Optimum display luminance and contrast polarity of desktop head-up display under office lighting level based on visual ergonomic study.

New type desktop head-up display (HUD) can reduce visual fatigue and protect vision through long viewing distance. In this study, participants evaluated visual performance, fatigue, and discomfort of desktop HUD under two contrast polarity (N = 36) and five display luminance levels (N = 21). A positive polarity advantage was found over negative in visual fatigue and discomfort (p < .05). Statistically significant effect of luminance was found on visual performance, fatigue, and discomfort (p < .05). The calculated optimum display luminance by the proposed inverted-U fitted model was 153 cd/m2 under 300 lx, higher than that of traditional desktop displays. It is speculated that higher luminance is required to offset the reduction in contrast sensitivity due to smaller target angular size, which caused by longer viewing distance. These findings suggest that positive polarity and 153 cd/m2 can be used to improve performance and avoid fatigue and discomfort when utilising desktop HUD under 300 lx.

A visual ergonomic study was conducted on new type desktop HUD. With visual performance, fatigue, and discomfort as optimisation goals, positive polarity and 153 cd/m² was recommended under 300 lx. Compared with traditional desktop displays, higher luminance was required in desktop HUD under the same illumination.

Analysis of real-world visual ergonomics at the visual display unit.

INTRODUCTION: In this interventional study, the ergonomic workplace set-up and the impact of character size on subjectively estimated working productivity and computer vision syndrome (CVS) were evaluated in the field. METHODS: The number of displays and their size, resolution, surface structure, position in the room and relation to the eye were evaluated for 152 units. CVS was assessed using the CVS-Questionnaire. Habitually used character size for an uppercase E was recorded and compared to the ISO 9241-303:2011, national standards (e.g., ANSI/HFES 100-2007) and national guidelines (e.g., German DGUV Information 215-410). In case of failure to comply with these standards, character size was increased to 22 angular minutes to reach the recommended ranges. Reasons for returning to former or smaller character sizes were recorded, and subjectively perceived changes in productivity were estimated by the participants using a visual analogue scale before and 2 weeks after the intervention using a questionnaire. RESULTS: The average visual display unit consisted of two non-glare (matt) 24″ widescreen monitors that were located approximately 73 cm (primary) and 76 cm (secondary) from the eyes. The mean (SD) habitually set character size was 14.29 angular minutes (3.53) and therefore both statistically and clinically significantly too small compared with ISO 9241-303:2011 (p < 0.001). Increasing the character size to 22 angular minutes produced a 26% reduction in subjectively rated productivity (p < 0.001). No significant correlation between character size and symptoms of CVS was demonstrated. CONCLUSIONS: In the workplaces investigated, recommendations for character size were not adhered to. This resulted in a reduction in productivity and was not compatible with some of the work requirements, for example, obtaining a broad overview of a spreadsheet.

Visual ergonomics, performance and the mediating role of eye discomfort: a structural equation modelling approach.

The purpose of this study was to model the visual ergonomic factors affecting performance in human-computer interaction. A cross-sectional study using structural equation modelling was performed with a sample of 200 participants. The measuring instruments included the office lighting survey questionnaire, performance assessment questionnaires, visual ergonomics assessment and an eye discomfort assessment. The hypothetical model evaluated workplace lighting status and visual ergonomics as precursors, performance as the output and eye discomfort as a mediator. The results showed that eye discomfort directly affected performance. Visual ergonomics also had a significant direct effect on eye discomfort. The final model suggested a significant new path between the quality of lighting and visual ergonomics. Also, the quality of lighting had an indirect effect on eye discomfort and performance, and the effect of visual ergonomics on performance was the same. Improving the lighting quality and visual ergonomics can reduce eye discomfort and increase performance.

Visual ergonomics for changing work environments in the COVID-19 pandemic.

BACKGROUND: The coronavirus 2019 (COVID-19) pandemic has brought about change in the work environment, increasing remote and hybrid mode of work, presenting a compelling need to study visual ergonomics in this new work environment. OBJECTIVE: To assess computer vision symptoms and visual ergonomics in remote and hybrid work settings during the COVID-19 pandemic with a focus on eye to screen relationship. METHODS: The computer-vision symptom scale (CVSS17) questionnaire and questions about human factors and ergonomics were included in the survey conducted in September 2021. Sixty-six working professionals (mean age 37 years±5), working from home (n = 44) or in hybrid mode (n = 22) were included in the study. Cramer's V was used for the correlation coefficient between two categorical variables for assessing eye health in changing work environments. RESULTS: Compared to our previous study, the correlation between computer vision syndrome (CVS) symptoms is markedly higher. The population working in hybrid mode experienced eye heaviness with strain to see well (V = 0.6872, p = 0.002) and dryness in the eyes (V = 0.5912, p = 0.0179). The population working from home who are bothered by surrounding lights also report dryness in the eyes (V = 0.3846, p = 0.0005). Screen use hours are higher in work from home situations (43% work more than 9 hrs) than those in hybrid mode of work (4% work more than 9 hrs). CONCLUSION: A definite increase in CVS in most of the population working remotely or in hybrid environments is established through this study. User-friendly strategies for raising awareness of applied visual ergonomics can prevent rampant onset of CVS in the working population.

Validación del instrumento "Computer Vision Syndrome Questionnaire (CVS-Q)" para la evaluación del síndrome visual informático en personal de salud de Lima

Objetivos: Determinar la validez y confiabilidad del instrumento "Computer Vision Syndrome Questionnaire (CVS-Q)" en la medición del Síndrome Visual Informático en personal de salud de Lima. Material y métodos: Estudio observacional, descriptivo y de corte transversal, de tipo evaluación de cuestionario, realizado en 82 trabajadores de salud. La validez de contenido se evaluó mediante juicio de expertos con método estadístico de V de Aiken; Validez de constructo, mediante análisis factorial; validez discriminante, a través de la curva operador-receptor (ROC) contrastada con el cuestionario CSSV17; confiabilidad de consistencia interna, con alfa de Cronbach; confiabilidad test - re-test (con 7 días de diferencia); con Rho de Spearman y Coeficiente de Correlación Intraclase (CCI), con intervalos de confianza (IC) del 95%. Se empleó para el procesamiento el software SPSS versión 20.0 para Windows con licencia de prueba. Resultados: El V de Aiken obtuvo un valor de 100%. El análisis factorial extrajo 3 componentes principales que explicaron el 69,455% de la varianza total. El área bajo la curva ROC fue 0,889 [(0,845-0,934); IC=0,95] (p=0,000), sensibilidad 72,22% y especificidad 100%. El alfa de Cronbach fue 0,939, Rho de Spearman 0,884 (p=0,000) y CCI 0,856 [(0,777 - 0,907); IC=0,95] (p=0,000). Conclusiones: El Cuestionario CVS-Q es válido y confiable para ser aplicado sobre el grupo ocupacional de profesionales de la salud con buenas propiedades psicométricas.

SUMMARY Objectives: To determine the validity and reliability of the instrument "Computer Vision Syndrome Questionnaire (CVS-Q)" in the measurement of the Computer Visual Syndrome in health personnel in Lima. Methods: A quantitative, observational, descriptive, cross-sectional and questionnaire study was carried out in 82 health workers. Content validity was evaluated by expert judgment with the Aiken V statistical method; construct validity, through factor analysis; discriminant validity, through the receiver operating characteristic curve (ROC) curve contrasted with the CSSV17 questionnaire; internal consistency reliability, with Cronbach's alpha; reliability test - re-test (7 days apart); with Spearman's Rho and Interclass Correlation Coefficient (ICC) with 95% CI. The SPSS software version 20.0 for Windows with a trial license was used for its processing. Results: The V of Aiken obtained a value of 100%. The factor analysis extracted 3 main components that explain 69.455% of the total variance. The area under the ROC curve was 0.889 [(0.845-0,934); CI=0.95] (p=0.000), sensitivity 72.2% and specificity 100%. Cronbach's alpha was 0.939, Spearman's Rho 0.884 (p=0.000) and ICC 0.856 [(0.777 - 0.907); CI=0.95] (p=0.000). Conclusions: The CVS-Q questionnaire is valid and reliable to be applied in the health professionals' occupational group with good psychometric properties.

Computer vision syndrome, visual ergonomics and amelioration among staff members in a Saudi medical college.

Objectives. Nearly 60 million people suffer from computer vision syndrome (CVS) globally, resulting in reduced work productivity. This study aimed to determine the prevalence of CVS, describe the working conditions, visualize ergonomic factors and determine preventive measures application among university staff members. Methods. A cross-sectional study was conducted with university medical staff members using a semi-structured questionnaire that included a validated CVS questionnaire. Results. CVS prevalence was 81.2%. Dryness, headache, feeling that sight is worsening and difficulty in focusing on near vision were the most experienced symptoms. Prevalence of CVS was significantly higher among females (52.3%), those having a higher mean work duration (21.65 ± 7.55 years), those who frequently use a smartphone (84.9%) and those spending most of their screen time during both day and night (87.1%). Visual ergonomics and preventive measures application, such as correct screen level, regular cleaning of the screen, appropriate illumination and use of eye drops, were significantly associated with negative CVS. Conclusions. These results raised attention to the essential need for visual assessment of university staff members for early and proper diagnosis of CVS to minimize its impact on working performance. Accordingly, it is recommended to organize university-based awareness programs regarding CVS for working personnel.

Neck and upper extremity pain in sonographers - a longitudinal study.

BACKGROUND: Sonographers have reported a high occurrence of musculoskeletal pain for more than 25 years. Assessments of occupational risk factors have previously been based on cross-sectional surveys. The aim of this longitudinal study was to determine which factors at baseline that were associated with neck/shoulder and elbow/hand pain at follow-up. METHODS: A questionnaire was answered by 248 female sonographers at baseline and follow-up (85% of the original cohort). 208 were included in the analyses. Physical, visual, and psychosocial work-related conditions were assessed at baseline. Pain in two body regions (neck/shoulders and elbows/hands) was assessed at both baseline and follow up. RESULTS: Pain at baseline showed the strongest association with pain at follow-up in both body regions [prevalence ratio (PR) 2.04; 95% confidence interval (CI) 1.50-2.76], for neck/shoulders and (PR 3.45; CI 2.29-5.22) for elbows/hands. Neck/shoulder pain at follow-up was associated with inability of ergonomic adjustments at the ultrasound device (PR 1.25; CI 1.05-1.49), a high mechanical exposure index (PR 1.66; CI 1.09-2.52), and adverse visual conditions (PR 1.24; CI 1.00-1.54) at baseline. Moreover, among participants with no neck/shoulder pain at baseline, high job demands (PR 1.78; CI 1.01-3.12), and a high mechanical exposure index (PR 2.0; CI 0.98-4.14) predicted pain at follow-up. Pain in the elbows/hands at follow-up was associated with high sensory demands at baseline (PR 1.63; CI 1.08-2.45), and among participants without pain at baseline high sensory demands predicted elbow/hand pain at follow-up (PR 3.34; CI 1.53-7.31). CONCLUSION: Pain at baseline was the strongest predictor for pain at follow-up in both body regions. We also found several occupational factors at baseline that were associated with pain at follow-up: inability to adjust equipment, adverse visual conditions, a high MEI, high job demands and high sensory demands. These results point at a possibility to influence pain with better ergonomics.

Effect of ciliary-muscle contraction force on trapezius muscle activity during computer mouse work.

The present study aimed to identify whether or not an increase in ciliary-muscle contraction force, when the eye-lens is adjusted for viewing at a near distance, results in an increase in trapezius muscle activity, while performing a natural work task. Twelve participants, ranging in age from 21 to 32 years, performed a computer-mouse work task during free gaze conditions. A moving visual target was tracked with a computer mouse on a screen placed at two different distances from the eyes, 25 cm and 50 cm. Tracking performance, eye accommodation, and bilateral trapezius muscle activity were measured continuously. Ciliary-muscle contraction force was computed according to a formula which takes into account the age-dependent, non-linear relationship between the contraction force of the ciliary muscle and the produced level of eye accommodation. Generalized estimating equations analyses were performed. On the dominant hand side and for the nearest screen distance, there was a significant effect of ciliary-muscle contraction force on the trapezius muscle activity (p < 0.001). No other effects were significant (p > 0.05). The results support the hypothesis that high visual demands, during computer mouse work, increase ciliary muscle contraction force and contribute to a raise of the sustained level of trapezius muscle activity. The current study specifically clarifies the validity of the relationship between ciliary-muscle contraction force and trapezius muscle activity and demonstrates that this relationship is not due to a general personality trait. We conclude that a high level of ciliary muscle contraction force can contribute to a development of musculoskeletal complaints in the neck-shoulder area.

Corrigendum: Prefrontal Cortex Oxygenation Evoked by Convergence Load Under Conflicting Stimulus-to-Accommodation and Stimulus-to-Vergence Eye-Movements Measured by NIRS.

[This corrects the article DOI: 10.3389/fnhum.2018.00298.].

Prefrontal Cortex Oxygenation Evoked by Convergence Load Under Conflicting Stimulus-to-Accommodation and Stimulus-to-Vergence Eye-Movements Measured by NIRS.

Purpose: To extend our knowledge of the functional linkages between visual fatigue and regional cerebral prefrontal cortex (PFC) oxygenation, we measured time related hemodynamic changes over the right dorsolateral prefrontal cortex (dlPFC) during convergence load under conflicting stimulus-to-accommodation and stimulus-to-vergence eye movements with and without concurrent mental load. Methods: Twenty healthy participants with a median age of 28 years (range: 18-44 years) fixated upon a vertical bar presented separately to the left and right eyes, using polarized filters, during four counterbalanced 10-min periods: (i) no accommodation/vergence conflict (Control, Ctrl); (ii) added convergence load and accommodation/vergence conflict (Conv); (iii) added cognitive load only (Cog) and; (iv) a combination of added cognitive and convergence load and accommodation/vergence conflict (Cc). Viewing distance was 65 cm. Non-invasive measurements of hemodynamic activity over the dlPFC were quantified by functional near-infrared spectroscopy (fNIRS). During the two-convergence load conditions, the horizontal disparity of the two bars varied dynamically from no disparity to a disparity set 20% below the individual threshold for diplopia. Cognitive load was induced by the n-back-2 test which required the subject to memorize and recall the changing colors of the horizontal bars and decide when a given color was the same as that occurring two colors previously. fNIRS data were averaged over 10-s windows centered at 0, 2, 4, 6, 8, and 10 min of each task, subtracted from a 20-s baseline window immediately preceding the visual task, and then represented as changes in oxygenated hemoglobin (ΔHbO2), deoxygenated hemoglobin (ΔHHb) and total hemoglobin (ΔtHb). Results: Linear mixed model analyses showed that hemodynamic activity was systematically influenced by time (p < 0.001). The group-averaged time-related level of change across the viewing conditions did not differ when compared with one another (p > 0.05). Larger convergence eye-movement responses under conflicting stimulus-to-accommodation, and stimulus-to-vergence over time, increased ΔHbO2 and ΔtHb only in condition Cc and after 8 min of task time (p < 0.10 for min-6 and min-8: p < 0.05 for min-10). Discussion: Collectively, our data suggest that HbO2, HHb, and tHb, recorded over the dlPFC with fNIRS, can be used to assay the degree to which supervisory oculomotor control processes are activated during visually deficient near work.

Computer vision syndrome: A review.

BACKGROUND: Computer vision syndrome (CVS) is a collection of symptoms related to prolonged work at a computer display. OBJECTIVE: This article reviews the current knowledge about the symptoms, related factors and treatment modalities for CVS. METHODS: Relevant literature on CVS published during the past 65 years was analyzed. RESULTS: Symptoms reported by computer users are classified into internal ocular symptoms (strain and ache), external ocular symptoms (dryness, irritation, burning), visual symptoms (blur, double vision) and musculoskeletal symptoms (neck and shoulder pain). The major factors associated with CVS are either environmental (improper lighting, display position and viewing distance) and/or dependent on the user's visual abilities (uncorrected refractive error, oculomotor disorders and tear film abnormalities). CONCLUSION: Although the factors associated with CVS have been identified the physiological mechanisms that underlie CVS are not completely understood. Additionally, advances in technology have led to the increased use of hand-held devices, which might impose somewhat different visual challenges compared to desktop displays. Further research is required to better understand the physiological mechanisms underlying CVS and symptoms associated with the use of hand-held and stereoscopic displays.

Good expert knowledge, small scope.

BACKGROUND: During many years of occupational stress research, mostly within the German governmental program for "Humanization of Work Life'', remarkable deficits concerning visual work were seen, the most striking being the lack of cooperation between the different experts. OBJECTIVE: With regard to this article hard arguments and ideas for solutions had to be found. METHODS/PARTICIPANTS: A pilot study in 21 enterprises was realized (1602 employees with different visual work tasks). A test set of screening parameters (visual acuity, refraction, phoria, binocular cooperation and efficiency, accommodation range and color vision) were measured. The glasses and/or contact lenses worn were registered and the visual tasks analyzed. In work at visual display units (VDU) the eye movements were recorded and standardized questionnaires were given (health, stress, visual work situation). Because of the heterogeneity of the sample only simple statistics were applied: in groups of different visual work the complaints, symptoms, hassles and uplifts were clustered (SAS software) and correlated with the results of the visual tests. Later a special project in 8 companies (676 employees) was carried out. The results were published in [14]. RESULTS: Discomfort and asthenopic symptoms could be seen as an interaction of the combination of tasks and working conditions with the clusters of individual functionalisms, frequently originating in postural compromises. Mainly three causes for stress could be identified: 1. demands inadequate with regard to intensity, resolution, amount and/or time structure; 2. prevention of elementary perceptive needs; 3. entire use of partial capacities of the visual organ. Symptoms also were correlated with heteronomy. Other findings: influence of adaptation/accommodation ratio, the distracting role of attractors, especially in multitasking jobs; influence of high luminance differences. Dry eyes were very common, they could be attributed to a high screen position, low light, monotonous tasks and office climate. For some parameters a diurnal rhythm could be identified. Nowhere special programs for ageing employees were found: the right glasses; retinal problems and signs of destabilization of vision. CONCLUSIONS: In all enterprises, the ergophthalmological and visual ergonomic knowledge of the occupational physicians was poor, visual ergonomists were not available and there was only very poor cooperation with ophthalmologists and optometrists, the first of whom additionally had not much knowledge of modern work.

Forging partnerships between optometrists and ergonomists to improve visual comfort and productivity in the workplace.

Ergonomists and optometrists often have mutual clients/patients with complex visual needs in the workplace but communication between the professionals is usually indirect through the client/patient. This paper describes a joint professional development meeting between optometrists and ergonomists in Canberra, Australia, which included a discussion to explore how to improve communication between the two professions. Optometrists and ergonomists reported they would prefer more information before conducting assessments and providing advice. Vision screening forms commonly in use for computer workers were viewed as inadequate to meet these needs. Communication between the two professions was hampered by absence of contact details of the optometrist/ergonomist, perceptions that the other profession is too busy to talk, privacy considerations in sharing information and funding issues for shared care arrangements. There are opportunities for increasing awareness of good vision in workplaces. Communication between optometrists and ergonomists can be improved by developing information-sharing documents relevant to modern workplaces.

Setting visual pre-placement testing in a technology manufacturing environment.

Every day we use our eyes to perform activities of daily living and work. Aging changes as well as health conditions can impact an individual's visual function, making it more difficult to accurately perform work activities. Occupational therapists work closely with optometrists and employers to develop ways to accommodate for these changes so that the employee can continue to perform the work tasks. This manuscript outlines a case study of systematically developing visual demands analyses and pre-placement vision screening assessment protocols for individuals completing quality inspection positions. When the vision screening was completed, it was discovered that over 20% of the employees had visual deficits that were correctable. This screening process yielded improved quality results but also identification of previously undetected visual deficits. Further development of vision screening in the workplace is supported.

Neck pain brought into focus.

A time honored dictum states that the eyes "lead the body", i.e., that the body typically adjusts its position to compensate for an impoverished retinal image (e.g., as due to optical blur, and/or inappropriately sized visual target). But only moderate or low level of evidence exists in support of this view. Inconclusive evidence does not, however, equal negative evidence. The accommodation/vergence system does exhibit signs of overload in contemporary working life, including eye discomfort, transient myopia, altered pattern of eye-lens oscillations, and associated phoria. Accommodation/vergence overload, caused by non-ergonomic near work, may also emerge as quickly as within one regular workday. Long-term musculoskeletal consequences of high accommodation/vergence demands have nevertheless not yet been studied in any detail. A research agenda which aims to provide multi-scientific evidence for eye-neck/shoulder interactions with public health implications and which also, in addition, study the eye-neck/shoulder mechanisms and elucidates the operating characteristics, should consequently be highly warranted. This new knowledge would be useful for physiotherapists, ergonomists and opticians, who in their profession treat patients experiencing vision- and musculoskeletal disorders. If both visual and the musculoskeletal aspects are given full and equal weight in the design and evaluation of work places, it is predicted to lead to an improved quality of life for the individual worker, and an enhanced productivity for the employer.

Optimal correction in spectacles: intervention effects on eyestrain and musculoskeletal discomfort among postal workers.

BACKGROUND: The static posture of postal workers when sorting mail can lead to musculoskeletal discomfort. Research has shown a connection between eyestrain and upper-body musculoskeletal discomfort in general, including postal workers. A previous study of postal workers found that most of those with eye strain were in need of a new correction in their existing spectacles. OBJECTIVE: Evaluate intervention effects on eyestrain and musculoskeletal discomfort with new spectacles for postal workers. METHODS: Postal workers subjectively reported eyestrain, musculoskeletal discomfort and their opinions of the visual environment via questionnaires pre- and post-intervention. After an eye examination the postal workers were divided into two groups: those who needed new spectacles and those who did not. RESULTS: Those who needed new spectacles showed a higher prevalence of eyestrain and musculoskeletal discomfort pre-intervention. Post-intervention, the postal workers rated their vision better and the average eyestrain and musculoskeletal discomfort decreased for both groups. These workers also experienced a decrease in discomfort on the left (static) side of the neck while sorting mail. CONCLUSION: An intervention providing the optimal correction reduces eyestrain and decreases musculoskeletal discomfort, especially from the neck.

Risk factors, incidence and persistence of symptoms from the eyes among professional computer users.

BACKGROUND: Symptoms from the eyes are common among computer users. Knowledge is scarce about these problems, however. OBJECTIVES: The aim was to study risk-factors, incidence and persistence of eye-symptoms among professionally active computer users. METHODS: This was a questionnaire based prospective study where 1283 males and females from different professions and companies answered a baseline questionnaire about individual factors and working conditions, e.g. duration of daily computer work, comfort of screen work, psychosocial factors. Subjects were at baseline and 10 follow-ups asked about the number of days with eye-symptoms during the preceding month. RESULTS: The incidence-rate of symptoms persisting minimum three days was 0.38/person-year. A multivariate Hazard-ratio model showed significant associations with extended continuous computer work, tasks with high demands on eye-hand coordination, low level of control, visual discomfort, female sex and nicotine use. Eye-symptoms at baseline was a strong risk factor for new symptoms. CONCLUSION: The incidence of eye-symptoms among professional computer users is high and related to both individual and work-related factors. The organization of computer work should secure frequent breaks from near-work at the computer screen. The severity of vision-related problems could in field studies be quantified by asking for the persistence of symptoms.

Effects of visually demanding near work on trapezius muscle activity.

Poor visual ergonomics is associated with visual and neck/shoulder discomfort, but the relation between visual demands and neck/shoulder muscle activity is unclear. The aims of this study were to investigate whether trapezius muscle activity was affected by: (i) eye-lens accommodation; (ii) incongruence between accommodation and convergence; and (iii) presence of neck/shoulder discomfort. Sixty-six participants (33 controls and 33 with neck pain) performed visually demanding near work under four different trial-lens conditions. Results showed that eye-lens accommodation per se did not affect trapezius muscle activity significantly. However, when incongruence between accommodation and convergence was present, a significant positive relationship between eye-lens accommodation and trapezius muscle activity was found. There were no significant group-differences. It was concluded that incongruence between accommodation and convergence is an important factor in the relation between visually demanding near work and trapezius muscle activity. The relatively low demands on accommodation and convergence in the present study imply that visually demanding near work may contribute to increased muscle activity, and over time to the development of near work related neck/shoulder discomfort.