Visual Display Terminal Tasks Research Articles

Safety and Efficacy of Photocatalytic Micro-Mist Desktop Humidifier for Dry Eye Caused by Digital Environment: A Randomized Controlled Trial.

Background/Objectives: Modern life is inconceivable without visual display terminal (VDT) work, including smartphones, computers, and games for both children and adults. VDT work under air conditioning and low humidity poses a high risk of dry eye and digital eye strain. Methods: Thirty-one participants were randomly divided into two groups using a desktop humidifier with photocatalytic technology, namely the "with mist" (humidifier) group and "without mist" (control) group. Participants performed VDT tasks using the humidifier with or without mist for 1 h. Ocular subjective symptoms and objective tear film parameters were assessed before, immediately after, and 1.5 h after the VDT task with or without mist. (Registry ID: UMIN000054379) Results: Ocular symptom scores improved significantly in the humidifier group immediately after the VDT task and up to 1.5 h later compared to before the task (p < 0.001, =0.006, respectively). Immediately after the VDT task, tear meniscus height was significantly higher and non-invasive breakup time was significantly longer in the humidifier group than in the control group (p < 0.001, =0.040, respectively). Plugging of the meibomian gland orifices was significantly reduced only in the humidifier group immediately after the VDT task compared to before the VDT task and remained significantly reduced up to 1.5 h later (p = 0.004, 0.016, respectively). Conclusions: The use of the photocatalytic desktop humidifier during VDT task resulted in significant improvements in the tear film parameters and subjective symptoms. The photocatalytic desktop humidifier could be effective in alleviating dry eye and eye strain in computer users in a modern office environment.

Relationship between using tables, chairs, and computers and improper postures when doing VDT work in work from home.

This study focused on everyday furniture and computers used in work from home and aimed to investigate how improper postures increase the risk of musculoskeletal disorders using different combinations of tables, chairs, and computers. Twenty-one healthy participants were asked to perform a visual display terminal task for 30 minutes in a laboratory modeled on the work from home concept. Seven experimental conditions were set up according to the different combinations of desks, chairs, and computers. Three-dimensional body posture was measured using a magnetic tracking device. The results showed that when using a low table, floor chair, and laptop computer, the body posture above the hip was similar to that when using a dining table, chair, and desktop computer. When using a sofa, and tablet computers, or laptop computer, severe neck flexion, which is stressful to the neck, was observed. Moreover, excessive low back flexion was observed when using a floor cushion and laptop computer. We suggest that computer work while sitting on a sofa or floor cushion without a backrest is harmful to the neck and low back.

Evaluation of VDT-Induced Visual Fatigue by Automatic Detection of Blink Features.

This study evaluates the progression of visual fatigue induced by visual display terminal (VDT) using automatically detected blink features. A total of 23 subjects were recruited to participate in a VDT task, during which they were required to watch a 120-min video on a laptop and answer a questionnaire every 30 min. Face video recordings were captured by a camera. The blinking and incomplete blinking images were recognized by automatic detection of the parameters of the eyes. Then, the blink features were extracted including blink number (BN), mean blink interval (Mean_BI), mean blink duration (Mean_BD), group blink number (GBN), mean group blink interval (Mean_GBI), incomplete blink number (IBN), and mean incomplete blink interval (Mean_IBI). The results showed that BN and GBN increased significantly, and that Mean_BI and Mean_GBI decreased significantly over time. Mean_BD and Mean_IBI increased and IBN decreased significantly only in the last 30 min. The blink features automatically detected in this study can be used to evaluate the progression of visual fatigue.

Ergonomic Study of VDT Workstations for Wheelchair Users

ABSTRACT This study presents a three-dimensional computer-modelling system based on Transom JACK software, with 3D objects/equipment and human subjects with specific anthropometric measurements to visualize and evaluate human-machine interaction. A computer simulation method is then adopted to evaluate some VDT (Visual Display Terminal) workstations to determine whether they are appropriate for use by wheelchair users. The study indicates that currently available commercial computer desks present difficulties, in terms of both spatial design and reachability of peripheral devices, to wheelchair users. Some VDT tasks result in awkward body postures in virtual subjects. New VDT workstations are designed and recommended to solve the shortcomings found.

Curved Versus Flat Monitors: Interactive Effects of Display Curvature Radius and Display Size on Visual Search Performance and Visual Fatigue.

The aim of this study is to examine the interactive effects of display curvature radius and display size on visual search accuracy, visual search speed, and visual fatigue. Although the advantages of curved displays have been reported, little is known about the interactive effects of display curvature radius and size. Twenty-seven individuals performed visual search tasks at a viewing distance of 50 cm using eight configurations involving four display curvature radii (400R, 600R, 1200R, and flat) and two display sizes (33″ and 50″). To simulate curved screens, five flat display panels were horizontally arranged with their centers concentrically repositioned following each display curvature radius. For accuracy, speed, and fatigue, 33″-600R and 50″-600R provided the best or comparable-to-best results, whereas 50″-flat provided the worst results. For accuracy and fatigue, 33″-flat was the second worst. The changes in the horizontal field of view and viewing angle due to display curvature as well as the association between effective display curvature radii and empirical horopter (loci of perceived equidistance) can explain these results. The interactive effects of display curvature radius and size were evident for visual search performance and fatigue. Beneficial effects of curved displays were maintained across 33″ and 50″, whereas increasing flat display size from 33″ to 50″ was detrimental. For visual search tasks at a viewing distance of 50 cm, 33″-600R and 50″ 600R displays are recommended, as opposed to 33″ and 50″ flat displays. Wide flat displays must be carefully considered for visual display terminal tasks.

VDT 작업에서 두부전방자세 위험수준에 따른 목의 피로와 Flexion-Relaxation 변수에 관한 연구

Objective: The aim of this study is to quantify the neck fatigue of the office in Visual Display Terminal (VDT) work using the parameters of the flexion-relaxation phenomenon. Background: VDT work comprises a large proportion of the office worker tasks. Although VDT work requires relatively less loads, it can stress the neck and shoulders of the workers who work for a long period time with awkward sitting postures. In spite of that many office workers are suffering from neck and shoulder pains, the current solution for musculoskeletal disorders of office workers is only a management approach. Thus, it is important to precisely quantify the fatigue of VDT workers for reducing the prevalence of musculoskeletal disorders in office workers and for improving working environment. Method: For this experiment, 23 males were recruited to compare flexion-relaxation parameters such as Flexion-Relaxation Ratio (FRR) and On/Offset angle, and subjective discomfort (Borg CR-10 scale) before and after VDT task during 50 minutes. Participants were divided into two groups (forward head posture (FHP) high risk group and FHP low risk group) based on the pre-FHP test. Results: FRP parameters changed after VDT task. The FRR was significantly decreased and On/Offset angles showed an increasing trend after the task. CVA was slightly lower in FHP high risk group during 50 minute of VDT task. Using this result, it was found that high risk group of FHP was maintained at a lower posture for a long time. In addition, the subjective discomfort also increased after task. Conclusion: Based on these results, VDT work causes fatigue to the worker. And this fatigue can be quantified using FRP parameters. In addition, it was confirmed that FRR can be used as an index to confirm the abnormality of neck. Application: These results can be used to quantify the fatigue caused by VDT work in office workers, and to further validate the improvement of musculoskeletal disorders.

Effects of Display Curvature, Presbyopia, and Task Duration on Visual Fatigue, Task Performance, and User Satisfaction.

This study examined the effects of display curvature, presbyopia, and task duration on visual fatigue, task performance, and user satisfaction. Although curved displays have been applied to diverse display products, and some studies reported their benefits, it is still unknown whether the effects of display curvature are presbyopia-specific. Each of 64 individuals (eight nonpresbyopes and eight presbyopes per display curvature) performed four 15-min proofreading tasks at one display curvature radius setting (600R, 1140R, 4000R, and flat; mm). Diverse measurements were obtained to assess visual fatigue, task performance, and user satisfaction. The mean pupil diameter was the largest with 1140R, indicating this curvature radius was associated with the least development of visual fatigue; 600R was comparable with 1140R in terms of pupil diameter. The presbyopic group showed a 28.5% slower proofreading speed compared with the nonpresbyopic group, whereas their proofreading accuracy was comparable. For both groups, the mean visual fatigue increased significantly during the first 15 min of proofreading, as indicated by a decrease of 0.11 mm in the mean pupil diameter, an increase of 3.8 in the mean bulbar conjunctival redness, and an increase of 9.13 in the mean eye complaint questionnaire score. The effect of display curvature was not presbyopia-specific. Low visual fatigue was observed with 1140R and 600R. Display curvature radii near or in the range of 600R and 1140R and frequent breaks are recommended for both presbyopic and nonpresbyopic groups to reduce their visual fatigue due to visual display terminal tasks.

안구의 운동방향이 다른 컴퓨터 게임 후 폭주근점과 융합여력의 변화

Purpose: The present study was conducted to investigate whether the directions of eye movement in playing computer games for certain period affected the change of near point of convergence (NPC) and fusional reserve (FR) or not. Methods: Total 40 subjects in 20s who have the visual acuity of 1.0 or higher without any ocular disease and accommodative dysfunction were asked to successively play computer games. After the subjects were moving eyes in horizontal and vertical directions for 40 and 90 minutes, their horizontal fusional reserves, vertical fusional vergence and near point of convergence were measured. Results: The near point of convergence showed a tendency to be receded after computer gaming in the horizontal and vertical directions, and both of horizontal and vertical fusional reserves were significantly reduced. The range of declined fusional reserves and receded near point of convergence after computer gaming for 90 minutes was smaller than those after computer gaming for 40 minutes. The change of binocular vision was affected by the horizontal eye movement rather than the vertical movement when analyzed by the direction of eye movement. Conclusions: This study revealed that the change in FR and NPC was different along with dominant direction of eye movement during visual display terminal (VDT) tasks. Therefore, the adjustment of VDT working time is required to prevent the dysfunction of binocular vision according to the dominant direction of eye movement during VDT task.

Volatiles emitted from the roots of Vetiveria zizanioides suppress the decline in attention during a visual display terminal task

The perennial grass Vetiveria zizanioides (vetiver) is mainly cultivated for its fragrant essential oil. Although the components of the oil and their biological activities have been studied extensively, the effect of the volatiles emitted from the roots of V. zizanioides on humans has so far remained unexplored. We investigated the effects of volatile compounds emitted from the cut roots of V. zizanioides (1.0 g, low-dose conditions; 30 g, high-dose conditions) on individuals during a visual display terminal task. Participants who breathed the volatile compounds emitted under low-dose conditions showed faster reaction times and stimulation of sympathetic nerve activity as measured by electrocardiography. These effects were not observed under high-dose conditions. The total amounnt of volatiles emitted during the experiment was 0.25 μg under low-dose conditions and 1.35 μg under high-dose conditions. These findings indicate that volatile compounds emitted from the roots of V. zizanioides under low-dose conditions may have helped subjects to maintain performance in visual discrimination tasks while maintaining high sympathetic nerve system activity.

The essential oil of Abies sibirica (Pinaceae) reduces arousal levels after visual display terminal work

ABSTRACTVolatile constituents from natural plants have sometimes been used for the treatment of mental disorders, but the efficacy of many plants has not been determined. Here, we investigated the effects of the essential oil of the Siberian fir tree, Abies sibirica (Pinaceae), on individuals during and after performance of a sustained task on a visual display terminal (VDT). Participants who breathed air containing the essential oil showed prolonged heartbeat intervals and increased theta activity as measured by electroencephalography in the recovery period after the VDT task, but not during the task. The volatile constituents emitted from the essential oil of A. sibirica through the odorant delivery system for 40 min were α‐pinene (80.4 µg), santene (3.1 µg), tricyclene (2.4 µg), camphene (24.2 µg), β‐pinene (2.6 µg), myrcene (1.0 µg), δ‐3‐carene (14.4 µg), limonene (3.8 µg), and bornyl acetate (1.0 µg). These results show that the essential oil of A. sibirica reduced arousal levels after the VDT task, and might be useful for the prevention of VDT‐related mental health disturbance. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Blink Rate, Blink Amplitude, and Tear Film Integrity during Dynamic Visual Display Terminal Tasks

Purpose: The present study aimed at investigating the influence of the level of dynamism of two different visual display terminal tasks on spontaneous eyeblink rate, blink amplitude, and tear film integrity.Material and Methods: A total of 25 healthy, young volunteers participated in the study. Blink rate and blink amplitude were recorded in silent primary gaze conditions and while subjects were playing two computer games of similar cognitive demands but different rate of visual information presentation. For each experimental condition, tear volume was evaluated by measuring meniscus height and with the red phenol thread test. Fluorescein and non-invasive break-up time tests, as well as the observation of interference patterns and the estimation of the dry area extension, were employed to assess tear stability.Results: Statistically significant differences were revealed in blink rate (F = 595.85, p < 0.001) and blink amplitude (χ2 = 34.00, p < 0.001), with blink rate during fast- and slow-paced game play decreasing to almost 1/3 and 1/2 of baseline levels, respectively, and with a larger percentage of incomplete blinks during dynamic tasks. Fluorescein and non-invasive break-up time tests and dry area extension were able to differentiate between experimental conditions in general (F = 408.42, p < 0.001; F = 163.49, p < 0.001; χ2 = 20.74, p < 0.001), as well as between fast- and slow-paced games, thus suggesting that tear quality was more affected than tear volume.Conclusions: Blink rate, blink amplitude, and tear film stability were compromised during the most dynamic visual display terminal task, suggesting a negative influence of not only the cognitive aspects of the task, but also of the rate at which new visual information is presented. Frequent breaks and blinking awareness training are recommended for visual display terminal users requiring prolonged periods of visually demanding dynamic computer play or work.

Do Color-Deficient Observers Take Longer to Complete a Color-Related Task?

Previous research has shown that observers with congenital red-green color vision deficiencies (color-deficient) have longer reaction and response times in making color-related judgments compared with individuals with normal color vision (color-normals). The objectives of this study were to determine how much longer color-deficient observers take to complete a visual display terminal (VDT) based color naming test without imposed time constraints, whether there was any correlation between error rate and time to complete the task, to determine the effect of familiarity on the time to complete the task, and whether the completion times were correlated with the anomaloscope or Farnsworth D-15. The VDT task requires individuals to identify colors used to code information in a railway dispatcher display. The test typically takes 8 to 10 min to complete. Eighty-one color-normals and 41 color-deficient observers participated. The total number of errors and time to complete the test were recorded. There were two sessions separated by approximately 2 weeks. The color-deficient group was divided into those that passed the test and those that failed. Pass/fail criteria for the color naming test was established based on the number and types of color-normal errors. The time to complete the task for the color-deficient group who passed was 14% longer than color-normals. Color-deficient observers who failed took 29% longer than color-normals. Mean times to complete the task at the second session were significantly faster (18%) for all three groups with the reduction in time approximately equal across the groups. There was no significant correlation between the number of errors and time to complete or the clinical tests and completion times for any of the three groups. In general, color-deficient observers required more time to the complete the color identification test than color-normals. Although color-deficient observers who failed the VDT test took the longest, there was no correlation between time and the number of errors for any of the subject groups.

Evaluation of mental fatigue based on multipsychophysiological parameters and kernel learning algorithms

Mental fatigue is an extremely sophisticated phenomenon, which is influenced by the environment, the state of health, vitality and the capability of recovery. A single parameter cannot fully describe it. In this paper, the effects of long time sustained low-workload visual display terminal (VDT) task on psychology are investigated by subjective self-reporting measures. Then power spectral indices of HRV, the P300 components based on visual oddball and wavelet packet parameters of EEG are combined to analyze the impacts of prolonged visual display terminal (VDT) activity on autonomic nervous system and central nervous system. Finally, wavelet packet parameters of EEG are extracted as the features of brain activity in different mental fatigue states. Kernel principal component analysis (KPCA) and support vector machine (SVM) are jointly applied to differentiate two states. The statistic results show that the level of both subjective sleepiness and fatigue increase significantly from pre-task to post-task, which indicate that the long time VDT task induces the mental fatigue to the subjects. The predominant activity of autonomic nervous system of subjects turns to the sympathetic activity from parasympathetic activity after the task. The P300 components and wavelet packet parameters of EEG are strongly related with mental fatigue. Moreover, the joint KPCA-SVM method is able to effectively reduce the dimensionality of the feature vectors, speed up the convergence in the training of SVM and achieve a high recognition accuracy (87%) of mental fatigue state. Multipsychophysiological measures and KPCA-SVM method could be a promising tool for the evaluation of mental fatigue.

Effects of VDT Workstation Lighting Conditions on Operator Visual Workload

Industrial lighting covers a wide range of different characteristics of working interiors and work tasks. This study investigated the effects of illumination on visual workload in visual display terminal (VDT) workstation. Ten college students (5 males and 5 females) were recruited as participants to perform VDT signal detection tasks. A randomized block design was utilized with four light colors (red, blue, green and white), two ambient illumination levels (20 lux and 340 lux), with the subject as the block. The dependent variables were the change of critical fusion frequency (CFF), visual acuity, reaction time of targets detection, error rates, and rating scores in a subjective questionnaire. The study results showed that both visual acuity and the subjective visual fatigue were significantly affected by the color of light. The illumination had significant effect on CFF threshold change and reaction time. Subjects prefer to perform VDT task under blue and white lights than green and red. Based on these findings, the study discusses and suggests ways of color lighting and ambient illumination to promote operators' visual performance and prevent visual fatigue effectively.

Carpal tunnel syndrome in male visual display terminal (VDT) workers

The association between working at a video display terminal (VDT) and development of carpal tunnel syndrome (CTS) is not well-established. The study surveyed the prevalence of CTS symptoms, explored the risk factors and evaluated the clinical application of hand diagrams, physical tests and electrodiagnosis among male VDT workers. A cross-sectional study was performed in an information and communication technology company. Three-forty questionnaires were completed and 82 volunteers participated in the physical examination and nerve conduction study. The personal and occupational risk factors for CTS were analyzed. The prevalence of CTS symptoms was 3.8% among 340 subjects, while prolonged median motor distal latency (>4.2 msec) was disclosed in 3.7% of a subgroup receiving examination. Classic/probable CTS symptoms was associated with high body mass index (>28 kg/m(2), odds ratio = 4.1, P = 0.029) and moderate job seniority (3-5 years, odds ratio = 4.6, P = 0.023). Prolonged median motor distal latency was associated with older age (>35 years old). We did not observe correlation between CTS symptoms, abnormal NCS, positive Tinel's sign or Phalen's test. The prevalence of CTS symptoms was not high among the group of male VDT workers studied. Job seniority, but not specific tasks, was associated with CTS symptoms. More reliable and valid methods to quantify the ergonomic exposure are needed to establish the association of VDT tasks and CTS.

Comparison of TFT-LCD and CRT on visual recognition and subjective preference

This study investigated the effects of screen type, contrast ratio, and ambient illumination on visual recognition and subjective preference for visual display terminal (VDT) screen characteristics. Screen type and ambient illumination did not significantly affect visual recognition. The visual recognition was slightly better for 200 lx ambient illumination than for 450 and 700 lx. However, contrast ratio significantly affected visual recognition, with a higher contrast ratio resulting in better visual recognition. Subjective preference was significantly affected by screen type and contrast ratio. Subjects preferred the thin film transistor liquid crystal display (TFT-LCD) to a cathode ray tube (CRT). The subjective preference level improved as the contrast ratio increased. In conclusion, the TFT-LCD did not show significantly better visual recognition than the CRT. However, based on the analysis of the subjective ratings, the TFT-LCD may be the better choice for VDT tasks. Higher contrast ratio resulted in better visual recognition and higher subjective preference. Lower ambient illumination (200 lx) was slightly better in terms of both visual recognition and subjective preference compared to higher ambient illumination (700 lx). Relevant to industry Screen type, contrast ratio, and ambient illumination were the key factors affecting visual recognition and the subjective preference for VDTs. The results from this study may not only improve VDT performance but also may enhance worker satisfaction given their preferences for VDT screen characteristics.

Fatigue estimation of visual display terminal (VDT) workers by physiological data--preliminary study of a new computer program for VDT work analysis

The methods for assessing VDT workload based on individual capabilities are necessary to evaluate general fatigue by VDT work. We have developed a new computer program for assessing data entry performance of each individual. Four healthy male volunteers conducted a data entry task at their own pace using this program under a controlled environment. They performed the task for 30 minutes twice with 10 minutes rest between them. As a result, the average number of inputs was 133.2 characters/min in the first task and 129.1 characters/min after taking the rest. The error rate was 8.6% and 10.6% in each task. This program was useful to evaluate their data entry performance. We also reported our concern with a drop in nasal skin temperature that was observed during these VDT tasks.

Evaluation of Shoulder Muscular Fatigue Induced During VDT Tasks

This study was designed to evaluate localized muscular fatigue induced during visual display terminal (VDT) tasks. In the experimental paradigm used, electromyography (EMG) signals were not recorded during the VDT task but during isometric contractions in which the load imposed on the shoulder muscle was kept constant. The change in mean power frequency (MPF) and the root mean square values of EMG signals with time were explored. The correspondence between these measures and the psychological rating of localized muscular fatigue also were examined. The effectiveness of the experimental paradigm and of the measures used for evaluation of localized muscular fatigue are discussed. MPF measured during isometric contraction was found to be a sensitive measure of localized muscular fatigue.

Proposal of an Index to Evaluate Visual Fatigue Induced During Visual Display Terminal Tasks

The study described in this article was designed to evaluate visual fatigue induced during video display terminal (VDT) tasks. Newly developed equipment was used that can simultaneously measure pupillary change, focal accommodation, and eye movement. The changes in these 3 physiological measures, taken during a VDT task, were used to propose an index for evaluating visual fatigue. Through multiple regression analysis, an index to describe the psychological sense of visual fatigue was obtained. In this index, the minimum pupil diameter, velocity of focal accommodation for constriction, and width of focal accommodation were included. The results suggest that visual fatigue in VDT tasks can be evaluated effectively using both pupil diameter and focal accommodation. The index can be used to assess visual fatigue induced during a VDT task if the following 3 conditions are satisfied: 1. Head movement is limited and infrequent. 2. The task requires focal accommodation. 3. During the task, there is no outstanding change in the lighting environment such as luminous intensity or brightness.

Reasonable Lighting Factors for Work Environment with VDT Tasks

This paper presents a proposal to design factors for a reasonable lighting environment in Visual Display Terminal (VDT) work, by monitoring changes in the lighting environment by general illumination and partial illumination as a factor of the working environment. We also considered that this factor affects productively and workload from an experimental approach. Since we think that it is not enough to evaluate a lighting environment only by subjective appraisal, we used brain waves as a physiological index for evaluating human mental activity objectively. The evaluation index used in the experiment were obtained by measuring working efficiency and working quality in VDT work, mental changes (stability) recorded by an electroencephalograph (EEG), and determined the workload by a survey of subjective symptoms and by measuring eye fatigue. The results enable us to derive a relationship between reasonable lighting environment and illuminance. The results show the following: 1)When the partial illumination was given to subjects, it was shown to effect their concentration on work and mentally stabilize at the ratio of surround illuminannce to horizontal illuminance was about 0.05. 2)When the ratio of surround illuminance to horizontal illuminance was the same, the effect showed remarkable at the ratio of vertical illuminance to horizontal illuminance was lower.