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PubMed2003

[Influence of different lighting levels at workstations with video display terminals on operators' work efficiency].

The aim of this work was to evaluate the influence of different lighting levels at workstations with video display terminals (VDTs) on the course of the operators' visual work, and to determine the optimal levels of lighting at VDT workstations. For two kinds of job (entry of figures from a typescript and edition of the text displayed on the screen), the work capacity, the degree of the visual strain and the operators' subjective symptoms were determined for four lighting levels (200, 300, 500 and 750 lx). It was found that the work at VDT workstations may overload the visual system and cause eyes complaints as well as the reduction of accommodation or convergence strength. It was also noted that the edition of the text displayed on the screen is more burdening for operators than the entry of figures from a typescript. Moreover, the examination results showed that the lighting at VDT workstations should be higher than 200 lx and that 300 lx makes the work conditions most comfortable during the entry of figures from a typescript, and 500 lx during the edition of the text displayed on the screen.

Adult↗

PubMed1994

Study of forward sloping seats for VDT workstations.

The main focus of this study was to identify and evaluate various forward seat inclinations (5, 10, 15 degrees) for Video Display Terminal workstation type seating by constructing a fixture to be fitted to a test chair to achieve various seat angles. The discomfort in critical areas i.e. neck and lower back were evaluated by 25 male university students (avg. age 22 years) with no history of musculoskeletal disorders on a subjective scale for comfort. The comfortable or uncomfortable seat inclinations were identified after a statistical analysis. The heart rate and blood pressure were observed every 5 min for validation purposes. It was recommended that, to avoid neck problems, a chair with a forward incline greater than 5 degrees should not be used and to avoid lower back problems a chair with a seat angle of approximately 10 degrees be used. On the overall comfort criteria it is recommended to use a chair with a seat pan which inclines to approximately 15 degrees (forward). The findings and recommendations from this study can enhance the safety and productivity of the people whose jobs require continuous forward bending in a sitting task involving VDT workstations.

Adult↗

PubMed1994

[Electroencephalographic findings in evaluation of suitability for working with video terminals].

The subjects in the study were 327 bank employees (291 women and 36 men) aged between 21-60 years, with 6-20 years of experience in working with video display units, and 78 persons (73 women and 5 men), aged 18-24 years, who intended to start working with video display units and had no previous work experience. Electroencephalography was among the tests applied in periodical medical examinations of VDU workers and at the preemployment examination of candidates for a VDU job. In 3.4% of the examined VDU workers borderline changes were detected and in 15.0% disrhythmic changes were found. At preemployment examination 35.9% of the electroencephalographic findings were borderline, 23.1% showed slight disrhythmic changes, and 6.4% showed diffuse disrhythmic changes with or without lateralization. Although the study did not establish any particular relationship between VDU work and electroencephalographic findings, in the author's opinion electroencephalography can be recommended in periodical medical examinations of employed persons as well as at preemployment medical examinations. Electroencephalographic findings showing deviations from normal stress the need for a more careful health control. The changes detected at preemployment examination, if a person in spite of certain electroencephalographic abnormalities has been given a job involving VDU work, can be used later on for a realistic assessment of the potential risk/effects relationship.

Adolescent↗

PubMed2001

A field evaluation of monitor placement effects in VDT users.

Appropriate visual display terminal (VDT) location is a subject of ongoing debate. Generally, visual strain is associated with higher placement, and musculoskeletal strain is associated with lower placement. Seeking resolution of the debate, this paper provides a comparison of results from previous lab-based monitor placement studies to recommendations and outcomes from viewing preference and neutral posture studies. The paper then presents results from a field study that addressed two outstanding issues: Does monitor placement in a workplace elicit postures and discomfort responses similar to those seen in laboratory settings? Results showed placements in the workplace elicited postures similar to those in lab studies. Additionally, preferred VDT location generally corresponded to the location in which less neck discomfort was reported, though that trend requires further investigation. Overall, there seems to be consistent evidence to support mid-level or somewhat higher placement, as a rule-of-thumb, considering preferred gaze angle and musculoskeletal concerns. However, optimal placement may be lower for some individuals or tasks.

Adult↗

PubMed2005

The relationship between Video Display Terminals (VDTs) usage and dermatologic manifestations: a cross sectional study.

BACKGROUND: Recently, it has been observed that Video Display Terminals (VDTs) usage for long periods can cause some dermatological manifestations on the face. An analytical cross-sectional study was designed in order to determine this relationship. METHODS: In this study, 600 office workers were chosen randomly from an organization in Tehran (Iran). The subjects were then divided into two groups based on their exposure to VDTs. 306 workers were considered exposure negative (non VDT user) who worked less than 7 hours a week with VDTs. The remainders 294 were exposure-positive, who worked 7 hours or more with VDTs. The frequency of dermatologic manifestations was compared in these two groups. RESULTS: In the exposure-positive and exposure-negative groups, the frequency of these dermatologic manifestations were 27 and 5 respectively. After statistical analysis, a P.value of < 0.05 was obtained indicating a statistically significant difference between these two groups for dermatological manifestations. CONCLUSION: According to our study, there is a relationship between dermatologic manifestations on the face and exposure to VDTs.

Adult↗

PubMed1994

Locomotor strain syndrome in users of video display terminals.

The results of an investigation of fatigue and pain in the locomotor system are presented. The investigation comprised a group of workers (n = 56) who spent most of their working hours at video display terminals (VDTs), and a control group (n = 39) of workers with a mainly free rhythm of work and insignificant physical strain. Fatigue and pain occurred more frequently in the muscles and joints of the workers working on VDT's (78.8:59%), although the differences did not reach statistical significance. On the basis of a rheumatological examination and earlier medical documentation a diagnosis of cervical syndrome was more frequently determined in the VDT group (23.2%) than in the control group (10.3%), while low back pain was diagnosed equally in both groups (17.5%). According to subjective estimation in 46.9% of VDT workers and in 17.9% of the controls disorders were associated with unsatisfactory work conditions. The need for relaxation exercises at the workplace and for the introduction of ergonomic principles for work with VDTs is discussed, particularly with regard to adaptation of the work chair, table, text-stand and foot-rest, and the need to respect anthropometric requirements and working hours. The benefit of movement and isometric exercises at the workplace is emphasized.

Adult↗

PubMed2003

Effects of taurine supplementation on VDT work induced visual stress.

In order to evaluate the effects of dietary taurine supplementation on visual fatigue induced by visual display terminals (VDT) work, 25 male college students aged from 20 to 24 years who were not engaged in VDT work were selected to participate in the study. Volunteers were randomly assigned to either the taurine supplementation (n=13) or the placebo supplementation control group (n=12). Before and after 12 days of taurine (3 g/day) or placebo supplementation, two identical 2.5-hr VDT work tests were performed while recording the P100, N75 and N145 latencies and P100 amplitude of pattern visual evoked potential (PVEP) and the frequency of critical flicker fusion (CFF). Following 2.5-hr of VDT work, the P100 and N75 latencies of PVEP increased ( P<0.01) while the P100 amplitude decreased significantly ( P<0.01). The frequency of CFF also reduced significantly ( P<0.01). After 12 days of taurine supplementation, the reduction in P100 amplitude after VDT work alleviated significantly ( P<0.05). The results suggest that taurine supplementation alleviates visual fatigue induced by VDT work.

Adult↗

PubMed1992

Video display terminal operation: a potential risk in the etiology and maintenance of temporomandibular disorders.

Surveys indicate over 50 million Americans, mostly women, currently operate video display terminals (VDTs) at home or in the workplace. Recent epidemiological studies reveal more than 75% of approximately 30 million American temporomandibular disorder (TMD) sufferers are women. What does the VDT and TMD have in common besides an affinity for the female gender? TMD is associated with numerous risk factors that commonly initiate sympathetic nervous system and stress hormone response mechanisms resulting in muscle spasms, trigger point formation, and pain in the head and neck. Likewise VDT operation may be linked to three additional sympathetic nervous system irritants including: (1) electrostatic ambient air negative ion depletion, (2) electromagnetic radiation, and (3) eyestrain and postural stress associated with poor work habits and improper work station design. Additional research considering the roles these three factors may play in the etiology of TMD and other myofascial pain problems is indicated. Furthermore, dentists are advised to educate patients as to these possible risks, encourage preventive behaviors on the part of employers and employees, and recommend workplace health, safety, and ergonomic upgrades when indicated.

Air Ionization↗

PubMed1997

The perception of flicker on raster-scanned displays.

Experiments have verified the observations of Corbett and White that people are more sensitive to flicker on raster-scanned displays (e.g., television and visual display terminals) if the field scan direction is changed from the conventional top-to-bottom direction to bottom to top, left to right, or right to left. When measured by means of the flicker fusion frequency (FFF), this effect is present only when normal eye movements are permitted. With fixation, the FFF is similar for all scan directions. The effect is demonstrated by the different frequencies at which a directional component is detected in the flicker (which we have called the rolling flicker threshold frequency, or RFTF); the RFTF is lower for top-to-bottom scanning. The effect does not appear to be associated with any asymmetry in eye movements or with eccentricity of the retinal image. The hypothesis that this difference is a consequence of adaptation to televisions and VDTs is supported by the observation that the effect's magnitude correlates with daily exposure time to televisions and VDTs and by a pilot study showing that the effect is reduced when one views a television scanned from bottom to top for 1 h.

Adult↗

PubMed1998

Effects of armrests on workload with ten-key operation.

The constrained posture used for work using a visual display terminal (VDT), such as data entry, can produce static muscular fatigue. Based on the application of ergonomic principles, we conducted an experiment using a prototype VDT chair designed with an armrest adjustable to heights from 22 to 28 cm. The experiment--conducted to assess the static muscular strain based on varying heights of the armrest and distance from the keyboard--was performed with male subjects. The subjects were asked to input five-figure numbers using the 10 keys arranged on the right side. Using a surface electromyogram, we measured the strain imposed on the arm and the shoulder. This was followed up with a performance, weight-loading onto the armrests and a questionnaire. Results show that use of armrests is effective for the alleviation of muscles in one-handed keyboard operation where operators work on a desk whose height is unadjustable according to their body height or where operators are unable to rest their wrist on the desk. A chair with height-adjustable armrests is considered desirable when used by several people.

Adult↗

PubMed1998

[Survey of pathology associated with the use of video display terminals].

This study has been conducted in Sénégal, where Video Display Terminals (VDT) constitute for more than one decade an occupational tool for thousands of workers. Its objectives were to identify symptoms on VDT operators and to state the hazards related to its use. The methodology consists of a Cross sectional study using questionnaire based on the model proposed by the National Research and Security Institute of Paris (INRS). The study target was workers in 4 industries of the capital city Dakar, where VDT have been widely used. 152 persons have been questioned; 50.7% were male. 82.9% of complaints are related to musculosqueletic disorders mainly located in the low back, the neck, and the shoulders. Ergonomics problems appears to be the main cause of these symptoms; no replacement medical examination was performed and as the result, 23.6% did benefit from an ophthalmologic check-up in the 2 years following the use of VDT. Ergonomic evaluation of the working environment as well as medical surveillance are necessary to prevent occurrence of symptoms on VDT users in our country.

Adult↗

PubMed1992

[The influence of VDT work on accommodation].

In order to evaluate the influence of visual display terminal (VDT) work on accommodation, accommodation responses, such as accommodation latency, accommodation velocity, amount of accommodation and refractive power, were measured with an infra-red optometer (TER-7 NIDEK). Comparisons were also made between parameter before VDT work and after VDT work. At first, comparison of the accommodation responses of playing with a video game, being engaged in VDT work and paper work, was made in 5 subjects. There was no significant difference after playing with the video game, slight accommodative dysfunction occurred after being engaged in paper work, but the accommodative dysfunction was most remarkable after being engaged in VDT work. In the next study, the accommodation responses of 22 subjects engaged in VDT work were measured. It was found that there was no significant change in accommodation latency, but a decrease of contraction velocity and relaxation velocity for accommodation was observed, and also a decrease in the amount of contraction response and relaxation response for accommodation was observed. Myopic change during relaxation also occurred. These results suggested that VDT work induced accommodation dysfunction.

Accommodation, Ocular↗

PubMed2003

Effects of VDT tasks with a bright display at night on melatonin, core temperature, heart rate, and sleepiness.

The effects of performing video display terminal (VDT) tasks with a bright display (BD) at night on nocturnal salivary melatonin concentration, rectal temperature, heart rate, and sleepiness were examined. Seven healthy male adults performed exciting VDT tasks with a BD and a dark display (DD) and boring VDT tasks with a BD and a DD from 2300 to 0200. The light intensities of the BD and DD were 45 and 15 lx at each subject's eye level, respectively. The exciting VDT task with both BD and DD significantly suppressed the nocturnal decrease in rectal temperature and heart rate and the nocturnal increase in sleepiness. The BD significantly suppressed the nocturnal decrease in rectal temperature during both exciting and boring VDT tasks. The nocturnal salivary melatonin concentration was significantly suppressed by the combination of the exciting task and BD. The results suggest that performing an exciting VDT task with a BD suppresses the nocturnal changes in melatonin concentration and other physiological indicators of human biological clocks.

Adult↗

PubMed1992

Vision problems at video display terminals: a survey of optometrists.

One thousand three hundred seven optometrists responded (25.3 percent response rate) to a mail questionnaire concerning VDT patients in their practice. On the average, 14.25 percent of optometric patients present with symptoms primarily associated with use of the VDT, or almost 10 million examinations annually when projected to the U.S. population. A majority (55.3 percent) reported that their VDT patients have symptoms that are different than other near point workers, especially as related to glare, lighting, unique viewing conditions and spectacle requirements, and the greater frequency and severity of symptoms. They judged that they were unable to arrive at a confident diagnosis and treatment plan for 20.87 percent of VDT patients, which was significantly more than the 14.05 percent for non-VDT patients. Uncorrected refractive errors, accommodative disorders, irritated eyes, binocular vision disorders, and spectacle design problems were the most frequently cited diagnoses. On the average, 39.3 percent of their VDT patients receive a special VDT prescription or spectacle design that is different than they would require for other daily activities. They judged that 36.8 percent of the symptoms were related to visual environmental factors, primarily glare, lighting, screen resolution and work arrangement. The best way to resolve symptoms for VDT workers is to provide thorough vision examination and treatment in conjunction with diagnosis and treatment of visual environmental problems.

Computer Terminals↗

PubMed1997

Work with video display terminals and the risk of reduced birthweight and preterm birth.

To determine whether the use of video display terminals (VDTs) is associated with an increased risk of reduced birthweight (RBW) and preterm birth, a cohort of telephone operators who used VDTs at work was compared to a cohort of non-VDT-users. Among 2,430 women interviewed, 713 eligible singleton live births were reported. Exposure was estimated from company records and a representative sample of electromagnetic fields was measured at the VDT workstations. For RBW (< or = 2,800 g), we found no excess risk associated with any VDT use during pregnancy (odds ratio [OR] = 0.9; 95% confidence interval [CI] = 0.5-1.7). For preterm birth (< or = 37 weeks), we similarly found no excess risk (OR = 0.7; 95% CI = 0.4-1.1). The risks estimated did not change substantially when hours working with VDTs were used as exposure variables. By contrast, increased risks were found for several known risk factors for LBW and preterm birth. We conclude that occupational VDT use does not increase the risk of RBW and preterm birth.

Adult↗

PubMed2002

Association between duration of daily VDT use and subjective symptoms.

BACKGROUND: Although visual display terminal (VDT) work has become a common task among office workers, surveys which would help to determine the allowable duration of daily VDT use are limited. METHODS: We investigated more than 25,000 workers three times over a 3-year period using a self-administered questionnaire. Three factors, namely mental, physical and sleep-related symptoms, were extracted by factor analysis. Adjusted means of each factor score were compared with the duration of daily VDT use by general linear model. RESULTS: Physical symptoms score became higher with increasing duration of daily VDT use without a threshold effect. Mental and sleep-related symptom scores of the workers using VDT for more 5 hr/day were significantly higher than that of the groups using VDT for >1, 1-3, and 3-5 hr/day. CONCLUSIONS: Duration of daily VDT use was linearly related to the physical symptom score, and was non-linearly related to mental and sleep-related symptom score with a threshold effect of 5 hr/day.

Adult↗

PubMed2003

Posture, muscle activity and muscle fatigue in prolonged VDT work at different screen height settings.

With the increasing use of video display terminals (VDTs), there is growing concern over the corresponding increase in the number of health problems reported. Although much research has focused on identifying the optimal screen height, there is to date no consensus. This study aimed to investigate the effect of prolonged (89 min) VDT work at four different screen heights on head-neck posture, muscle activity and the development of muscle fatigue. The results show that lowering screen height, starting from 15 cm above the baseline (i.e. top of the screen level with eye height while sitting), decreased the ear-eye angle, increased the viewing angle, increased the viewing angle relative to the ear-eye line, and increased the muscle activity of the neck extensor muscles. There were also some significant time effects on postural angles and muscle activity. In this study there were only rare occurrences of muscle fatigue, defined as a simultaneous increase in EMG amplitude and a shift of the EMG power spectrum to lower frequencies. Muscle activity increased significantly in some muscles and for certain screen heights.

Adult↗

PubMed1997

Measurement variability in upper extremity posture among VDT users.

Hand and arm posture while keying is frequently mentioned as a risk factor for upper extremity musculoskeletal disorders (UEMSDs) among video display terminal (VDT) operators. However, many epidemiologic studies have not included measures of posture of VDT operators, in part, because of the difficulty of assessing posture rapidly and reliably among large numbers of subjects. For a single measure of posture to be useful for estimating dose-response relationships between posture and risk of UEMSDs, the within-subject variability of the postural measure must be smaller than the between-subject variability of the postural measure. In addition, the measure must be stable over time. We estimate the ratio of between- to within-subject variability for manual goniometry by measuring six postural angles on six occasions among 19 subjects using VDTs. For each postural angle, between-subject variability was substantially and statistically significantly larger than within-subject variability. Stability of postural measures over time was sufficient to justify a single postural measurement in epidemiologic studies. We conclude that manual goniometry can provide useful information about upper extremity posture among VDT users for use in epidemiologic studies of UEMSDs.

Adult↗