Thema Gabelstapler). (In German.) Tu Jul/Aug 1978, 1 9 . 7 - 8 , 2 5 2 - 2 5 7 . Abstr in: CIS Abstracts (CIS 79-1177). Measurement methods used were pulse-rate and ECG, oxygen intake and energy expenditure, reaction time, visual flicker fusion threshold, mechanical vibration. These measurements enabled the author to evaluate the influence on the human body of power steering, a lifting mast offering a free field of vision, an adjustable steering column, more leg room and various models of drivers' seats. It appears that power steering and a hydraulically suspended driver's seat gives a higher safety factor and improves working conditions.
Applied Ergonomics
June 1980
107