Digital eye strain:Prevalence, measurement and amelioration

Digital device usage has increased substantially in recent years across all age groups, so that extensive daily use for both social and professional purposes is now normal. Digital eye strain (DES), also known as computer vision syndrome, encompasses a range of ocular and visual symptoms, and estimates suggest its prevalence may be 50% or more among computer users. Symptoms fall into two main categories: those linked to accommodative or binocular vision stress, and external symptoms linked to dry eye. Although symptoms are typically transient, they may be frequent and persistent, and have an economic impact when vocational computer users are affected. DES may be identified and measured using one of several available questionnaires, or objective evaluations of parameters such as critical flicker–fusion frequency, blink rate and completeness, accommodative function and pupil characteristics may be used to provide indices of visual fatigue. Correlations between objective and subjective measures are not always apparent. A range of management approaches exist for DES including correction of refractive error and/or presbyopia, management of dry eye, incorporating regular screen breaks and consideration of vergence and accommodative problems. Recently, several authors have explored the putative role of blue light-filtering spectacle lenses on treating DES, with mixed results. Given the high prevalence of DES and near-universal use of digital devices, it is essential that eye care practitioners are able to provide advice and management options based on quality research evidence

How visual ergonomics interventions influence health and performance - with an emphasis on non-computer work tasks

Visual ergonomics evaluations and interventions were performed on non-computer work tasks at recycling facilities, post sorting facilities and operating theatres. The results can to some extent be applicable to other professions and workplaces. The purpose of the research was to investigate the effects of visual ergonomics interventions on eyestrain, musculoskeletal discomfort, headache, and visual performance at work. Individuals with eyestrain reported more musculoskeletal discomfort than individuals without eyestrain. Factors shown to have an impact on eyestrain and musculoskeletal discomfort were the visual environment, the individual’s perceived visual ability and need for spectacles. Such findings have been reported among computer users. The results presented here show that non-computer work tasks may induce similar findings as well. Evaluations of workplaces and interventions with lighting and spectacles were performed in the studies presented in this thesis. The interventions were evaluated by direct observations such as an expert approach and by indirect observations by means of questionnaires. After the evaluation and measurement of the lighting at the recycling facilities, a number of lighting recommendations were suggested to increase visibility and reduce accident risks. For the younger postal workers in particular, better lighting reduced eyestrain and musculoskeletal discomfort. Pre-intervention, the individuals with eyestrain had lower productivity than those without; their productivity increased with better lighting. The musculoskeletal discomfort from the neck decreased especially from the static side for the postal workers after they were provided with correct power in their spectacles. It is possible to improve the work posture of presbyopic postal workers with customised sorting spectacles, in particular because using the sorting spectacles results in a decrease of the backward tilt of the head. In visually demanding work such as surgery, the luminance contrast within the visual field is essential. This is especially the case for the scrub nurse who has to look into the very bright operating light and also see the less highly lit instrument table and other important aspects in the operating room. The visual focus of the surgeons is in the operating cavity, and their eyes are completely adjusted to that level. It can take up to two minutes before their vision is fully functioning again after being exposed to the high illuminance from the operating cavity. This poses a risk if something happens in the operating room outside the operating cavity that requires good visibility from the surgeon. It is thus vital to increase the general lighting in an operating room, especially around the operating table, to decrease the luminance contrasts and facilitate the operating personnel’s visual ability. In this intervention study, the operating personnel rated the improved lighting as improving their perceived visual ability and a decreasing tiredness. All together, the studies show that visual ergonomics is a multidisciplinary science that requires a holistic approach. This thesis will hopefully contribute to increasing the awareness of the effects of a good visual environment and its benefits for the individual’s health

Effects of glare on binocular vision and reading behaviour performing computer work

We spend more and more time working with computers. When we do so our central visual field lacks three-dimensional (3D) features and this leads to reduced binocular control and may result in eye-related symptoms. When other factors such as direct and indirect glare are added to a computer work situation further stress is placed on the visual system and binocular control may be even further reduced and our reading behaviour may also be influenced. These factors are likely to contribute to the vision- and eye symptoms referred to collectively as computer vision syndrome (CVS). Three areas of clinical study are included in the context of using a computer screen for demanding near visual tasks. This research aimed to explore the theoretical relationship between: (1) the importance of centrally placed 3D features in respect to accommodation and vergence mechanisms; (2) the influence of degraded stimuli and/or degraded retinal image on the quality of binocular vision as an indicator of visual fatigue; (3) the influence of degraded stimuli and/or degraded retinal image on eye movements when reading. Paper I clarified the importance of implementing centrally placed 3D fixation stimuli to contribute to increase vergence accuracy and fixation stability. Paper II evaluated the influence of disability glare on binocular coordination. The results indicated that binocular coordination increased in instability with the severity of glare and there was a more pronounced effect when lighting condition created direct glare. Paper III described the influence of disability glare on eye movements when reading. It is clear that these eye movements were negatively affected in the direct- and indirect glare lighting conditions. Paper IV evaluated the threshold luminance of direct glare using a subjective response regarding eye symptoms in addition to an evaluation of the effect on binocular coordination as a benchmark. Direct glare of 2000 cd/m2 was found to decrease the instability of binocular coordination with an increased level of eye pain. In conclusion, these findings argue for a more pronounced relationship between reduced cues of centrally placed 3D features when working with computers with elevated exposure to disability glare. Direct glare appears to degrade the visibility of the retinal image to such a high degree that it can be identified as the most pronounced inappropriate lighting condition. Evaluation of the luminance threshold of direct glare suggests that it reasonable to recommend that stray light toward the eyes should be significantly lower than 2000 cd/m2. This research has taken a step in the direction of justifying the importance of following lighting design recommendations in computer work environments

A reliable and valid questionnaire was developed to measure computer vision syndrome at the workplace

Objectives: To design and validate a questionnaire to measure visual symptoms related to exposure to computers in the workplace. Study Design and Setting: Our computer vision syndrome questionnaire (CVS-Q) was based on a literature review and validated through discussion with experts and performance of a pretest, pilot test, and retest. Content validity was evaluated by occupational health, optometry, and ophthalmology experts. Rasch analysis was used in the psychometric evaluation of the questionnaire. Criterion validity was determined by calculating the sensitivity and specificity, receiver operator characteristic curve, and cutoff point. Testeretest repeatability was tested using the intraclass correlation coefficient (ICC) and concordance by Cohen’s kappa (k). Results: The CVS-Q was developed with wide consensus among experts and was well accepted by the target group. It assesses the frequency and intensity of 16 symptoms using a single rating scale (symptom severity) that fits the Rasch rating scale model well. The questionnaire has sensitivity and specificity over 70% and achieved good testeretest repeatability both for the scores obtained [ICC 5 0.802; 95% confidence interval (CI): 0.673, 0.884] and CVS classification (k 5 0.612; 95% CI: 0.384, 0.839). Conclusion: The CVS-Q has acceptable psychometric properties, making it a valid and reliable tool to control the visual health of computer workers, and can potentially be used in clinical trials and outcome research.This study was supported by the Spanish National Institute for Occupational Safety and Health (INSHT) (Grant number: 07/606). Project reference: UAL/PVDVIS

Digital Eye Strain: Investigation and Optometric Management

Digital eye strain (DES) is a condition encompassing visual and ocular symptoms that may arise due to the prolonged use of digital devices. The 2023 Tear Film Ocular Surface Lifestyle report defined DES as “the development or exacerbation of recurrent ocular symptoms and / or signs related specifically to digital device screen viewing”. Studies vary as to the prevalence of DES with some reporting values as low as 10 % and some reporting values over 90 %. This programme of research was centred around the identification and management of DES with a focus on Ireland and the UK. The attitudes of optometrists to DES were investigated. Optometrists considered DES to be a significant issue and one that they felt confident in dealing with. Optometrists typically underestimated the prevalence of DES (median at 25 %) compared to previous reports in the literature. Advising on frequent breaks, ocular lubricants and workstation / device set up were the most important management considerations. There were mixed views on specialist spectacle lenses for DES, particularly ‘blue filtering’ designs, although a significant proportion (34.7 %) did indicate that they recommended these. DES in working age adults in Ireland and the UK was examined for the first time. Using the Computer Vision Syndrome Questionnaire (CVS-Q), 62.6 % of participants were classified as DES sufferers. There was a very weak correlation between hours of device use and having CVS-Q ≥6 (rs=0.155, rs 2=0.024, p=0.001). Fewer than 10 % reported that symptoms were so bad that they affected their work. Given the increase in digital device use in older adults (≥60 years), this programme of research examined the syndrome in this age cohort for the first time. In a cohort drawn from community optometry practice, significant daily durations of device use were found (median 4 hours) and 51.6 % were found to have DES. There was a strong correlation (rs=0.81, rs 2=0.6561, p<0.00001) between dry eye symptoms and DES. The test-retest repeatability of the CVS-Q in an older population was found to be good and a minimum clinically important difference of 1.96 was determined

Real-Time Non-Intrusive Assessment of Viewing Distance During Computer Use

Purpose: To develop and test the sensitivity of an ultrasound-based sensor to assess the viewing distance of visual display terminals operators in real-time conditions. Methods: A modified ultrasound sensor was attached to a computer display to assess viewing distance in real time. Sensor functionality was tested on a sample of 20 healthy participants while they conducted four 10-minute randomly presented typical computer tasks (a match-three puzzle game, a video documentary, a task requiring participants to complete a series of sentences, and a predefined internet search). Results: The ultrasound sensor offered good measurement repeatability. Game, text completion, and web search tasks were conducted at shorter viewing distances (54.4 cm [95% CI 51.3-57.5 cm], 54.5 cm [95% CI 51.1-58.0 cm], and 54.5 cm [95% CI 51.4-57.7 cm], respectively) than the video task (62.3 cm [95% CI 58.9-65.7 cm]). Statistically significant differences were found between the video task and the other three tasks (all p < 0.05). Range of viewing distances (from 22 to 27 cm) was similar for all tasks (F = 0.996; p = 0.413). Conclusions: Real-time assessment of the viewing distance of computer users with a non-intrusive ultrasonic device disclosed a task-dependent pattern. (C) 2016 American Academy of OptometryPostprint (author's final draft

Musculoskeletal disorders in demanding computer work - with air traffic control as a model

In computer work, musculoskeletal disorders are frequently reported, but the knowledge about causal relationships is limited. In air traffic control, female and male operators perform exactly the same computer work. Introduction of a new computer system implied a momentary change from a “varied” system containing different in-put devices, to a system characterized by intensive mouse-work. The effect of the change on the physical exposure was studied, as well as the musculoskeletal health before and after the change. In addition, gender differences and psychosocial factors were assessed. The physical workload, recorded in 14 subjects in both systems by technical measurements of postures, movements and muscular load, showed large differences: The mouse-intensive system was associated with lower movement velocities, less varying postures and less rest in the right forearm extensor muscles. The differences were amplified at high work intensity. Neck postures in females with neck/shoulders/upper back disorders were compared to those in healthy referents, but without significant differences. Musculoskeletal disorders in neck and upper limbs were assessed by standardised physical examinations in 148 air traffic controllers (71 women and 77 men) and the psychosocial work environment by questionnaire. Disorders in elbows/hands increased significantly after 20 months of work in the mouse-intensive system, while in neck/shoulders/upper back, there was no consistent change. There was no gender difference in elbows/hands disorders, while the females were at higher risk in neck/shoulders/upper back. Disorders in elbows/hands were not explained by psychosocial factors. Most likely, these findings are applicable to similar technological developments in other settings

Optometric management of video display terminal related vision problems

The growth of the digital market is progressively leaving a big impact on eye care professionals’ practice, whose rule is to permit a comfortable vision to their patients. Video display terminal related vision problems have drawn a particular attention, since the number of computer workers have increased over the last years. The popularity of smaller digital devices, such as smart phones and tablets, is increasing also among younger generations, as almost every child own one by the start of elementary school. Computers have also become an irreplaceable accessory, when talking about students in higher education institutes. The main objective of the thesis is to analyse Computer Vision Syndrome along with other vision related problems induced by other digital devices and a proper management of those. To alleviate the symptoms and to provide a comfortable vision, while using digital screens for several hours, optometrists have a wide selection of different treatment methods. Various researches, that approve better visual performance after the consultation with an eye care professional, have been studied. Prevention, including a proper positioning of the computer workstation or ergonomic mobile phone and tablet use, plays a significant rule. However, in the presence of the symptoms, depending on the nature of those, different approaches should be considered; the most common solutions to combat CVS are correction of refraction error, binocular and accommodative dysfunction, decreasing the amount of blue light entering the eye and dry eye management. Since the rapidly digitized world is changing people’s behaviour, the visual demands required for operating modern technology will continue to increase