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Physical discomfort among visual display terminal users in a semiconductor manufacturing company: a study of prevalence and relation to psychosocial and physical/ergonomic factors.

The associations among several alleged psychosocial and physical/ergonomics risk factors and the visual and musculoskeletal discomforts were assessed in a cross-sectional study of 119 video display terminal (VDT) users in a semiconductor manufacturing company. Cases of discomfort were identified using self-reported discomfort symptoms through questionnaire surveys. Data on individual, physical/ergonomic, and psychosocial aspects were obtained. Multivariate logistic regression models were developed to predict physical discomforts of 11 body areas. The prevalence of upper extremity discomfort found in this semiconductor manufacturing company was 42%, which is similar to the prevalence among VDT users in telecommunication companies and the newspaper industry. Full-time VDT users (data-entry personnel, programming engineers, and CAD engineers) had significantly higher rates of physical discomfort (66%) than part-time VDT users (fabrication engineers) (41%). Physical/ergonomic variables were found more dominant than psychosocial factors for visual and upper extremity discomforts. However, psychosocial variables were the dominant for back and lower extremity discomfort, when compared with the subjectively characterized physical/ergonomic factors. Because both physical/ergonomics variables and psychosocial factors and some of their interactions were associated with visual and musculoskeletal discomfort, integrating psychosocial prevention with physical/ergonomic design improvements is an effective approach to reducing the prevalence of discomfort.

Adult↗

PubMed2000

Effects of word spacing on reading Chinese text from a video display terminal.

This study investigated the effects of designing space between words in Chinese text, i.e., whether using a "word" instead of a "character" as a presentation unit, will facilitate the performance of reading from a video display terminal. Experimental results indicated that the main effect of word spacing significantly affected the reading time and the number of questions answered correctly. Subjects spent less time on the text with half-character word spacing or with whole-character word spacing than with conventional type (without word spacing). We also discovered that the number of questions answered correctly for stimuli with half-character spacing is significantly greater than that for stimuli with whole-character spacing, while both are smaller than for stimuli with conventional type. The additional variables, such as text difficulty and display control have significant effects as well. Our results suggested that the optimal word spacing in Chinese text should be greater than that in the traditional layout and less than a whole-character spacing. Apparently, in Chinese text, using a "word" as a presentation unit is more favorable than the traditional layouts that do not have any explicit word boundaries. The word spacing design may benefit in reading difficult or unfamiliar materials and further apply in emergency situations or in reading ambiguous sentences.

Adult↗

PubMed2001

Psychological factors and visual fatigue in working with video display terminals.

OBJECTIVES: To examine the part played by psychological factors in complaints about visual health reported by banking officers who work at video display terminals (VDTs). METHODS: Out of a population of 385 bank workers, a group of 212 subjects without organic visual disturbances (as determined by ophthalmological examination) who share a work environment and job duties was selected. Three questionnaires were administered to these subjects: (a) the NIOSH job stress questionnaire; (b) a questionnaire investigating subjective discomfort related to environmental and lighting conditions of the workplace; (c) a questionnaire on the existence of oculovisual disturbances. Correlation and multiple regression analyses were performed to examine for the presence of predictors of asthenopia. RESULTS: Social support, group conflict, self esteem, work satisfaction, and underuse of skills were found to be predictors of visual complaints; social support played a part also as a moderating factor in the stress and strain model; this model accounted for 30% of the variance. Subjective environmental factors, although in some cases significantly correlated with asthenopia, were not found to be strong predictors of the symptoms. CONCLUSIONS: Some part of the complaints about visual health reported by VDT workers are likely indirect expressions of psychological discomfort related to working conditions.

Adult↗

PubMed1990

Use of video display terminals during pregnancy and the risk of spontaneous abortion, low birthweight, or intrauterine growth retardation.

Use of video display terminals (VDTs) during pregnancy among working women was examined using data from a large case-control study of spontaneous abortions (SAB) occurring in 1986-1987. The crude odds ratio for SAB and VDT use was 1.2 for use of less than 20 hours per week (95% CI = 0.88, 1.6) as well as for 20 hours or more (CI = 0.87, 1.5), with little change after adjustment for a variety of confounders. The effects of VDT use may vary by the gestational age at SAB, with stronger associations seen in earlier (less than or equal to 12 weeks) compared to later SABs. Use of VDTs within specific occupational categories was examined, yielding adjusted odds ratios varying from 0.5 to 1.7. The risk for low birthweight (LBW) among the control group also was not greatly elevated at either VDT use level, with adjusted ORs of 1.1 (0.52, 2.1) and 1.4 (0.75, 2.5), respectively. However, the risk for intrauterine growth retardation was somewhat elevated among women with greater VDT use (OR = 1.6, CI = 0.92, 2.9).

Abortion, Spontaneous↗

PubMed2002

Office workers and video display terminals: physical, psychological and ergonomic factors.

The purpose of the pilot study was to examine the psychological and physical symptoms reported by video display terminal (VDT) and non-VDT users in relation to intensity and duration of VDT exposure, ergonomic characteristics of the work station, workers' perceptions of the working environments, medical conditions, job satisfaction, and mood states. Thirty VDT users and 16 non VDT users were selected from four departments of a major radiopharmaceutical company for participation in the cross-sectional study. Self-administered questionnaires were utilized to obtain information on symptoms, medical conditions, job satisfaction, mood states, and the working environments. Objective measurements were obtained to provide information on the various ergonomic components of the work station. The study corroborated findings reported in previous studies, whereby eye related symptoms were associated with VDT usage. A higher percentage of symptoms were reported among VDT users even when they had more control over their work stations. These workers expressed higher levels of job satisfaction, and lower levels of tension, fatigue, confusion, anger, and depression than non-VDT users. Most importantly, a trend in symptomatology was identified, whereby symptoms appeared to increase as duration of VDT exposure increased.

Adult↗

PubMed1997

Prescribing for the moderate-to-advanced ametropic presbyopic VDT user. A comparison of the Technica Progressive and Datalite CRT trifocal.

BACKGROUND: Use of video display terminals (VDTs) is expected to dramatically increase. This clinical study was performed to examine the moderate-to-advanced ametropic presbyopic VDT user to determine the most prevalent visual or physical symptoms incurred while working at a VDT, and to develop a comparative benefit analysis of two currently available occupational lens designs. METHODS: Twenty-four symptomatic VDT users who were currently wearing a non-occupational lens design were selected from a pool of 100 applicants. The non-occupational lens distribution included 17 bifocals, 3 trifocals and 4 progressives lenses. The subjects compared two occupational lens designs. RESULTS: Statistical analyses indicated that the frequency and severity of seven of 10 symptoms reported were significantly reduced by wearing the occupational lenses, including the three most frequently reported pre-existing symptoms of neck/shoulder aches, eyestrain, and blurred intermediate vision. CONCLUSION: Study results suggest that symptomatic moderate-to-advanced ametropic presbyopic VDT users may benefit from an occupational progressive lens when work involves prolonged or exclusive viewing of a VDT screen. An occupational trifocal may benefit VDT users also required to perform other viewing tasks.

Aged↗

PubMed1994

Investigation of a spontaneous abortion cluster: lessons learned.

An investigation of a reported spontaneous abortion excess in an office environment was undertaken employing a multidisciplinary approach, including (1) an epidemiologic/validation step; (2) an industrial hygiene survey, including electromagnetic field measurements and indoor air quality determinations; and (3) a risk perception/risk communication component. This approach was needed because there are numerous chemical and physical agents and psychosocial stressors that may potentially impact the reproductive status of female office workers. Although video display terminals (VDTs) are typically the focus of spontaneous abortion (SAB) investigations, one cannot ignore other stressors in the environment. Magnetic field exposures within a payroll area were determined using a hand-held survey meter and data logging dosimeter. On average, the full shift time-weighted average exposures of workers to extremely low frequency (ELF) magnetic fields in the payroll office area ranged from 1.0 to 5.6 mG. Influencing the investigation's protocol design were the Centers for Disease Control's (CDC's) recent Guidelines for Investigating Clusters of Health Events. Although these guidelines grew primarily out of cancer cluster investigations, we applied them in this instance and found them to be generalizable to reproductive hazards investigations. A spontaneous abortion excess was validated over a 2-year period among 26 women with 32 reproductive events, with rates 1.5-2.5 times the expected, depending on comparison figures used. Lessons learned in the investigation, including the applicability of the CDC's Cluster Investigation Protocol and the enormous importance of risk perception and risk communication, are described.

Abortion, Spontaneous↗

PubMed1997

The psychosocial work environment and skin symptoms among visual display terminal workers: a case referent study.

BACKGROUND: This study is a part of the interdisciplinary project The Office Illness Project in Northern Sweden, which was initiated with a questionnaire study in late 1988. Previously published results from the project have shown that facial skin symptoms reported among visual display terminal (VDT) workers are associated with a number of exogenous factors. This part of the project investigated the relation between the psychosocial work environment and facial skin complaints. METHODS: From an initial questionnaire study among 4943 office workers, 163 VDT workers were selected for a case referent study of facial skin symptoms. The data comprise a self-administered questionnaire filled out by 149 subjects and interviews with representatives of the organizations concerned. RESULTS: Psychosocial conditions, especially lack of social support from co-workers, were associated with an increased risk of reporting skin symptoms. Stratification by sex showed that the associations between some psychosocial factors and health differed between men and women. The results indicate that there might be an interaction between psychosocial factors and electric fields in the workplace which increases the risk of reporting skin symptoms. CONCLUSIONS: This study supports the idea that the aetiological basis of facial skin symptoms among VDT-workers includes physical as well as psychosocial factors, and that the interaction between such factors might be significant in the understanding of skin complaints among VDT workers.

Adult↗

PubMed1991

Skin problems in users of video display terminals. Discrepancy between subjective symptoms and objective signs.

The skin has become a target organ for concerns related to work with video display units (VDU). The aim of this investigation was to describe the clinical picture, to investigate whether skin problems are more common in VDU-exposed persons than in non-exposed controls, whether there are differences in objective and/or subjective symptoms and signs, and whether there is a "specific" dermatosis associated with VDU work. A self-reported questionnaire was mailed to 3,877 individuals. One out of five questions concerned the presence of skin problems. Of this group, 809 underwent a clinical dermatological evaluation in addition to filling out a structured questionnaire. Self-reported skin symptoms increased with increasing exposure to the VDU. The clinical diagnosis, based on objective signs and anamnestic data showed a somewhat attenuated association with exposure. The status diagnosis, based solely on objective signs, failed to show any association to VDU exposure. Unilateral skin rashes occurred at the same frequency in the exposed and the non-exposed groups. It is concluded that there is nothing in this investigation, or in any other investigation, that would speak against the notion that VDU-related skin problems and the allergy to electricity is just another facet of the "20th century syndrome". It is possible that individuals suffering from this condition, are conditioned to respond to certain stimuli by neurogenic release of mediators.

Computer Terminals↗

PubMed2002

Frame of reference and adaptation to directional bias in a video-controlled reaching task.

The present study (N=56) investigated spatio-temporal accuracy of horizontal reaching movements controlled visually through a vertical video monitor. Direct vision of the hand was precluded and the direction of hand trajectory, as perceived on the video screen, was varied by changing the angle of the camera. The orientation of the visual scene displayed on the fronto-parallel plane was thus congruent (0 degrees condition) or non-congruent (directional bias of 15 degrees, 30 degrees or 45 degrees counterclockwise) according to the horizontal working space. The goal of this study was to determine whether local learning of a directional bias can be transferred to other locations in the working space, but taking into account the magnitude of the directional bias (15 degrees, 30 degrees or 45 degrees ), and the position of the successive objectives (targets at different distances (TDD) or different azimuths (TDA)). Analysis of the spatial accuracy of pointing movements showed that when introducing a directional bias, terminal angular error was linearly related to the amount of angular perturbation (around 30%). Seven trials were, on average, necessary to eliminate this terminal error, whatever the magnitude of the directional bias and the position of the successive targets. When changing the location of the spatial objective, transfer of adaptation was achieved in the TDD condition but remained partial in the TDA condition. Furthermore, initial orientation of the trajectory suggested that some participants used a hand-centred frame of reference whereas others used an external one to specify movement vector. The adaptation process differed as a function of the frame of reference used, but only in the TDA condition. Adaptation for participants using a hand-centred frame of reference was more concerned with changes in the shape of the trajectory, whereas participants using an external frame of reference adapted their movement by up-dating the initial direction of hand trajectory. As a whole, these findings suggest that the processes involved in remote visual control of hand movement are complex with the result that tasks requiring video-controlled manipulation like video-controlled surgery require specific spatial abilities in actors and consequential plasticity of their visuo-motor system, in particular concerning the selection of the frame of reference for action.

Adaptation, Physiological↗

PubMed1999

Luminance of the surround and visual fatigue of VDT operators.

Luminance distribution in the visual field is considered as one of causal factors with a significant influence on visual fatigue, especially for intensive and extended Video Display Terminal (VDT) work. The aim of the study was to define visual fatigue of VDT operators for different values of surrounding luminance. Experiments were carried out in laboratory conditions under 3 lighting conditions. Only 1 lighting parameter--the luminance of the wall behind the display (surrounding luminance)--changed. Visual fatigue was measured both by a subjective evaluation of different visual complaints (asthenopic symptoms) and by objective measurements of changes in the following visual functions: accommodation, convergence, habitual horizontal phoria, critical fusional frequency (CFF), and visual acuity. The same experiments were done for CRT (Cathode Ray Tube) and LCD TFT (Liquid Crystal Display with Thin Film Transistor) screens. The results of the study have shown that there was no significant influence of the value of surrounding luminance on the asthenopic symptoms for either type of screen. A general tendency towards bigger visual complaints for LCD TFT than for CRT participants was found. An objective evaluation of visual fatigue demonstrated a tendency towards bigger changes in visual functions with an increase of surrounding luminance for both screens. Statistical analysis of the results has shown that surrounding luminance influences significantly the reduction of the accommodation amplitude (significance level <.05).

Adolescent↗

PubMed1997

High refresh rate and oculomotor adaptation facilitate reading from video displays.

Reading from a video display terminal (VDT) was tested at screen refresh rates of 500 Hz and 60 Hz. Reading was initially 8 words/min (3.05%) faster at 500 Hz. A hypothesis that reading rate on VDTs is limited by stimulus availability accounts for the difference. When the eye reaches a new fixation position, it 'parks' until a sample of text appears at the fovea. Then processing resumes in the normal way. This idea, combined with the 500-Hz reading data, can predict reading rate at any refresh rate, and is quantitatively confirmed by the reading rate at 60 Hz. The difference in reading rates disappeared for the second half of the text, as a result of differences between frequencies of eye movements in the two refresh conditions. From the first half to the second, subjects at 60 Hz made more large forward saccades and fewer small reverse saccades. Both changes make sampling of the text more sparse, compensating for the dead time between samples. Subjects were unaware of refresh conditions, differences in their reading rates, and types of eye movements they generated. Reading from a continuously illuminated active-matrix display is slightly faster than from a comparable VDT.

Adaptation, Ocular↗

PubMed2002

Medical and social prognosis for patients with perceived hypersensitivity to electricity and skin symptoms related to the use of visual display terminals.

OBJECTIVES: This study attempted to give a medical and social prognosis for patients with perceived "electrical sensitivity". METHODS: In 1980-1998, 350 patients with electrical sensitivity were registered at the University Hospital of Northern Sweden in Umeå, Sweden. Those with hypersensitivity to electricity had multiple symptoms evoked by exposure to different electric environments. Those with skin symptoms related to the use of visual display terminals (VDT) predominantly had facial skin symptoms evoked by a VDT, television screens, or fluorescent light tubes. A questionnaire on civil status, current health status, care, treatment and other measures taken, consequences of the problem, eliciting factors, and current employment was sent to all the patients. The response rate was 73%. Of the 50 respondents with hypersensitivity to electricity, 38% were men and 62% were women. Of the 200 patients with skin symptoms related to VDT use, 21.5% were men and 78.5% women. RESULTS: More women than men had turned to caregivers, including complementary therapies. A larger proportion of patients with hypersensitivity to electricity (38%) than those with skin symptoms related to VDT use (17%) was no longer gainfully employed. Both groups reported a higher symptom frequency than that reported by the the general population. Over time, the medical prognosis improved in the latter group but not in the former. CONCLUSIONS: Patients with hypersensitivity to electricity, particularly women, have extensive medical problems and a considerable number of them stop working. Many patients with skin symptoms related to VDT use have a favorable prognosis. Both groups need early and consistent management.

Activities of Daily Living↗

PubMed1995

Video display terminal very low frequency measurements: the need for protocols in assessing VDT user "dose".

It has been well established that video display terminals (VDTs) which employ the use of a cathode ray tube produce electric and magnetic fields of varying frequencies. Numerous studies have attempted to relate magnetic field exposure from VDTs in the extremely low frequency (ELF) and very low frequency (VLF) bands to adverse pregnancy outcome. Initial studies utilized VDT use time as a surrogate assessment of exposure, while later studies have obtained actual measurements. These measurements have been typically obtained at fixed distances from the screen. While VDT measurement criteria have been established for measuring VDT fields, criteria for the assessment of VDT user exposure has not. VLF magnetic and electric field measurements from approximately 140 and 40 different VDTs, respectively, were obtained over a 3-y period at the following positions: 0.50 m from the vertical centerline of the screen and at the approximate location of VDT user reproductive organs--0.30 m above the seat of the VDT operator in the working position. The measurement results of the two aforementioned locations were compared and demonstrate very little correlation. This lack of correlation indicates that VDT operator exposure assessment criteria are needed to determine any dose-response relationship between VDT electric and/or magnetic fields and adverse health implications.

Abortion, Spontaneous↗

PubMed1998

Effects of gestational exposure to a video display terminal-like magnetic field (20-kHz) on CBA/S mice.

Possible adverse effects of magnetic fields (MFs) on reproduction have been an open question. To verify the embryo-lethal effect of pulsed MF of the type emitted by video display terminals (VDTs) reported previously in CBA/S mice, a developmental toxicity study was conducted in animals of the same origin. Mated CBA/S mice (80-86 pregnant animals per group) were exposed to a 20-kHz MF with sawtooth waveform continuously from gestational day 0-18. The flux density of the vertical MF was 15 microT peak-to-peak (150 mG). This field was previously reported to increase the number of resorptions in CBA/S mice. On gestational day 18, the dams were killed and blood and bone marrow samples were taken for hematology and micronuclei analysis, respectively. The number of corpora lutea was counted and the content of the uterus examined. There were no statistically significant differences in maternal or fetal body weights, number of corpora lutea, implantations, resorptions, dead and live fetuses, or external and skeletal malformations. MF did not alter the number of blood cells or cause micronuclei in bone marrow erythrocytes in the dams. The mean number of resorptions was slightly but not statistically significantly, higher in the MF group than in controls. The results do not indicate marked developmental, hematological, or clastogenic effects of 20-kHz MFs.

Abnormalities, Radiation-Induced↗

PubMed2001

Consideration of three types of spontaneous eyeblink activity in normal humans: during reading and video display terminal use, in primary gaze, and while in conversation.

PURPOSE: To consider the conditions under which the so-called spontaneous (endogenous) eyeblink activity has been assessed by different investigators over the last 75 years and to consider the most appropriate terminology. The reason for this analysis was to try to identify why such different values for the spontaneous eyeblink rate (SEBR) have been reported. METHODS: A retrospective evaluation of published articles was carried out to identify whether the SEBR assessments were consistently dependent on the activity of the subjects while spontaneous eyeblink activity was being investigated. These were compared with assessments of SEBR in young adult subjects under equivalent conditions. RESULTS: Assessments of spontaneous eyeblink activity revealed that SEBR in a reading posture is lower than that in primary gaze, and SEBR is higher when subjects are in conversation. Such differences are also generally found in literature reports, especially if the primary gaze assessment is carried in silence. Electrophysiological measures of SEBR yield slightly higher values compared with observational techniques. Statistical analysis (with calculation of 95% confidence interval values) indicate that reading-SEBR should be between 1.4 and 14.4 eyeblinks/min, primary gaze-SEBR between 8.0 and 21.0 eyeblinks/min and conversational-SEBR between 10.5 and 32.5 eyeblinks/min for normal adults. CONCLUSIONS: It is inappropriate to simply state a value for spontaneous eyeblink rate because it is so dependent on experimental conditions. It is further proposed that reports of SEBR measures should be prefixed by these experimental conditions, namely reading-SEBR, primary gaze-SEBR (in silence) and conversational-SEBR.

Adult↗

PubMed1996

Subclinical impairment in the median nerve across the carpal tunnel among female VDT operators.

Sensory nerve conduction velocities in the palm-to-finger (SCV-pf), wrist-to-finger (SCV-wf), wrist-to-palm (SCV-wp), and wrist-to-elbow (SCV-we) segments and the distribution of nerve conduction velocities in the right median nerve were determined among 27 female operators aged 19-37 and 19 healthy women (controls) aged 19-31 to estimate the prevalence of subclinical carpal tunnel syndrome (CTS). Also, the WF/PF ratio, dividing the SCV-wf by the SCV-pf, was calculated to assess abnormalities of nerve conduction within the carpal tunnel. The operators were engaged in data entry in front of a visual display terminal (VDT) for about 6 h/day, and their working duration was between 1 and 17 (mean 6) years. The SCV-wf, SCV-wp, and WF/PF ratio in the operators were significantly lower than those in the controls. The rate of persons with the WF/PF ratio of less than 90%, i.e., below normal limits in the 19 controls, was significantly higher in the operator group (37%) than in the control group (0%). The operators complained of more symptoms related to CTS than did the controls, but any symptoms were not associated with slowing of nerve conduction velocities in the operators. In the controls, the WF/PF ratio was not closely correlated with skin temperature or age despite the presence of significant relations between skin temperature and the SCV-wf, SCV-pf, and SCV-wp; the interpersonal variability of the WF/PF ratio was much smaller than that of all SCVs. In the light of the present and previous studies, the rate of VDT operators with subclinical CTS seems to be high, independent of its symptoms. Also, the WF/PF ratio will be a useful and reliable screening method for the early detection of CTS due to repetitive wrist and finger movements involved in work.

Adult↗

PubMed1997

Facial skin symptoms in office workers. A five-year follow-up study.

This longitudinal study is a part of the interdisciplinary project. The Office Illness Project in Northern Sweden, which was initiated with a questionnaire study in late 1988. Among 3233 visual display terminal (VDT) workers, an initial case-referent group of 163 individuals was selected. The data acquisition included two questionnaires, assessments at the workplaces, interviews with personnel staff of the organizations concerned, and a clinical examination of the respondents. Subjects participating in the case-referent study 1988 filled out a questionnaire in the beginning of 1994. The primary objective of this study is to discuss changes in and causes of facial skin symptoms among VDT workers in the long term. The results show that (1) facial skin symptoms among VDT workers seem to be of a transitory nature for most of those with isolated skin symptoms, whereas the prognosis for those with a more complex symptom picture is more negative, (2) assumptions that measures taken in the work environment-including those involving the VDT and other electric devices-would have a positive effect on symptoms were not supported, and (3) the strongest external risk indicators for lasting skin symptoms seem to be found in the psychosocial work environment. Therefore, one important issue for the understanding of facial skin symptoms is organizational climate and personnel policies. The results also imply that individual factors, both constitutional and psychological, must be considered.

Adult↗