Task variables and visual discomfort associated with the use of VDT's

The effect of vertical gaze position on ocular tear film stability

BACKGROUND

An enlarged exposed ocular surface area is known to degrade tear film stability. Little is known of how tear film stability alters with vertical gaze and the change of palpebral fissure height.

METHODS

Tear film break-up time (TBUT; fluorescent dye) and palpebral fissure height were measured in three vertical gaze positions (primary position and 20 degrees up and 20 degrees down) on 23 healthy volunteers. The effect of gaze direction on TBUT was analysed by ANOVA.

RESULTS

Gaze had a significant influence on tear film stability [F(2,44)=27.6, p<0.001]. In up-gaze with an enlarged palpebral fissure height (11.1 +/- 1.4 mm), TBUT was degraded (17.3 +/- 12.7 seconds). In down-gaze and decreased palpebral fissure height (6.7 +/- 1.2 mm) TBUT was extended (43.5 +/- 35.4 seconds).

CONCLUSION

Ocular tear film stability alters with vertical gaze. Our hypothesis is that the change of the palpebral fissure height and the exposed ocular surface area alters the thickness of the lipid layer and with it tear film evaporation.

The relationship among computer work, environmental design, and musculoskeletal and visual discomfort: examining the moderating role of supervisory relations and co-worker support

PURPOSE

The prevalence of work-related upper extremity musculoskeletal disorders and visual symptoms reported in the USA has increased dramatically during the past two decades. This study examined the factors of computer use, workspace design, psychosocial factors, and organizational ergonomics resources on musculoskeletal and visual discomfort and their impact on the safety and health of computer work employees.

METHODS

A large-scale, cross-sectional survey was administered to a US manufacturing company to investigate these relationships (n = 1259). Associations between these study variables were tested along with moderating effects framed within a conceptual model.

RESULTS

Significant relationships were found between computer use and psychosocial factors of co-worker support and supervisory relations with visual and musculoskeletal discomfort. Co-worker support was found to be significantly related to reports of eyestrain, headaches, and musculoskeletal discomfort. Supervisor relations partially moderated the relationship between workspace design satisfaction and visual and musculoskeletal discomfort.

CONCLUSION

This study provides guidance for developing systematic, preventive measures and recommendations in designing office ergonomics interventions with the goal of reducing musculoskeletal and visual discomfort while enhancing office and computer workers' performance and safety.

Computer use and vision-related problems among university students in ajman, United arab emirate

Background:

The extensive use of computers as medium of teaching and learning in universities necessitates introspection into the extent of computer related health disorders among student population.

Aim:

This study was undertaken to assess the pattern of computer usage and related visual problems, among University students in Ajman, United Arab Emirates.

Materials and Methods:

A total of 500 Students studying in Gulf Medical University, Ajman and Ajman University of Science and Technology were recruited into this study. Demographic characteristics, pattern of usage of computers and associated visual symptoms were recorded in a validated self-administered questionnaire. Chi-square test was used to determine the significance of the observed differences between the variables. The level of statistical significance was at P < 0.05. The crude odds ratio (OR) was determined using simple binary logistic regression and adjusted OR was calculated using the multiple logistic regression.

Results:

The mean age of participants was 20.4 (3.2) years. The analysis of racial data reveals that 50% (236/471) students were from Middle East, 32% (151/471) from other parts of Asia, 11% (52/471) from Africa, 4% (19/471) from America and 3% (14/471) from Europe. The most common visual problems reported among computer users were headache - 53.3% (251/471), burning sensation in the eyes - 54.8% (258/471) and tired eyes - 48% (226/471). Female students were found to be at a higher risk. Nearly 72% of students reported frequent interruption of computer work. Headache caused interruption of work in 43.85% (110/168) of the students while tired eyes caused interruption of work in 43.5% (98/168) of the students. When the screen was viewed at distance more than 50 cm, the prevalence of headaches decreased by 38% (50-100 cm – OR: 0.62, 95% of the confidence interval [CI]: 0.42-0.92). Prevalence of tired eyes increased by 89% when screen filters were not used (OR: 1.894, 95% CI: 1.065-3.368).

Conclusion:

High prevalence of vision related problems was noted among university students. Sustained periods of close screen work without screen filters were found to be associated with occurrence of the symptoms and increased interruptions of work of the students. There is a need to increase the ergonomic awareness among students and corrective measures need to be implemented to reduce the impact of computer related vision problems.

Office ergonomics training and a sit-stand workstation: effects on musculoskeletal and visual symptoms and performance of office workers

Work Related Musculoskeletal Disorders (WMSDs) among office workers with intensive computer use is widespread and the prevalence of symptoms is growing. This randomized controlled trial investigated the effects of an office ergonomics training combined with a sit-stand workstation on musculoskeletal and visual discomfort, behaviors and performance. Participants performed a lab-based customer service job for 8 h per day, over 15 days and were assigned to: Ergonomics Trained (n = 11) or Minimally Trained (n = 11). The training consisted of: a 1.5-h interactive instruction, a sit/stand practice period, and ergonomic reminders. Ergonomics Trained participants experienced minimal musculoskeletal and visual discomfort across the 15 days, varied their postures, with significantly higher performance compared to the Minimally Trained group who had a significantly higher number of symptoms, suggesting that training plays a critical role. The ability to mitigate symptoms, change behaviors and enhance performance through training combined with a sit-stand workstation has implications for preventing discomforts in office workers.

A replicated field intervention study evaluating the impact of a highly adjustable chair and office ergonomics training on visual symptoms

OBJECTIVE

Examine the effects of two office ergonomics interventions in reducing visual symptoms at a private sector worksite.

METHODS

A quasi-experimental study design evaluated the effects of a highly adjustable chair with office ergonomics training intervention (CWT group) and the training only (TO group) compared with no intervention (CO group). Data collection occurred 2 and 1 month(s) pre-intervention and 2, 6 and 12 months post-intervention. During each data collection period, a work environment and health questionnaire (covariates) and daily health diary (outcomes) were completed. Multilevel statistical models tested hypotheses.

RESULTS

Both the training only intervention (p<0.001) and the chair with training intervention (p=0.01) reduced visual symptoms after 12 months.

CONCLUSION

The office ergonomics training alone and coupled with a highly adjustable chair reduced visual symptoms. In replicating results from a public sector worksite at a private sector worksite the external validity of the interventions is strengthened, thus broadening its generalizability.

A field intervention examining the impact of an office ergonomics training and a highly adjustable chair on visual symptoms in a public sector organization

OBJECTIVE

Examine the effect of a multi-component office ergonomics intervention on visual symptom reductions.

METHODS

Office workers were assigned to either a group receiving a highly adjustable chair with office ergonomics training (CWT), a training-only group (TO) or a control group (C). A work environment and health questionnaire was administered 2 and 1 month(s) pre-intervention and 3, 6, and 12 months post-intervention. Multi-level statistical models tested hypotheses.

RESULTS

The CWT intervention lowered daily visual symptoms (p < 0.01) post-intervention. The TO group did not significantly differ from the control group. The CWT group differed significantly from the TO group (p = 0.01) post-intervention.

CONCLUSION

Workers who received a highly adjustable chair and office ergonomics training had reduced visual symptoms and the effect was maintained through twelve months post-intervention. The lack of a training-only group effect supports implementing training in conjunction with the highly adjustable chair to reduce visual symptoms.

Computer use, symptoms, and quality of life

PURPOSE

To model the effects of computer use on reported visual and physical symptoms and to measure the effects upon quality of life measures.

METHODS

A survey of 1000 university employees (70.5% adjusted response rate) assessed visual and physical symptoms, job, physical and mental demands, ability to control/influence work, amount of work at a computer, computer work environment, relations with others at work, life and job satisfaction, and quality of life. Data were analyzed to determine whether self-reported eye symptoms are associated with perceived quality of life. The study also explored the factors that are associated with eye symptoms. Structural equation modeling and multiple regression analyses were used to assess the hypotheses.

RESULTS

Seventy percent of the employees used some form of vision correction during computer use, 2.9% used glasses specifically prescribed for computer use, and 8% had had refractive surgery. Employees spent an average of 6 h per day at the computer. In a multiple regression framework, the latent variable eye symptoms was significantly associated with a composite quality of life variable (p = 0.02) after adjusting for job quality, job satisfaction, supervisor relations, co-worker relations, mental and physical load of the job, and job demand. Age and gender were not significantly associated with symptoms. After adjusting for age, gender, ergonomics, hours at the computer, and exercise, eye symptoms were significantly associated with physical symptoms (p < 0.001) accounting for 48% of the variance.

CONCLUSIONS

Environmental variability at work was associated with eye symptoms and eye symptoms demonstrated a significant impact on quality of life and physical symptoms.

Effects of two eye drop products on computer users with subjective ocular discomfort

BACKGROUND

An increasing number of people seek medical attention for symptoms of visual discomfort due to computer vision syndrome (CVS). We compared the efficacy and adverse event rates of a new eye lubricant, OptiZen (InnoZen, Inc., polysorbate 80 0.5%) and Visine Original (Pfizer Consumer Healthcare, tetrahydrozoline HCl 0.05%).

METHODS

In this double-blind parallel arm trial, 50 healthy men and women, ages 18 to 65 years, with symptoms of CVS who use a video display terminal for a minimum of 4 hours per day were randomized to OptiZen (n = 25) or Visine Original (n= 25), 1 to 2 drops b.i.d. for 5 days. The primary end-points were ocular discomfort and adverse events.

RESULTS

OptiZen and Visine Original had similar efficacy in alleviating symptoms of ocular discomfort (odds ratio of 1.23 [95% confidence interval, 0.63 to 2.42], P= 0.55). OptiZen and Visine Original were very similar with respect to odds ratios and 95% confidence interval (CI) for each of the measurement times (P= 0.72). Visine Original users reported a significantly higher incidence of temporary ocular stinging/burning immediately after drug instillation (28%, 7/25) than did OptiZen users (4%, 1/24) (P= 0.05). Patients using OptiZen were 89% less likely to have stinging/burning effects than those patients using Visine Original (95% CI: 0.01 to 0.95).

DISCUSSION

OptiZen and Visine Original are effective at alleviating ocular discomfort associated with prolonged computer use. Adverse event findings suggest that OptiZen causes less ocular discomfort on instillation, potentially attributable to its milder ingredient profile.

Dynamic accommodation responses to stationary colored targets

PURPOSE

When the targets or the background in a display are different colors, longitudinal chromatic aberration ensures that there is no single correct accommodative response. The purpose of the present study was to determine whether the response becomes more variable when viewing certain multicolor displays.

METHODS

Accommodative responses of five young participants were measured with a dynamic infrared optometer while they viewed steady targets at a nominal stimulus level of 3 D. Target-on-background color combinations were black on white, black on blue, black on red, blue on red, red on blue, dark blue on red, and dark red on blue.

RESULTS

When compared with the standard black-on-white target, responses to targets with reduced spectral bandwidth were not significantly more variable. In most participants, responses to near-isoluminant targets (e.g., red on blue and blue on red) were not more variable than to the standard target. However, calculated confidence intervals cannot rule out moderate to large changes in variability near isoluminance. Responses to these multicolor targets tended to favor the blue focus.

CONCLUSIONS

In most individuals, viewing multichromatic targets does not increase significantly the variation in accommodative response as compared with broadband black-and-white targets.

Do video display units cause visual problems? - a bedside story about the processes of public health decision-making

PURPOSE

Since the 1980s, it has been common for employers to provide eyesight testing for operators of screen-based equipment (SBE). This practice arose because many SBE operators reported symptoms of visual discomfort at work and there was apprehension that radiation emitted by SBE might be harmful to vision. Visual screening of SBE operators has been encouraged by government guidelines and in some countries, is required by legislation. This paper questions whether this practice should continue.

METHOD AND RESULTS

A review of the literature shows: 1. SBE does not emit radiation in sufficient quantity to be harmful and there is no credible epidemiological evidence that work with SBE will damage the eyes; 2. SBE operators often report symptoms of visual discomfort but office workers who do not use SBE also report visual symptoms with the same or slightly lower frequency; 3. about 20 per cent of office workers have some uncorrected defect of vision that can contribute to the occurrence of visual discomfort at work and optometric intervention to correct these defects does reduce the occurrence of visual symptoms. However, defects of vision are not the only cause of visual symptoms at work. Other contributing factors are poor workplace ergonomics and psychosocial stress arising from poor work systems or poor inter-personal relationships at work.

CONCLUSIONS

There is no compelling public health justification for requiring vision screening of SBE operators but it could be introduced as one element of a more comprehensive strategy to enhance visual comfort at work. If it is introduced, it should be for all employees engaged in visually demanding tasks, not just SBE users. An alternative to eyesight testing of employees is to encourage but not require employees to obtain eye care privately on their own initiative. This option has the advantage of restoring autonomy to employees to arrange their own eye care. Eyesight testing of employees in vision-critical occupations should be undertaken to ensure safety. In occupations in which there is a risk of eye injury, vision screening should be undertaken to provide a pre-injury record of vision.

Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals

OBJECTIVES

To clarify the relation between the prevalence of dry eye syndrome and subjective symptoms of asthenopia in visual display terminal (VDT) operators.

METHOD

722 VDT workers (242 subject workers with symptoms of asthenopia and 480 controls without such symptoms) without obvious organic ocular diseases received an ophthalmological examination consisting of refractometry and a tear function (phenol red thread) test.

RESULTS

More than 30% of symptomatic workers were found to meet the criteria of dry eye, and the odds ratio compared with the controls was 4.61 (p < 0.001). This odds ratio was significantly greater than that obtained for refractive errors (2.31).

CONCLUSIONS

Although this cross sectional study could not prove that dry eyes are the cause of asthenopia, the profound association of dry eyes with symptoms of asthenopia could be verified. It would be useful to carry out tear function tests in workers with symptoms of asthenopia.