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PubMed2004

[Survey on visual and musculoskeletal symptoms in VDT workers].

With the spread of visual display terminals (VDT) in offices, the numbers of workers using VDT and the working hours at such equipment have increased rapidly in recent years. Also, preventive measures for fatigue have been proposed and the office-working environment has been improved. To examine the effects of the rapid changes in working conditions and environment on the health of VDT workers, we conducted a questionnaire survey in 2002. A self-reported questionnaire was distributed to 3,927 office workers; 2,374 (60.5%) responded. Subjects whose questionnaires had missing data were excluded from analysis. As a result, 1,406 (male: 1,069, female: 337) workers aged 20 to 59 were subjected to analysis. By a logistic regression model, we examined the association between VDT use and visual and musculoskeletal symptoms. Prevalence of eye strain and/or pain (72.1%) was the highest, followed by neck stiffness and/or pain (59.3%), low back stiffness and/or pain (30.0%) and hand or arm strain and/or pain (13.9%). Women consistently reported more discomfort than men. As a result of the logistic regression model, eye strain and/or pain was associated with dissatisfaction with airflow, but not with factors affecting visual symptoms as reported in previous studies, for example, reflection of light and blurred characters on the screen. It was thought that airflow appeared as a risk factor because the lighting environment had been improved in offices to prevent reflection of light on the screen. Neck stiffness and/or pain was associated with raising the shoulders during VDT work, the unsuitable shape of the computer mouse for a hand, and the inconvenient arrangement of the mouse in relation to the body. Hand or arm strain and/or pain were associated with the arrangement of the mouse and inappropriate height of the desk. Low back stiffness and/or pain were associated with dissatisfaction with the chair and using the keyboard without a wrist rest. Although measures to prevent fatigue had been implemented for VDT workers, risk factors for musculoskeletal symptoms would be the same as in previous studies.

Adult↗
PubMed1987

Multi-point flicker recognition apparatus and its application for video display terminal work.

The apparatus to measure multi-point critical flicker fusion frequency (MCFF) was devised for more precise determination of the critical flicker fusion frequency (CFF). Using this apparatus, the variations in flicker value after the work load of the television (TV) game, the Kraepelin using the video display terminal (VDT-Kraepelin) and the paper-Kraepelin were examined in order to test its practical applicability. The following results were obtained. The degree of decrease in the CFF values of some peripheral eye fields was larger than that on the central field of both eyes (ordinary CFF) after work load. The variation rates of the central and the peripheral flicker values were measured before and after loading in each work, and the correlations of variation rates between two CFF values among them were calculated. The numbers of peripheral eye fields showing significant correlation of variation rates between two eye fields in the TV game and the VDT-Kraepelin, were greater than those in the paper-Kraepelin.

Adult↗
PubMed1989

[Visual fatigue evaluation of field sequential stereoscopic 3D display using near point distance].

The purpose of this paper was to evaluate quantitatively visual fatigue encountered in viewing stereoscopic 3D television. By examining the difference in the visual function involved in watching 2D and stereoscopic 3D displays, we could extract only the effect on visual perception in stereoscopic 3D television. Since the visual fatigue with the 3D display may be caused by the discrepancy between convergence and accommodation, the near point distances were measured by an Accommodo Polyrecorder, where Landolt's ring was pursued with binocularity. Five subjects, all employees of NEC Corporation, participated in the experiment. All subjects had normal or corrected-to-normal vision. Two of the subjects watched a 3D video movie. After a week, they watched another video movie in 2D. The rest of them watched the movies in reverse order. One video movie viewing requires about 120 minutes. The near point distances were measured before and after watching for 30, 60, 90 and 120 minutes. The 3D television system used here is a 3D video disc system with field sequence using glasses with liquid crystal shutters. In the case of 2D, each subject wore the glasses whose shutters were kept open. In the experiment, instruction to watch the video movies in a relaxed posture was given. There was a significant effect in regard to 3D/2D treatments on the change rates of the near point distance measured after watching every 30 minutes to one before watching. In addition, the change rates in 3D watching after 60, 90 and 120 minutes were significantly increased, compared with the corresponding rates in 2D.(ABSTRACT TRUNCATED AT 250 WORDS)

Accommodation, Ocular↗
PubMed2005

Prevalence of eye strain among radiologists: influence of viewing variables on symptoms.

OBJECTIVE: To determine the prevalence of and factors contributing to eye strain among radiologists, we examined the influence of the viewing method (PACS vs hard-copy film), age, case volume, technique, work habits, and workstation design on symptoms. MATERIALS AND METHODS: An Internet-based survey was sent to 2,700 radiologists randomly selected from the membership database of the Radiological Society of North America. Questions included demographic information, viewing method, work habits, and workstation design. Common eye strain symptoms were evaluated on a 5-point Likert scale. Chi-square analysis, analysis of variance, and step-wise and regression analyses were performed to evaluate codependence of the explanatory variables with eye strain. RESULTS: The adjusted response rate was 14% (380 respondents). The largest age cohort was 36-50 years. The prevalence of eye strain was 36% and was not affected by the viewing method (PACS vs film). Increased symptoms could be independently predicted in radiologists who were women (p <0.001), had longer work days (p=0.009), took fewer breaks (p=0.03), reported screen flicker (p=0.0003), and performed CT screening (p=0.04). Working hours had the strongest influence on eye strain. Eye strain was increased in those who reported studies for longer than 6 hr per day (p=0.01) and decreased in those who took breaks every hour (p=0.04). Symptoms were independent of the length of the break taken and of other workstation and technique factors. CONCLUSION: Eye strain was common among the radiologists in our study population, with no significant difference between PACS and hard-copy film users. Taking frequent short breaks, eliminating screen flicker, and limiting the number of CT screening studies interpreted may improve symptoms.

Adult↗
PubMed2001

Spontaneous blinks as a criterion of visual fatigue during prolonged work on visual display terminals.

Visual fatigue caused by prolonged work viewing a Visual Display Terminals (VDT) and of work reading a hard-copy were assessed by electromyogram (EMG) waveform and electrooculogram (EOG) waveform in spontaneous blinks as objective criteria, and by questionnaire of subjective feeling, and by task performance. The duration and the amplitude of the EMG of the orbicularis ocular muscle on the right side and the EOG of the vertical direction to the eyelid were measured for 10 subjects who participated in a figure task consisting of the addition of single-digit numbers on a VDT work or a work with a hard-copy. The mean values of the duration and the amplitude of the EMG and the EOG were evaluated by the averaging of 10 waveforms of the spontaneous blinks for all subjects. The time lag from the EMG to the EOG in the process of the generation of spontaneous blinks was also analyzed. These five parameters were evaluated during the work time. The mean values for the duration of the EMG increased gradually during the work time, but the amplitude did not show significant difference between the prework and a work time. There was no significant change of the duration of the EOG, but the mean amplitude of the EOG decreased as the work time progressed, and the time lag significantly extended. The blinks frequency increased relatively when using a VDT. The rate of fluctuation for these parameters was higher during use of a VDT than use of a hard-copy. The time lag at five hours of VDT work was extended by 90% based on the value at the pre-work. The symptoms of general fatigue and fatigue of the eyes increased linearly during the VDT work for six hours. The results indicated a significant correlation between the objective parameters for the activity of the spontaneous blinks, i.e., duration and amplitude of EMG and EOG, and the time lag between EMG and EOG, and the subjective feeling was recognized in the time course of the task. These experimental results suggested that the parameters regarding the EMG and the EOG for the spontaneous blinks were effective indices for assessing visual fatigue during prolonged VDT work.

Adult↗
PubMed1994

Physiological indices of visual fatigue due to VDT operation: pupillary reflexes and accommodative responses.

In spite of the clarification of some significant physiological factors of visual fatigue caused by VDT work, pupillary reflexes have not been studied as to how they are affected after prolonged visual work. This study examined visual function changes objectively in terms of pupillary reflexes and lens accommodative responses after a 4-hr VDT operation task. The relationship between the two functions was also examined. Two measurements in this paper revealed the physiological function changes due to VDT operation. The subjects involved were five students with an average age of 22.6 years. First, near-reflex measurement ascertained decreases in amplitude and the velocity of accommodation function after the visual task. Second, light-reflex measurement revealed a delay of the reflex, an increase in the amplitude of the reflex, and a decrease in pupil size after the visual task. A weak correlation between the decrease in pupil size and accommodation function was found. The occurrence of visual fatigue due to 4-hr VDT operation was also confirmed by CFF measurements and reported subjective visual symptoms in this experiment.

Accommodation, Ocular↗
PubMed1996

Accumulation of VDT work-related visual fatigue assessed by visual evoked potential, near point distance and critical flicker fusion.

To confirm daily accumulation of visual fatigue induced by work with visual display terminals (VDT), visual evoked potential (VEP), near point distance (NPD) and critical flicker fusion (CFF) were measured in three VDT workers and three sex- and age-matched controls (non-VDT workers) in the morning, noontime and evening for five consecutive days (Monday to Friday), totally 15 times per subject. The workers had been engaged in wireless handling operation, with VDTs, of an unmanned power shovel (Worker 1), an unmanned 78-ton dump truck (Worker 2) and mobile monitor-cameras (Worker 3), for 10 months. Their working hours were about 6.5 hours per day; but, the Worker 2 could take a 10-minute recess (a period without VDT work) per about 30 minutes during working hours. Significant daily variations in the VEP latency, NPD and CFF were found in the Worker 1 or Worker 3 despite the absence of any significant daily or diurnal variations in the non-VDT workers; the trends in the variations were getting worse from Monday to Friday. The NPD in the VDT workers was significantly longer than that in each of the matched controls; also, the CFF in the Workers 1 and 3 was significantly depressed. The changes in the VEP latency from morning to noontime and in the NPD and CFF from noontime to evening were significantly larger in the VDT worker than in the matched control. These findings suggest that VDT work probably affects visual function assessed by the VEP, NPD and CFF. Visual fatigue due to long-term VDT work may tend to be accumulated day by day.

Adult↗
PubMed1997

Ergonomic evaluation of working posture of VDT operation using personal computer with flat panel display.

The aim of this study was to evaluate working conditions using a personal computer with a flat panel display (FPD) in terms of visual and musculoskeletal comfort. Measurements of viewing distance, viewing angle, head angle, neck angle and electromyogram (EMG) activities of the neck, shoulder and back muscles of visual display terminal (VDT) operators were compared at workstations using an FPD and a desktop personal computer (DPC). A notebook personal computer (NPC) with a 10.4 inches FPD, was used in this experiment. Each of 10 healthy subjects performed word processing tasks using both NPC and DPC workstations. Significant differences in the work posture while using the NPC and DPC were seen with viewing distance, viewing angle and head angle. The characteristic features of the work posture using the NPC were a remarkably short viewing distance and a forward inclination of the head. The value of integrated EMG (IEMG) of the neck muscle was greater while using the NPC than when using the DPC. These phenomena were caused by the structure of NPCs; most NPCs have a display and keyboard which cannot be separated and are not adjustable without tilt and swivel mechanisms. VDT devices that cannot be adjusted may potentially make operators assume a poor posture while working, which could cause visual and musculoskeletal disorders. To prevent visual and musculoskeletal problems using NPCs, a more upright head and neck position was recommended. The addition of a mechanism for adjustment of the height of an NPC display would allow a comfortable downward gaze without the loss of correct posture.

Adolescent↗
PubMed1994

Eye discomfort and work with visual display terminals.

OBJECTIVES: The aim of this study was to investigate the relationships between eye discomfort symptoms and work with visual display terminals among routine office workers. METHODS: Three hundred and twenty-seven office workers and their work stations were investigated by means of questionnaires and worksite investigations. The data were subjected to multivariate logistic regression analyses. RESULTS: The occurrence of eye discomfort increased as the extent of VDT work increased, as did the specific symptoms of sensitivity to light and smarting, gritting feeling, or redness. The use of spectacles during visual display terminal work, age, stomach stress reaction, distances between the eye and different visual task objects, as well as the vertical position of the terminal also influenced certain symptoms. Having (i) the terminal at about eye level during prolonged terminal work, (ii) using monofocal glasses during terminal work in situations with large distance variations to visual task objects, or (iii) being elderly with prolonged terminal work and reporting stomach stress all led to increased odds ratios for certain eye discomfort symptoms. CONCLUSIONS: The use of a visual display terminal in routine office work is associated with an increased occurrence of certain eye discomfort symptoms. This association is affected also by the presence of certain other individual and ergonomic factors.

Adult↗
PubMed1983

Influence of VDT (visual display terminals) work on eye accommodation.

Visual display terminals (VDT) are popular in offices. Many VDT operators have complained about eye-function impairment. Experiments using an accommodo polyrecorder and an infrared optometer showed that visual tasks in VDT work might induce temporary effects in the visual accommodation system; prolonged the near point distance and the contraction time of accommodation and increased the low frequency component of the small fluctuation of accommodation after VDT work. The inhibition of accommodation caused by VDT work was more severe than that caused by the conventional hard-copy work, and changes in the accommodative function were found with statistical significance in the smaller-size character group but tended to deteriorate in the larger-size character group. The inhibition was more evident in the elderly and middle age groups than in the young age group. The inhibition of accommodation by VDT work might be inhibited by administration of methylcobalamin.

Accommodation, Ocular↗
PubMed1987

Effect of methylcobalamin in accommodative dysfunction of eye by visual load.

The effect of methylcobalamin on the accommodative function of subjects with deteriorated accommodation by induced experimental visual work was studied by measuring small fluctuations of accommodation. The deterioration of small fluctuations of accommodations were difficult to find after visual work in the group receiving methylcobalamin. However, a significant difference of small fluctuations of accommodation was recognized in the non-administered group and in the placebo group (P less than 0.05), and that change was higher in the non-administered group than in the placebo group. Although, the placebo effect of methylcobalamin was undeniable, it was objectively confirmed that methylcobalamin produced a good effect on deteriorated accommodation induced by the visual work.

Accommodation, Ocular↗
PubMed1987

Evaluation of vergent eye movement using the jumping method.

The state of vergent eye movement is reported before and after the experimental work. The work performed by 26 subjects was a name search task on a visual display terminal (VDT). Convergence and divergence eye movements were recorded objectively using an accommodopolyrecorder, and as a sensor of eye movement, elictro-oculogram (EOG) was applied. These eye movements were elicited by watching each target, a far fixation target and a near fixation target, which alternated from far to near every five seconds on the accommodopolyrecorder. Measurements by this method were conducted at two points in time: before beginning the VDT work and after completing the work. The convergence time was unchanged before and after the work load. The divergence time, however, was prolonged after the work load, which was highly significant (P less than 0.001). In this study, it is shown that the vergent eye movement, convergent and divergent eye movement, is influenced by VDT work.

Accommodation, Ocular↗