Video Display Terminal Operators Research Articles

観葉梅物を見ることがＶＤＴ作業に伴う視覚疲労に及ぼす影響

In this study, three experiments were performed in order to investigate the effect of ornamental foliage plants on visual fatigue caused by visual display terminal operation. Visual fatigue was evaluated as critical flicker fusion frequency (CFF). Four students served as subjects in each experiment.The experiment (1) was carried out to examine the reduction of visual fatigue by viewing plants during visual display terminal operation. As the results, the CFF of the subjects in case of viewing plants was higher than that in case of viewing no plant. Especially, the difference of the CFF of the subject A was 9.3%.The experiment (2) was carried out to examine the recovery of visual fatigue by viewing plants after visual display terminal operation. As the results, the CFF of the three subjects except A increased in case of viewing plants and decreased in case of viewing no plant. The differences of the CFF of the subjects B and D were 4.6% and 3.6% respectively.The experiment (3) was carried out to determine whether difference in kinds of plants could bring about difference of the recovery of visual fatigue. As the results, average of the CFF of the subjects in case of viewing Schefflera arboricola “Hong Kong”, Cupressus macrocarpa “Gold Crest” and no plant decreased by 2.7%, 3.1% and 6.0% respectively, while average of the CFF of the subjects in case of viewing Dracaena fragrans “Massangeana” showed an increase of 0.6%.

Epidemiological studies of work with video display terminals and adverse pregnancy outcomes (1984-1992).

Many epidemiological studies have investigated the claim that work with video display terminals (VDT) is a risk factor during pregnancy. Results have been inconsistent, although in the majority of cases the hypothesis was not supported. Exposure assessment has been very poor and the statistical power of the studies generally low. Overall, the studies indicate that VDT operators are not at greater risk than the general population, because very low frequency (VLF) magnetic fields do not appear to be a risk factor and extremely low frequency (ELF) magnetic field exposure is not significantly greater than that experienced in other occupational and residential environments. However, since some studies lend support to the hypothesis that ELF magnetic fields may be a risk factor for pregnancy outcome, studies of subjects exposed to higher than average ELF fields are justified.

Ergonomics in the Laboratory Environment

The focus of this report is how ergonomics--the art of making equipment fit the user--is applied to video display terminal (VDT) use in order to improve productivity. It is recommended that VDT operators be made more comfortable by using ergonomic chairs and tables. The placement of computer screens and keyboards at the workstations should be tailored to the body and its natural motion in order to decrease physical stress.

Visual comfort in using different VDT screens

In order to meet the goal of user comfort of information displays, visual problems of video display terminal (VDT) work were studied through the analysis of visual functions in two experiments. Eye movement analysis, in Experiment 1, revealed that VDT operators had to move their eyes 2.5 times faster than traditional clerical workers. Lens accommodation, pupil size, and subjective visual comfort were investigated in Experiment 2. A significant correlation was found between the velocity of lens accommodation and the subjective visual comfort while viewing seven different displays (r = .809). A positive‐type cathode‐ray tube (CRT), which has dark characters on a light background, was ascertained to be the most appropriate display type, while working with a liquid crystal display (LCD) was considered to be the least visually comfortable, with the lowest accommodative velocity.

A survey of electric and magnetic fields among VDT operators in offices

The ambient electric and magnetic fields as well as the electromagnetic fields associated with video display terminals (VDTs) at 150 offices are measured. The aim of the study is to determine the general level of the various electromagnetic parameters in offices and establish a technical base for a case referent study of skin symptoms among VDT workers. The median value of the 50-Hz background field in the 150 offices is 0.07 mu T. Seven of the offices have background levels higher than 0.5 mu T, which is high enough to cause distortion of the picture on the screen. The dominant source for electric fields in the ELF range is electric equipment in the office, not the VDTs. The equivalent surface potential is less than 0.5 kV for 63% of the measured VDTs. The computer monitor is a major source of magnetic fields in the offices. The median value of the magnetic field in the ELF range in front of the VDT is 0.21 mu T, and in the VLF range it is 0.03 mu T.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

VDTs

As the use of video display terminals (VDTs) has expanded, questions have been raised as to whether working at a VDT affects the risk of adverse pregnancy outcome. A particular focus for these questions has been the very low frequency (VLF) magnetic field produced by a VDT's horizontal deflection coil. VDTs also produce VLF electric fields, extremely low frequency (ELF) electric and magnetic fields, and static electric fields, Ten studies of pregnancy outcome in VDT operators have been conducted in six countries, and with one exception, none has concluded that magnetic fields from VDTs may predispose pregnant operators to spontaneous abortion or congenital malformation. The epidemiologic studies conducted thus far do not provide a basis for concluding that VDT work and adverse pregnancy outcome are associated. Studies of fetal resorptions and malformations in rodents exposed to VLF magnetic fields have produced inconsistent findings. Two laboratories in Sweden that studied mice have reported positive results, one laboratory showing field-related malformations (but not resorptions) and the other showing field-related resorptions (but not malformations). Two Canadian laboratories have reported negative results in rats and mice. Studies of avian embryos have also yielded inconsistent results, but lacking a maternal-fetal placental interface, avian embryos are a questionable model for evaluating human reproductive risks. Finally, VLF electric and magnetic fields measured at the operator position are in compliance with field strength standards and guidelines that have been established around the world.

Video Display Terminal Health Concerns

The growing population of video display terminal (VDT) operators in today's computerized workplace has led to an increased incidence of common office health problems. The most common of these problems include visual, musculoskeletal, and stress related complaints. The well informed occupational health nurse understands that it is the nature of the work and work environment, not the VDT, which presents health risks to operators. Therefore, the problems can be greatly prevented through proper work station ergonomics and well designed jobs. Education regarding the significance of these issues becomes a key form of intervention. This effort must be directed toward management as well as VDT operators.

Measurements of extremely low-frequency magnetic fields around video display terminals.

The extremely low-frequency (ELF) magnetic field emissions of seven video display terminal (VDT) models were measured. A measuring coil with a linearized frequency response (50 Hz to 25 kHz) was used. The dominating ELF magnetic field around the terminals was the 50 or 60 Hz asymmetric triangular waveform from the vertical deflection coil of the cathode ray tube. At the distance of 50 cm, the magnetic field strength was still slightly higher than the background level in usual office rooms, but several orders of magnitude lower than the thresholds of known interaction mechanisms. Some recent experiments suggest that certain biological effects may occur at field strengths only a few times higher than those found at the position of VDT operators, but the significance of these effects to human health is not known.

Work with video display terminals among office employees. IV. Refraction, accommodation, convergence and binocular vision.

The present study is the fourth of a major epidemiologic health investigation on work with a video display terminal (VDT). The other studies showed that VDT operators replying to questionnaires have more eye discomfort than a reference group of office employees not employed in VDT work and that women have more eye discomfort, musculoskeletal complaints, headache, and skin disorders than men. Routine ophthalmologic examinations failed to establish any appreciable differences between the groups; for example, the prevalence of myopia was the same. In the present study, the VDT operators and referents were examined before and at the end of work sessions for changes in refraction, accommodation, convergence capacity, and binocular vision such as heterophoria and fusion range. No differences could be established between the VDT operators and the referents.

Work with video display terminals among office employees. V. Dermatologic factors.

According to some reports, mainly from Norway, work with a video display terminal (VDT) has been suspected to cause skin rashes. In conjunction with an epidemiologic study of some 550 office employees, 74 persons, who complained of skin symptoms, were examined by occupational dermatologists. The objective was to see whether the findings from earlier reports could be confirmed, whether any type of rash could be suspected to depend on VDT work, and whether positive findings might be explained by means of physical data. Many different diagnoses were made, but no case demonstrated the clinical picture described among VDT operators from Norway. Subjects with seborrheic dermatitis, acne, and rosacea were overrepresented in the exposed group. Whether this occurrence was due to physical factors, psychological factors, or pure chance is still unclear. This study and observations from our clinic imply that a relationship might exist between VDT work and aggravation of seborrheic dermatitis, acne, and rosacea and probably poikiloderma of Civatte.

Work with video display terminals among office employees. III. Ophthalmologic factors.

The present ophthalmologic study is the third part of a major epidemiologic health investigation on work with a video display terminal (VDT). An initial study showed that VDT operators replying to a questionnaire reported more eye discomfort than a reference group not employed in VDT work and that women reported more eye discomfort, musculoskeletal discomfort, headache, and skin disorders than men, irrespective of whether or not they were employed in VDT work. In the present study the ophthalmologic history of eye diseases and eye discomfort yielded a much lower percentage response for symptoms and discomfort than the questionnaire, and, just as with visual acuity and refraction, there was no difference between the exposed and reference groups or between the men and women. The exposed subjects were found to be overcorrected in terms of presbyopia addition in relation to work distance. As regards ocular examination findings, low frequency rates were noted for pathological lens opacities. Opacities of this kind were slightly more frequent among the VDT operators than among the referents, but the difference was not statistically significant. There were no other differences in the ocular findings of the exposed and reference groups.

Work with video display terminals among office employees. II. Physical exposure factors.

This is the second report in a major epidemiologic health investigation on work with a video display terminal (VDT). The first study showed that VDT operators reported more eye discomfort than a reference group not employed in VDT work and that women reported more eye discomfort, musculoskeletal complaints, headache, and skin disorders than men, regardless of whether they worked with a VDT or not. The present report contains the results of the occupational hygiene measurements (indoor climate, lighting and electrostatic conditions). Considerable differences were found between VDT operators and referents and also between sexes. Indications were obtained of a possible relationship between eye discomfort and luminance ratios in the working field of vision. Otherwise, no association could be established between occupational exposure factors and subjective eye discomfort, musculoskeletal complaints, headache, or skin disorders.

Work with video display terminals among office employees. I. Subjective symptoms and discomfort.

Subjective symptoms and discomfort were evaluated by means of a questionnaire and compared between approximately 400 video display terminal (VDT) operators and 150 selected referents. Previous and current illnesses, educational status, and smoking and drinking habits were also studied. The results showed the VDT operators to have more eye discomfort and possibly also more musculoskeletal discomfort in the shoulders, neck, and back than the referents. The VDT group also reported more skin disorders. In addition, women reported consistently more disorders than men, regardless of whether or not they were employed in VDT work. Women in general displayed greater morbidity than men. Eye discomfort, musculoskeletal discomfort, headache, and skin disorders were found to be significantly correlated in the material. The results also indicated that total daily workhours and time spent looking at the VDT screen were related to the degree of discomfort. Even when the subjects were divided into subgroups with reference to the various enterprises, the types of work and the makes of VDT, the differences obtained in the degree of discomfort appeared to be due to variations in the length of workhours.

An Alternative to Reduce the Physical Stress of VDT Operators

A Study has been conducted to compare the effectiveness between improvement of furniture design (ergonomic design) and physical exercise in reducing musculoskeletal stress of the VDT (Video Display Terminal) operators. As an objective measurement, electromyograms (EMG) were measured from the neck, the left and right trapezius, L2/L3 region of back, triceps, flexor carp radialis and extensor carpi ulnaris. Subiective questionnaires were also used. Each of the five subjects was tested for two days (8 hours/day) in two different work stations which are an ergonomically designed work station and a traditionally designed work station using non-ergonomic devices. It was found that the physical exercises could reduce musculoskeletal stress as effectively as the ergonomic design.

Video Display Terminals: Radiation Issues

During the past decade, the use of video display terminals (VDTs) in information processing and related applications has grown exponentially. Recent estimates place the number of terminals in the workplace at more than ten million. Along with this rapid growth there has been a concomitant increase in concern about the radiation emissions from the VDT. Several types of radiation can be emitted by the terminal. Cataracts, reproductive problems, and skin rashes have been reported by VDT operators and are alleged to result from radiation exposure. However, measurements of the radiation emissions, when compared to the present occupational exposure standards, lead to the conclusion that the terminal does not present a radiation hazard to the VDT operator.

The Physical, Mental, and Emotional Stress Effects of VDT Work

Muscular aches and pains are among the major complaints voiced by video display terminal (VDT) operators. In studies from Europe and the United States large percentages (over 50%) of VDT operators report back pain, sore shoulders, and stiff and sore necks. The type of VDT job task influences the level of complaints, with clerical VDT operators reporting higher levels than professional VDT users. The application of ergonomics to reduce muscular loads should benefit VDT operators. Suggestions for workstation design and administrative controls are presented.

Display station anthropometrics: preferred height and angle settings of CRT and keyboard.

This study investigates display station physical adjustments preferred by a sample of visual display terminal operators. Participants in the study were selected to assure representation of extremely short and extremely tall persons, as well as persons of midrange physical stature. Individual operators were led through a step-by-step sequence to determine their preferred initial settings of seat height, keyboard height and slope angle, and CRT height and tilt angle. Each operator then performed a brief text input task, after which final preferred adjustments were measured. Intermeasure correlation strongly suggest that “flat” (low slope angle) keyboards are inappropriate for short operators who select low seat heights. In addition, the keyboard angle adjustments preferred by most operators substantially exceed a current German ergonomic display station requirement.

An investigation of health complaints and job stress in video display operations.

A questionnaire survey dealing with working conditions, job stress factors, health complaints, and psychological mood state was filled out by approximately 250 video display terminal (VDT) operators and 150 nonoperator control subjects at five participating work sites. Clerical VDT operators reported higher levels of job stress and health complaints but little difference in psychological mood state than did professional VDT operators and the control subjects. The job stressors showing the greatest impact on the clerical operators dealt with workload, workpace, lack of control over job activities, boredom, and concerns about career development. The health complaints that showed the greatest differences between the groups dealt with visual, musculoskeletal, and emotional health problems. The results indicate that job content factors and VDT use interact to contribute to VDT operator problems.