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Flickering patterns that shift in chromaticity can be uncomfortable and may trigger epileptic seizures, though the underlying factors are not fully understood. In the spatial domain, chromatic contrast in images is a potential predictor of visual discomfort, with higher contrast generally leading to increased discomfort. This study investigated whether chromatic contrast between two flickering colors in a uniform field influences discomfort. Participants rated their subjective discomfort for various flickering color combinations defined by the CIE L*a*b* uniform color space. Overall, discomfort increased with both chromatic and brightness contrasts. Additionally, flickers containing highly saturated red generally caused greater discomfort compared to those without red, an effect not observed with low saturation. Our findings suggest that visual discomfort induced by time-varying chromatic patterns is partly influenced by chromatic contrast over time. Furthermore, unlike the spatial domain, discomfort in the temporal domain may be specifically associated with the hue of red., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Purpose: Smartphones are the most frequently used digital devices globally with ~6.80 billion users. Despite the ubiquitous use of smartphones, limited information is known on the preferred viewing distance and font size of smartphone users. This study investigated viewing distance, font size and symptoms of eyestrain in non-presbyopic and presbyopic smartphone users., Methods: In this quantitative research study, viewing distance and font size were measured in a group of non-presbyopes (n = 107) and presbyopes (n = 53), whilst participants viewed a text message and a web page on their own smartphone. Subjects also responded to a verbal questionnaire related to the characteristics of their smartphone and the computer vision syndrome questionnaire to assess symptoms of eyestrain. Data were analysed using descriptive and inferential statistics., Results: For the total sample, the mean viewing distance for a text message was 37.13 ± 8.82 cm (median 36.00 cm), and for a web page was 36.11 ± 7.98 cm (median 36.00 cm). Presbyopes had longer median viewing distances compared with non-presbyopes for a text message (41 cm vs. 34 cm, p < 0.001) and web page (40 cm vs. 34 cm, p < 0.001). The font size for non-presbyopes were <1.0 M whilst for presbyopes were >1.2 M. More than twice the percentage of non-presbyopes were classified with digital eyestrain (DES) compared with presbyopes., Conclusions: Non-presbyopes used shorter viewing distances, smaller font sizes and were more predisposed to DES than presbyopes. The viewing distances adopted by presbyopes were similar to the conventional near-working distance of 40 cm. Eye care practitioners should consider viewing distances when assessing near-visual functions and prescribing a near refractive correction, particularly in non-presbyopes. There should be greater awareness of the importance of adopting appropriate viewing distances when using smartphones., (© 2024 The Author(s). Ophthalmic and Physiological Optics published by John Wiley & Sons Ltd on behalf of College of Optometrists.)

With the development of brain-computer interface industry, large amounts of related applications have entered people's vision. BCI applications based on steady-state visual evoked potentials (SSVEP) are widely used because they do not require pre-training and have high information transmission rates. However, in the actual use of SSVEP stimulus paradigm, the subjects will produce visual fatigue with the use, and fatigue will affect the transmission efficiency. In this experiment, an experimental environment consisting of two paradigm stimulus frequencies (7.5 Hz, 15 Hz), three resolutions (800 × 600, 1280 × 720, 1920 × 1080) and three refresh rates (120 Hz, 240 Hz, 360 Hz) is set up. The Likert scale is used to collect subjective fatigue and preference scores, and the EEG acquisition system and eye tracker are used to collect objective data. Using the proposed information entropy-CRITIC algorithm to combine subjective and objective indicators, a fatigue assessment system (display screen fitness-DSF) is innovated to score different experimental environments. The higher the DSF score, the better the visual experience. The results show that when using the 7.5 Hz SSVEP paradigm, the combination of 360 Hz and 1920 × 1080 can bring the best visual experience. When using the 15 Hz SSVEP paradigm, the combination of 240 Hz and 1280 × 720 is the best. DSF provides powerful help for hardware and software selection guidance and vision protection when using SSVEP-based BCI applications., Competing Interests: Declarations Competing interests The authors declare no competing interests. Institutional review board statement The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of Xi’an Jiaotong University, China (No. 2023 − 1552). Informed consent was obtained from all subjects involved in the study., (© 2024. The Author(s).)

Background: This study aims to explore the impact of using visual display terminal (VDT) on the visual fatigue of operators through meta-analysis., Methods: The terms "VDT", "visual fatigue", "eyestrain", and "viewing distance" were selected from the Wangfang, China National Knowledge Infrastructure (CNKI), Web of Science, Springer, and Science Direct online databases. The retrieval time was from the establishment of the database to the present. All clinical studies related to the analysis of the effects of VDT use on visual fatigue were available. The included studies were screened, and after quality assessment, basic data and outcome index data were extracted. The count data were represented by relative risk (RR) and 95% confidence interval (CI). The measurement data were represented by the mean value (MD), standard deviation (SD), and 95% CI. Review Manager 5.3 (RevMan5.3) was employed to analyze the included indicators. Funnel plots were drawn using RevMan5.3 to analyze potential publication bias. The incidence of visual fatigue, lens use time, blink interval, and other indicators were compared between the VDT group and the control (Ctrl) group. Meanwhile, the incidence of eye fatigue and blurred vision in the two groups was counted., Result: The incidence of eye pain, fatigue, blurred vision, teary eyes, and dry eyes in the VDT group significantly exceeded that in the Ctrl group. Meanwhile, the dry eye score, as well as the scores for eye fatigue, discomfort, and blurred vision, were significantly higher in the VDT group compared to the Ctrl group., Conclusions: The results indicate that the use of VDT has a significant impact on visual fatigue., (© 2024. The Author(s).)

Animated films are highly popular in society, particularly among children and adolescents. During film production, selecting an adequate colour palette and scene dynamism is crucial for creating a visual impact on the audience. However, the influence of visual aesthetics, such as colour and scene dynamism on visual fatigue remains unexplored. In the present study, visual fatigue was assessed and compared in 30 young participants after viewing two popular films: Spider-Man: Across the Spider-Verse, an active, fast-paced film, and My Neighbour Totoro, a more relaxed film. Both films were viewed twice, once with the original colour palette and once in greyscale. Watching Spider-Man film induced a greater degree of visual fatigue than My Neighbour Totoro in two subjective questionnaires evaluating visual fatigue, and in the vergence facility and binocular accommodative facility tests. Moreover, important differences in the visual dynamics and colour aspects between both films were found. These results demonstrate that the high-paced and high-colour aspects of films directly affect visual fatigue. Future animated film producers should consider these factors that are relevant to their audiences., (© 2024. The Author(s).)

The usage of smart glasses in goods logistics and order picking has mainly been studied through cross-sectional experimental studies. Our longitudinal field study investigated the effects of smart glasses on the eyesight of 43 employees at two German companies. We combined ophthalmological examinations and questionnaire surveys at two points in time, six months apart. The vision of the employees was examined before and after each work shift. Mixed effects logistic regression was conducted to determine the associations between smart glasses use and effects on visual acuity. In the baseline examination, differences in eyesight before and after shifts were small and not statistically significant. However, some individuals experienced deteriorations, especially in visual acuity at near distances ( n = 7 for the right eye, n = 6 for the left). Participants over 40 years of age had 16.1 times higher odds of deterioration compared to those under 40 years (95% CI: 2.7-95.9, p = 0.002). The most commonly reported eye strains were eye fatigue ( n = 32), rubbing ( n = 25), and burning ( n = 24). If smart glasses are to be implemented in logistics companies, it is recommended to offer employees eye tests with an industrial physician in advance.

Purpose: Asthenopia is related to near vision activities or visual tasks that dissociate accommodation from vergence. Since the results of previous studies using objective measures to diagnose asthenopia are inconsistent, this study compared optometric tests and objective metrics of accommodation in non-asthenopic and asthenopic young adults before and after a visual fatigue task., Methods: The accommodative response was recorded objectively for 6 min at a 3.33 D accommodative demand using an autorefractor, before and after a 5-min non-congruent visual task. Accommodation was disassociated from vergence with a ±2.00 D accommodative flipper while reading at the same distance. Optometric tests and subjective evaluations of asthenopia were performed before and after the task. Twenty-six non-presbyopic adults (23.15 ± 2.56 years) were included and identified as asthenopic (n = 14) or non-asthenopic (n = 12) based on their score on the Computer Vision Syndrome Questionnaire., Results: A mixed ANOVA found no significant difference between the groups for objective (accommodative response) or subjective metrics (feeling of fatigue, optometric tests), although all participants reported greater visual fatigue after the task. A significant effect of time (before and after the non-congruent task) was identified for the overall sample for mean accommodative lag (+0.10 D, p = 0.01), subjective visual fatigue (+1.18, p < 0.01), negative relative accommodation (-0.20 D, p = 0.02) and near negative fusional reserve (blur: +2.46Δ, p < 0.01; break: +1.89Δ, p < 0.01; recovery: +3.34Δ, p = 0.02)., Conclusions: The task-induced asthenopia, measured both objectively and subjectively, was accompanied by a change in accommodative lag, greater visual fatigue and a decrease in negative relative accommodation. Conversely, near negative fusional reserves seem to adapt to the task. No significant differences were found between the two groups with respect to accommodative metrics (objective) or subjective and optometric tests., (© 2024 College of Optometrists.)

Background: Aniseikonia is a binocular vision disorder that has been associated with asthenopic symptoms. However, asthenopia has been evaluated with subjective tests that make difficult to determine the level of aniseikonia. This study aims to objectively evaluate the impact of induced aniseikonia at different levels on visual fatigue by measuring the orbicularis oculi muscle activity in the dominant and non-dominant eyes while performing a reading task., Methods: Twenty-four collegiate students (24.00 ± 3.86 years) participated in this study. Participants read a passage for 7 minutes under four degrees of aniseikonia (0%, 3%, 5% and 10%) at 50 cm. Orbicularis oculi muscle activity of the dominant and non-dominant eye was recorded by surface electromyography. In addition, visual discomfort was assessed after each task by completing a questionnaire., Results: Orbicularis oculi muscle activity increased under induced aniseikonia ( i.e. , greater values for the 10% condition in comparison to 0%, and 3% conditions ( p  = 0.034 and p  = 0.023, respectively)). No statistically significant differences were observed in orbicularis oculi muscle activity for the time on task and between the dominant and non-dominant eyes. Additionally, higher levels of subjective visual discomfort were observed for lower degrees of induced aniseikonia., Conclusion: Induced aniseikonia increases visual fatigue at high aniseikonia degrees as measured by the orbicularis oculi muscle activity, and at low degrees as measured with subjective questionnaires. These findings may be of relevance to better understand the visual symptomatology of aniseikonia., Competing Interests: Beatriz Redondo and Jesús Vera are Academic Editors for PeerJ., (©2024 Redondo et al.)

In code-modulated visual evoked potential (c-VEP) based BCI systems, flickering visual stimuli may result in visual fatigue. Thus, we introduced a discrete-interval binary sequence (DIBS) as visual stimulus modulation, with its power spectrum optimized to emphasize high-frequency components (40 Hz-60 Hz). 8 and 17 subjects participated, respectively, in offline and online experiments on a 4-target asynchronous c-VEP-based BCI system designed to realize a high positive predictive value (PPV), a low false positive rate (FPR) during idle states, and a high true positive rate (TPR) in control states, while minimizing visual fatigue level. Two visual stimuli modulations were introduced and compared: a maximum length sequence (m-sequence) and the high-frequency discrete-interval binary sequence (DIBS). The decoding algorithm was compared among the canonical correlation analysis (CCA), the task-related component analysis (TRCA), and two approaches of sub-band component weight calculation (the traditional method and the proportional method) for FBCCA and FBTRCA. In the online experiments, the average PPV, FPR and TPR achieved, respectively [Formula: see text], [Formula: see text], [Formula: see text] with m-sequence, while [Formula: see text], [Formula: see text] and [Formula: see text] with DIBS. Estimated by objective eye-related metrics and a subjective questionnaire, the visual fatigue in DIBS cases is significantly smaller than that in m-sequence cases. In this study, the feasibility of a novel modulation approach for visual fatigue reduction was proved in an asynchronous c-VEP system, while maintaining comparable performance to existing methods, which provides further insights towards enhancing this field's long-term viability and user-friendliness.

Stereoscopic visual fatigue (SVF) due to prolonged immersion in the virtual environment can lead to negative user experience, thus hindering the development of virtual reality (VR) industry. Previous studies have focused on investigating the evaluation indicators associated with SVF, while few studies have been conducted to reveal the underlying neural mechanism, especially in VR applications. In this paper, a modified Go/NoGo paradigm was adopted to induce SVF in VR environment with Go trials for maintaining participants' attention and NoGo trials for investigating the neural effects under SVF. Random dot stereograms (RDSs) with 11 disparities were presented to evoke the depth-related visual evoked potentials (DVEPs) during 64-channel EEG recordings. EEG datasets collected from 15 participants in NoGo trials were selected to conduct individual processing and group analysis, in which the characteristics of the DVEPs components for various fatigue degrees were compared and independent components were clustered to explore the original cortex areas related to SVF. Point-by-point permutation statistics revealed that DVEPs sample points from 230 ms to 280 ms (component P2) in most brain areas changed significantly when SVF increased. Additionally, independent component analysis (ICA) identified that component P2 which originated from posterior cingulate cortex and precuneus, was associated statistically with SVF. We believe that SVF is rather a conscious status concerning the changes of self-awareness or self-location awareness than the performance reduction of retinal image processing. Moreover, we suggest that indicators representing higher conscious state may be a better indicator for SVF evaluation in VR environments.

Purpose: Stereoscopic viewing has an impact on ocular dynamics, but its effects on accommodative functions are not fully understood, especially for autostereoscopic viewing. This study aimed to investigate the changes in dynamic accommodative response, accommodative amplitude, and accommodative facility of myopes after autostereoscopic visual training., Methods: We enrolled 46 adults (men = 22 and women = 24; age = 21.5 ± 2.5 [range = 18-25] years, spherical equivalent: -4.52 ± 1.89 [-8.88 to -1.75] diopters [D]) who visited the Eye & ENT Hospital of Fudan University. The study population was randomly divided into three-dimensional (3D) and two-dimensional (2D) viewing groups to watch an 11-minute training video displayed in 3D or 2D mode. Dynamic accommodative response, accommodative facility, and accommodative amplitude were measured before, during, and immediately after the training. Accommodative lag and the variability of accommodation were also analyzed. Visual fatigue was evaluated subjectively using a questionnaire., Results: Accommodative lag decreased from 0.54 ± 0.29 D to 0.42 ± 0.32 D (P = 0.004), whereas accommodative facility increased from 10.83 ± 4.55 cycles per minute (cpm) to 13.15 ± 5.25 cpm (P < 0.001) in the 3D group. In the 2D group, there was no significant change in the accommodative lag (P = 0.163) or facility (P = 0.975), but a decrease in accommodative amplitude was observed (from 13.88 ± 3.17 D to 12.71 ± 2.23 D, P = 0.013). In the 3D group, the accommodative response changed with the simulated target distance. Visual fatigue was relatively mild in both groups., Conclusions: The immediate impact of autostereoscopic training included a decrease in the accommodative lag and an increase in the accommodative facility. However, the long-term effects of autostereoscopic training require further exploration.

Significance: Digital display use has been accepted as a contributing factor to dry eye disease. Nowadays, plenty of new models of digital displays have been developed, and the differences in their nature and the ways in which they are set and used may contribute to differences in the eye-related problems they cause., Purpose: This study aimed to analyze the differences in ocular surface, tear film, and visual fatigue parameters after reading on different digital displays, with and without initial instillation of artificial tears., Methods: Thirty-one healthy individuals ranging in age from 20 to 26 years (mean ± standard deviation, 21.26 ± 1.73 years) were included in this prospective clinical study. Subjects' ocular surface, tear film, and visual fatigue parameters were assessed after reading for 15 minutes on a laptop computer, tablet, e-reader, and smartphone with matching characteristics and a baseline measurement. Measurements were taken with and without the instillation of artificial tears before the reading tasks and included the Ocular Surface Disease Index questionnaire, the Computer Vision Syndrome Questionnaire, tear meniscus height, the Schirmer I test, noninvasive keratograph break-up time, osmolarity, bulbar redness, and pupil size., Results: Statistically significant differences in the Ocular Surface Disease Index, Computer Vision the Syndrome Questionnaire, tear meniscus height, the Schirmer I test, noninvasive keratograph break-up time, osmolarity, and bulbar redness were obtained when comparing the displays (P < .05). Best results were obtained with the smartphone and the e-reader. Conversely, the computer produced the highest disturbance on the ocular surface and tear film. Finally, the instillation of artificial tears revealed no statistical improvement of ocular surface or tear film parameters for the same device (P > .05)., Conclusions: Taking into account the clinical tests for dry eye diagnosis, the smartphone may be considered as the least disturbing display, producing lower dry eye signs and symptoms in comparison with other devices.

Introduction: The prescription of blue-blocking (B-B) filters for the management of visual symptoms and signs associated with the use of electronic devices is routinely performed by eye care specialists. However, the utility of B-B filters is a matter of debate and discussion by the scientific community due to the lack of evidence supporting their use. Here, we aimed to determine the effects of using B-B filters on the dynamics of the accommodative response and pupil size and perceived levels of visual discomfort, while performing a 30-min reading task at a close distance in subjects who routinely use electronic devices., Methods: Nineteen healthy young adults (22.0 ± 2.7 years) read two 30-min passages on a computer screen placed at 50 cm, either while using a commercially available B-B filter or without any filter on two different days. The magnitude and variability of both the accommodative response and pupil size were dynamically measured for 60 s using the WAM-5500 open field autorefractometer at 4-5, 9-10, 14-15, 19-20, 24-25, and 29-30 min into the trial. The perceived levels of visual discomfort were also obtained., Results: The lag and variability of accommodation were insensitive to the blue light level (p = 0.34 and 0.62, respectively). There was a time-on-task effect for the variability of accommodation, showing greater instability over time regardless of the blue light level. The use of the B-B filter was associated with improved reading speed (p = 0.02), with an increase of 16.5 words per minute. However, it was not associated with any significant change in pupil dynamics or the perceived levels of visual discomfort (p> 0.05 in both cases)., Conclusions: Our data showed that the use of a B-B filter had no effect on accommodative dynamics or visual symptomatology. Based on these findings, there is no support for the prescription of B-B filters to attenuate the visual symptoms and signs associated with the use of electronic devices in healthy young adults., (© 2020 The Authors Ophthalmic & Physiological Optics © 2020 The College of Optometrists.)

Introduction: Digital eye strain (DES; computer vision syndrome) is a common cause of symptoms when viewing digital devices. Low-powered convex lenses (adds) have been recommended for the condition and "accommodative support" designs developed on this premise. The present research reports the extent to which dry eye is present in this population and the effect of convex lenses on symptoms and visual performance., Methods: The CVS-Q instrument was used to select pre-presbyopic adults with the symptoms of DES. Participants received a full eye examination including an assessment of dry eye with a modified SANDE questionnaire and using DEWS I criteria. The immediate effect of low-powered convex lenses (low adds: +0.50D, +0.75D, +1.25D) was investigated using subjective preference and a double-masked comparison with plano lenses with the Wilkins Rate of Reading Test (WRRT). Throughout this testing, participants wore their full distance refractive correction, based on non-cycloplegic retinoscopy and subjective refraction., Results: The signs and symptoms of dry eye were frequently present. Most participants reported a subjective preference for low adds, with +0.75D the most commonly preferred lens. Low adds (+0.50D and +0.75D; but not +1.25D) were associated with significantly improved performance at the WRRT. One quarter of participants read more than 10% faster with these additional convex lenses., Conclusions: The study population was aged 20-40y and mostly worked on desktop computers. It is possible that +1.25D add may be more advantageous for people who are older or work more at closer viewing distances. Many symptomatic users of digital devices report a preference for low adds and use of these lenses is often associated with an improvement in reading performance., (Copyright © 2020 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Computers have become to play an important role in people's lives throughout the world thus increasing the number of patients with ocular complaints. Also known as computer vision syndrome, accommodative asthenopia might be considered as a neglected occupational condition, but there is no consensus regarding diagnostic criteria, which leads to under-recognition and under-reporting. The aim of the study was to investigate the prevalence, early symptoms and specific preventive measures of accommodative asthenopia among computer-using medical students ( n  = 420), in a cross-sectional study. The most common early symptoms were: tired eyes/eye strain (86.1%), burning eyes (46.8%), migraines/headaches (46.8%), red-swollen eyes (43%), photophobia (41.8%), temporary blurred vision (35.4%), and eyelid spasms (32.9%). Our study identifies the most frequent early symptoms of accommodative asthenopia as a possible occupational disease, which might serve as a fundament for a future consensus strategy.

Background: Head-mounted displays (HMDs) and virtual reality (VR) have been frequently used in recent years, and a user's experience and computation efficiency could be assessed by mounting eye-trackers. However, in addition to visually induced motion sickness (VIMS), eye fatigue has increasingly emerged during and after the viewing experience, highlighting the necessity of quantitatively assessment of the detrimental effects. As no measurement method for the eye fatigue caused by HMDs has been widely accepted, we detected parameters related to optometry test. We proposed a novel computational approach for estimation of eye fatigue by providing various verifiable models., Results: We implemented three classifications and two regressions to investigate different feature sets, which led to present two valid assessment models for eye fatigue by employing blinking features and eye movement features with the ground truth of indicators for optometry test. Three graded results and one continuous result were provided by each model, respectively, which caused the whole result to be repeatable and comparable., Conclusion: We showed differences between VIMS and eye fatigue, and we also presented a new scheme to assess eye fatigue of HMDs users by analysis of parameters of the eye tracker.

In the visually challenging situation of microsurgery with many altered depth cues, digitalization of surgical systems disrupts two further depth cues, namely focus and parallax. Although in purely optical surgical systems accommodation and eye movements induce expected focus and parallax changes, they become statically fixed through digitalization. Our study evaluates the impact of static focus and parallax onto performance and subjective 3D perception. Subjects reported decreased depth realism under static parallax and focus. Thus surgeons’ depth perception is impacted further through digitalization of microsurgery, increasing the potential of artificial stereo-induced fatigue.

Smartphone and tablet use in Australia and worldwide is reaching saturation levels and associated visual and ocular discomfort such as headaches, eyestrain, dry eyes and sore eyes are widespread. This review synthesises the available literature and considers these symptoms in the context of a binocular vision and/or ocular surface aetiology. Eye discomfort with smartphones and tablets is discussed alongside similar symptoms reported with desktop computer use. Handheld devices differ from computers in viewing position and distance, screen size and luminance, and patterns of use. Accommodation is altered with handheld device use, with increased lag and decreased amplitude. Smartphone and tablet use results in reduced fusional convergence and possibly a receded near point of convergence. This is similar to what happens with computer use. Findings related to blink rate with smartphone and tablet use are contradictory, perhaps due to the influence of task difficulty, and there is limited evidence related to blink amplitude. Reduced blink rate and amplitude are consistently reported with computer use. Use of handheld digital devices, like computers, may adversely impact tear stability. There is insufficient evidence to support the impact of handheld devices on tear volume, although this is reduced with computer use. The available literature does not conclusively link eye and visual discomfort symptoms reported with handheld digital devices, with changes in binocular vision, blinking or ocular surface. However, there is a gap in our understanding of symptoms which occur with smartphone and tablet use in the context of how these devices are used. In addition, studies are required in high users such as teenagers, and in patients with dry eye or accommodative/binocular vision anomalies, all of whom may have a higher risk of symptoms. A better understanding of symptom aetiology can guide clinical advice to minimise adverse impacts on visual and ocular surface health and discomfort., (© 2019 Optometry Australia.)

Background: Computer vision syndrome is common and affects performance of visual tasks. Background illumination, light source, light compensation, position of the display, contrast and glare are environmental factors associated with computer vision syndrome. The aim of this study is to investigate the effects of reflected glare and visual field lighting on computer vision syndrome., Methods: In a reflected glare experiment, participants performed a two-hour visual task using a glossy, matte, or glare-free surface display in two visual environments (normal, glare). In a visual field lighting experiment, participants performed the visual task in dim lighting, uneven supplementary lighting, or uniform supplementary lighting. Visual function parameters, including critical fusion frequency, heterophoria, amplitude of accommodation and accommodative facility were evaluated by the investigators and a visual fatigue questionnaire was completed before and after the visual task. Visual performance was also recorded. In addition, the variation of pupil size under different lighting conditions was analysed., Results: Critical fusion frequency was the only visual function parameter which decreased significantly after the visual task. The questionnaire score was significantly higher in a glare environment and was lower when the task was performed using a glare-free display. Visual performance was significantly worse in the glossy display group. The increment in the questionnaire score was smaller in the uniform supplementary lighting group. Visual performance was significantly worse in the dim lighting or uneven supplementary lighting group, but not in the uniform supplementary lighting group. Variation in pupil size was significantly greater in the dim lighting condition than in the supplementary lighting condition., Conclusion: Critical fusion frequency is an effective indicator of computer vision syndrome. Glare-free displays could alleviate visual fatigue and preserve visual performance. Uniform supplementary lighting could decrease variation in pupil size and prevent eye strain., (© 2019 Optometry Australia.)

Significance: The present study addresses the accommodative response and its dependence on the type of optical correction used. The results are discussed relative to their possible implications for myopia progression and visual fatigue., Purpose: The accommodative response has been investigated owing to its possible relationship with the onset and progression of myopia and visual fatigue. This study explored the influence of wearing soft contact lenses in comparison with spectacles in terms of magnitude and variability of accommodation. In addition, we analyzed the intersession and intermethod repeatability., Methods: Dynamic accommodative response was recorded during 30-second epochs, at five different distances (50, 40, 33, 25, and 20 cm), in 21 individuals (mean refractive error ± SD, -0.79 ± 1.39 D) while wearing either soft contact lenses or spectacles on two different days. To assess repeatability, a second identical intervention was conducted., Results: Higher lags of accommodation were obtained with the use of soft contact lenses in comparison with the spectacle condition (P = .04, partial η [ηp] = 0.204), and similarly, a higher variability of accommodation at near distances was found during the soft contact lens measurement (P < .001, ηp = 0.647). There was a strong intersession repeatability at all the distances tested for both optical correction methods., Conclusions: The higher accommodative lag and fluctuations found while wearing soft contact lenses in comparison with spectacles may help to understand the mechanisms underlying myopia progression and asthenopia. These findings may be also considered when testing the accommodative response in research settings. Our test-retest design confirmed that there is a very good intersession repeatability for all the distances in both optical correction methods.

In augmented reality (AR) environments, information is often distributed between real world and virtual contexts, and often appears at different distances from the user. Therefore, to integrate the information, users must repeatedly switch context and refocus the eyes. To focus at different distances, the user's eyes must accommodate, which when done repeatedly can cause eyestrain and degrade task performance. An experiment was conducted that examined switching context and focal distance between a real and an AR environment, using a text-based visual search task and a monocular optical see-through AR display. Both context switching and focal distance switching resulted in significantly reduced performance. In addition, repeatedly performing the task caused visual fatigue to steadily increase. Performance was particularly poor for virtual text presented at optical infinity, and for target letters that participants tried to read before their eyes had completely accommodated to a new focal distance. The results show that context switching and focal distance switching are important AR user interface design issues.

This study was carried out to evaluate a method used to measure three-dimensional (3D) cognitive fatigue based on the pupillary response. This technique was designed to overcome measurement burdens by using non-contact methods. The pupillary response is related to cognitive function by a neural pathway and may be an indicator of 3D cognitive fatigue. Twenty-six undergraduate students (including 14 women) watched both 2D and 3D versions of a video for 70 min. The participants experienced visual fatigue after viewing the 3D content. Measures such as subjective rating, response time, event-related potential latency, heartbeat-evoked potential (HEP) alpha power, and task-evoked pupillary response (TEPR) latency were significantly different. Multitrait-multimethod matrix analysis indicated that HEP and TEPR latency measures had stronger reliability and higher correlations with 3D cognitive fatigue than other measures. TEPR latency may be useful for quantitatively determining 3D visual fatigue, as it can be easily used to evaluate 3D visual fatigue using a non-contact method without measuring burden.

Purpose: In this article, we develop a dynamic Bayesian network (DBN) model to measure 3D visual fatigue. As far as our information goes, this is the first adaptation of a DBN structure-based probabilistic framework for inferring the 3D viewer's state of visual fatigue., Methods: Our measurement focuses on the interdependencies between each factor and the phenomena of visual fatigue in stereoscopy. Specifically, the implementation of DBN with using multiple features (e.g. contextual, contactless and contact physiological features) and dynamic factor provides a systematic scheme to evaluate 3D visual fatigue., Results: In contrast to measurement results between the mean opinion score (MOS) and Bayesian network model (with static Bayesian network and DBN), the visual fatigue in stereoscopy at time slice t is influenced by a dynamic factor (time slice t-1). In the presence of dynamic factors (time slice t-1), our proposed measuring scheme based on DBN is more comprehensive., Conclusion: (i) We cover more features for inferring the visual fatigue, more reliably and accurately; (ii) at different time slices, the dynamic factor features are significant for inferring the visual fatigue state of stereoscopy., (© 2018 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.)

Purpose: The purpose of this study was to investigate the use of handheld digital devices and the prevalence of self-reported asthenopia among college students in China and their potential relationship., Methods: Five thousand students were randomly assessed using a self-reported asthenopia questionnaire. The students' demographic characteristics and habits regarding digital device use were recorded. Univariate analysis was performed to select potential risk factors, and multivariate logistic regression was used to estimate the odds ratios for the selected risk factors of interest., Results: Among the 4786 students who completed the survey, the prevalence of asthenopia was 53.3%. Multivariate analysis revealed significant relationships between asthenopia and each of the following: level of digital reliance (OR 1.350, 95%CI: 1.230-1.481), workload, time spent on computer per day, sex and time spent on handheld digital devices in bed and at desk. Aerobic exercise duration (OR 0.912, 95%CI: 0.839-0.990) was found to be strong predictor of less asthenopia complaints., Conclusion: Asthenopia appears to be common among college students in China. Preventative measures against asthenopia include limiting the amount of time spent using digital devices in bed (<0.5 h), adopting a posture of lying on one's back while doing so and engaging in aerobic exercise for more than one hour per day. Furthermore, studies on this topic are needed., (© 2018 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.)

Eye fatigue is a common health problem across all age groups. Herein, we explored the correlation between eye fatigue and thickness of the retinal nerve fiber layer (NFL). Included in the NFL are intrinsically photosensitive retinal ganglion cells (ipRGCs), which are associated with trigeminal pain. This retrospective cross-sectional study included outpatients with best-corrected visual acuity above 20/30 in both eyes and without dry eye, glaucoma, or retinal disease. A total of 1981 patients were initially enrolled and 377 patients were declared as eligible for the study analysis. We tested subjects for the presence of major ocular symptoms and measured thickness of ganglion cell complex (GCC) using optical coherence tomography. A total of 377 outpatients (46.4% men, mean age of 57.1 years) were enrolled for analysis, based on the interview-reported prevalence of six eye symptom, as follows: 31.5% for eye fatigue, 19.2% for blurring, 18.6% for dryness, 15.7% for photophobia, 13.5% for irritation, and 4.6% for pain. The macular GCC was significantly thicker in subjects with eye fatigue compared to the group not reporting eye fatigue (103.8  μ m versus 100.3  μ m, P = 0.014). Regression analysis identified eye fatigue ( P = 0.026, β =0.122, adjusted for age and sex) and dryness ( P =0.024, β =0.130) as significantly correlated with the macular GCC thickness, while the full macular thickness showed no significant correlation. In conclusions, eye fatigue and dryness were positively associated with thickness of the macular GCC. Nonvisual symptoms might therefore play a role in the development of eye fatigue.

Vergence prism adaptability was evaluated in subjects with high symptomatic and asymptomatic heterophoria and compared to individuals with a heterophoria within normal range (the control group). A computer haploscope was used to measure phoria values and changes in the eye position after introducing 6 prism diopters base out in front of the right eye. Phoria values were measured with a nonius paradigm every minute for a period of 10 minutes during adaptation. The results showed that subjects with symptomatic heterophoria are characterized by a lower rate of prism adaptation and adapted to a smaller extent with respect to the control group. The group with high but asymptomatic heterophoria showed prolonged adaptation time but after several minutes of binocular viewing the subjects were able to adapt to the prism to a level similar to the control group. These findings suggest that an impairment in the slow vergence control system may be responsible for the inability to fully reduce vergence effort, which results in poor vergence ranges and asthenopic symptoms during prolonged viewing., Competing Interests: The authors have declared that no competing interests exist.

Objectives: To compare the effect of toric versus spherical soft contact lenses on objective measures of visual performance using visual acuity and electromyography of the orbicularis oculi muscle., Methods: Current soft contact lens wearers with -0.75 to -1.75 D astigmatism in each eye were binocularly fitted with toric (1-Day ACUVUE MOIST for astigmatism) and spherical (1-Day ACUVUE MOIST) contact lenses in random order. After each fitting and at 1-week follow-up, high- and low-contrast visual acuities were measured. Electromyography was used to objectively evaluate eyestrain. Linear mixed models were used to assess differences between toric and spherical contact lenses., Results: The mean age (±SD) of the 60 participants was 27.5±5.0 years, spherical refractive error was -3.68±2.01 D, and cylinder was -1.28±0.36 D. High- and low-contrast visual acuities with toric lenses were better than with spherical lenses at both fitting (toric high-contrast: -0.065±0.078 and low-contrast: 0.133±0.103 vs. spherical high-contrast: 0.001±0.104 and low-contrast: 0.224±0.107) and follow-up (toric high-contrast: -0.083±0.087 and low-contrast: 0.108±0.107 vs. spherical high-contrast: -0.015±0.095 and low-contrast: 0.211±0.104) (all P<0.0001). Electromyography-measured eyestrain was less with toric versus spherical contact lenses at fitting (least-square ratio of toric over spherical=0.72; P=0.0019) but not at follow-up (ratio=0.86; P=0.11)., Conclusion: These results suggest that toric contact lenses provided improved objective measures of vision in a low-to-moderate astigmatic population.

Background: Visual display terminals (VDTs) emitting blue light can cause ocular disorders including eye fatigue. Some dietary constituents have been reported to be effective in improving ocular disorders while few clinical studies have been performed. We evaluated the effects of heat-killed Lactobacillus paracasei KW 3110 on improving ocular disorders and symptoms of eye fatigue among healthy human subjects with VDT loads., Methods: In vitro, the effect of L. paracasei KW3110 on blue light-induced human retinal pigment epithelial (ARPE-19) cell damage. For clinical studies, 62 healthy Japanese volunteers of 35 to 45 years of age who had experienced eye fatigue were randomized into two groups and given a placebo or L. paracasei KW3110-containing supplements for eight weeks. The primary endpoint was changes in VDT load-induced eye fatigue as determined by critical flicker frequency four and eight weeks after the start of supplementation., Results: In vitro, blue light-induced human retinal cell death was suppressed with the culture supernatants of cells treated with L. paracasei KW3110. In clinical study, the VDT load-induced reduction of critical flicker frequency tended to be milder in the L. paracasei KW3110 group when compared with the placebo group during the fourth week. Subgroup analysis classified by the degree of eye fatigue showed that the VDT load-induced reduction of critical flicker frequency was significantly better in the high-level eye fatigue subjects from the L. paracasei KW3110 group when compared with the placebo group during the fourth week ( p = 0.020)., Conclusions: L. paracasei KW3110 suppressed blue light-induced retinal pigment epithelial cell death. In the clinical study, ingestion of L. paracasei KW3110 had a potential to improve eye fatigue induced by VDT loads especially high levels of eye fatigue. However, further studies should be required to show more dependable clinical efficacy of L. paracasei KW3110., Competing Interests: The funder designed this study and supplied the test tablets and placebo. The funder had no role in data collection nor data analysis. This manuscript was prepared by the members of the funder. The funder decided to publish the results.

Purpose: To study the accommodative dynamics for predictable and unpredictable stimuli using manual and automated accommodative facility tests Materials and Methods: Seventeen young healthy subjects were tested monocularly in two consecutive sessions, using five different conditions. Two conditions replicated the conventional monocular accommodative facility tests for far and near distances, performed with manually held flippers. The other three conditions were automated and conducted using an electro-optical system and open-field autorefractor. Two of the three automated conditions replicated the predictable manual accommodative facility tests. The last automated condition was a hybrid approach using a novel method whereby far and near-accommodative-facility tests were randomly integrated into a single test of four unpredictable accommodative demands., Results: The within-subject standard deviations for far- and near-distance-accommodative reversals were (±1,±1) cycles per minute (cpm) for the manual flipper accommodative facility conditions and (±3, ±4) cpm for the automated conditions. The 95% limits of agreement between the manual and the automated conditions for far and near distances were poor: (-18, 12) and (-15, 3). During the hybrid unpredictable condition, the response time and accommodative response parameters were significantly (p < 0.05) larger for accommodation than disaccommodation responses for high accommodative demands only. The response times during the transitions 0.17/2.17 D and 0.50/4.50 D appeared to be indistinguishable between the hybrid unpredictable and the conventional predictable automated tests., Conclusions: The automated accommodative facility test does not agree with the manual flipper test results. Operator delays in flipping the lens may account for these differences. This novel test, using unpredictable stimuli, provides a more comprehensive examination of accommodative dynamics than conventional manual accommodative facility tests. Unexpectedly, the unpredictability of the stimulus did not to affect accommodation dynamics. Further studies are needed to evaluate the sensitivity of this novel hybrid technique on individuals with accommodative anomalies.

Significance: Growing popularity of handheld digital devices imposes significant challenges to our visual system and clinical management. This study aimed to determine the effects of lens design on parameters that may influence the refractive management of pre-presbyopic adult computer users., Purpose: To determine the effects of wearing conventional single-vision lenses (SVL) versus progressive addition lenses (PAL) on the working distance and refractive status., Methods: Adult computer users, recruited from two age cohorts (18 to 25 years, n = 19; 30 to 40 years, n = 45), were prescribed SVLs and PALs designed for use with handheld digital devices. For each lens type, the working distance and refractive shift (post-task - pre-task) were measured immediately after lens delivery (T0) and after 1 month of lens wear (T1). Working distances were recorded with an automatic ultrasound device while the participants were playing a video game. Refractive status through the subjects' glasses was measured before (pre-task) and after playing the game (post-task). Questionnaires assessing the frequencies of 10 digital work-related visual symptoms were conducted for both lens types at T1., Results: Switching from SVL to PAL increased the working distance in both cohorts (mean ± SEM = 1.88 ± 0.60 cm; P = .002) and induced a small but significant positive refractive shift (+0.08 ± 0.04 D, P = .021) in the older cohort at T1. In the younger cohort, the changes in working distance due to the switching lens design were correlated with myopic error (r = +0.66, P = .002). In the older cohort, the changes in refractive shift due to switching lens design were correlated with amplitude of accommodation at both time points (r for T0 and T1 = -0.32 and -0.30, respectively; both P < .05). Progressive addition lens was rated as causing less "increased sensitivity to light" compared with SVL., Conclusions: Switching from SVL to PAL increased the working distance and induced a positive refractive shift in the majority of pre-presbyopic adults.

Background and Objective: To examine the human visual performance (wavefront aberration) and subjective questionnaire (SQ) of visual fatigue when viewing 2-D and 3-D movies., Methods: Thirty healthy adults observed 2-D and 3-D movies on the same television from a 3m distances during 2D, 3D-A (with better 3D glasses), and 3D-B (with poorer 3D glasses) viewing conditions. Visual quality index, including modulation transfer function index (MTFI), higher order aberration root mean square (RMS), vertical coma (VC), horizontal coma (HC) and spherical aberration (SA), were assessed before and after each viewing condition. One-way repeated measures ANOVA was performed to assess the changes of each test variable before and after movie viewing., Results: Participants watching movies with 3D-B conditions experienced higher change of MTFI, RMS, VC and HC but smaller SQ, compared with 2D and 3D-A (P< 0.05). Additionally, higher MTFI but smaller SQ was found for 3D-A compared with 2D viewing condition (P< 0.05)., Conclusions: While prolonged viewing 2-D and 3-D movies would lead to poorer visual performance, 3-D glasses with better quality can play the major role in reducing visual ability for users. The change of human eye wavefront aberration might be useful for the evaluation of visual fatigue in the future.

Purpose: To examine a possible relationship between exposure to video games/electronic screens and visual issues in children between 3 and 10 years of age., Methods: An observational, cross-sectional study of a population of children using video games was employed. All patients between 3 and 10 years of age were recruited at an outpatient unit accredited by the Italian Regional Health Service. Three hundred twenty children (159 boys and 161 girls; mean age = 6.9 ± 2 years) were observed. Ophthalmological examination included assessment of stereoscopic vision on Lang-Stereotests I and II (LANG-STEREOTEST AG, Küsnacht, Switzerland) and identification of the dominant eye using the Dolman method. Furthermore, a questionnaire was used to record asthenopic symptoms and daily exposure to video games and electronic screens. Two groups of children were examined according to the average amount of time spent playing video games daily: children who played video games for less than 30 minutes per day and not every day (control group) and children who played video games for 30 minutes or more every day (video game group). Both groups were then divided into two subgroups: children using other types of electronic screens (eg, televisions, computers, tablets, and smartphones) for less than 3 hours daily (low electronic use subgroup) and children using other types of electronic screens for 3 hours or more per day (high electronic use subgroup)., Results: Asthenopia (especially headache, eyelid tic, transient diplopia, and dizziness), absence of fine stereopsis, and refractive errors were statistically more frequent (mainly in the dominant eye) in children in the video game group., Conclusions: These symptoms were frequent and peculiar in the video game group and might be part of a video game vision syndrome that has not been defined yet. It is important to recognize these signs as possible functional disorders to avoid erroneous diagnostic and therapeutic interventions. [J Pediatr Ophthalmol Strabismus. 2017;54(6):346-355.]., (Copyright 2017, SLACK Incorporated.)

Purpose: In the present study, the visual discomfort induced by smart mobile devices was assessed in normal and healthy adults., Methods: Fifty-nine volunteers (age, 38.16 ± 10.23 years; male : female = 19 : 40) were exposed to tablet computer screen stimuli (iPad Air, Apple Inc.) for 1 hour. Participants watched a movie or played a computer game on the tablet computer. Visual fatigue and discomfort were assessed using an asthenopia questionnaire, tear film break-up time, and total ocular wavefront aberration before and after viewing smart mobile devices., Results: Based on the questionnaire, viewing smart mobile devices for 1 hour significantly increased mean total asthenopia score from 19.59 ± 8.58 to 22.68 ± 9.39 (p < 0.001). Specifically, the scores for five items (tired eyes, sore/aching eyes, irritated eyes, watery eyes, and hot/burning eye) were significantly increased by viewing smart mobile devices. Tear film break-up time significantly decreased from 5.09 ± 1.52 seconds to 4.63 ± 1.34 seconds (p = 0.003). However, total ocular wavefront aberration was unchanged., Conclusions: Visual fatigue and discomfort were significantly induced by viewing smart mobile devices, even though the devices were equipped with state-of-the-art display technology., Competing Interests: No potential conflict of interest relevant to this article was reported., (© 2017 The Korean Ophthalmological Society)

Purpose: Visual stress (VS) is characterised by symptoms of visual perceptual distortions and eyestrain when viewing text, symptoms that are alleviated by individually prescribed coloured filters. A recent review supports the existence of VS and its treatment, but noted that controversy remains, in part due to inconsistencies in the diagnosis of the condition. The present paper reviews the diagnostic criteria for VS in the literature and reports a Delphi analysis of the criteria currently used in clinical practice., Methods: Twenty-six eyecare practitioners were invited to participate in a Delphi study. They were selected because they were frequent prescribers of precision tinted lenses. In the first round they were sent a list of the indicators for which there is literature to suggest a relevance in the diagnosis of VS. The practitioners were invited to rank the indicators and add any additional criteria they use in diagnosis. In the second round a revised list was circulated, including items added from the responses in the first round., Results: The respondents included optometrists, orthoptists and opticians. In the first round the response rate was 85%. Ninety-one percent of those who participated in the first round also responded in the second round. Strong indicators in the second round included the symptom of words moving when reading, voluntary use of an overlay for a prolonged period, improved performance of ≥15% with an overlay on the Wilkins Rate of Reading test, and an abnormally high score on the Pattern Glare Test., Conclusions: The strongest diagnostic criteria are combined in a diagnostic tool. This is proposed as a guide for clinical practice and further research., (Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Purpose: When observers focus their stereoscopic visual system for a long time (e.g., watching a 3D movie) they may experience visual discomfort or asthenopia. We tested two types of models for predicting visual fatigue in a task in which subjects were instructed to discriminate between 3D characters. One model was based on viewing distance (focal distance, vergence distance) and another in visual direction (oculomotor imbalance)., Method: A 3D test was designed to assess binocular visual fatigue while looking at 3D stimuli located in different visual directions and viewed from two distances from the screen. The observers were tested under three conditions: (a) normal vision; (b) wearing a lens (-2 diop.); (c) wearing a base-out prism (2▿) over each eye. Sensitivity and specificity were calculated (as Signal Detection Theory parameters: SDT)., Results: An ANOVA and SDT analyses revealed that impaired visual performance were directly related to short distance and larger deviation in visual direction, particularly when the stimuli were located nearer and at more than 24° to the centre of the screen in dextroversion and beyond., Conclusion: This results support a mixed model, combining a model based on the visual angle (related to viewing distance) and another based on the oculomotor imbalance (related to visual direction). This mixed model could help to predict the distribution of seats in the cinema room ranging from those that produce greater visual comfort to those that produce more visual discomfort. Also could be a first step to pre-diagnosis of binocular vision disorders., (Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Objective: The effects of performing a 90-minute computer task with a laptop versus a dual monitor desktop workstation were investigated in healthy young male and female adults., Background: Work-related musculoskeletal disorders are common among computer (especially female) users. Laptops have surpassed desktop computer sales, and working with multiple monitors has also become popular. However, few studies have provided objective evidence on how they affect the musculoskeletal system in both genders., Methods: Twenty-seven healthy participants (mean age = 24.6 years; 13 males) completed a 90-minute computer task while using a laptop or dual monitor (DualMon) desktop. Electromyography (EMG) from eight upper body muscles and visual strain were measured throughout the task. Neck proprioception was tested before and after the computer task using a head-repositioning test. EMG amplitude (root mean square [RMS]), variability (coefficients of variation [CV]), and normalized mutual information (NMI) were computed., Results: Visual strain ( p < .01) and right upper trapezius RMS ( p = .03) increased significantly over time regardless of workstation. Right cervical erector spinae RMS and cervical NMI were smaller, while degrees of overshoot (mean = 4.15°) and end position error (mean = 1.26°) were larger in DualMon regardless of time. Effects on muscle activity were more pronounced in males, whereas effects on proprioception were more pronounced in females., Conclusion: Results suggest that compared to laptop, DualMon work is effective in reducing cervical muscle activity, dissociating cervical connectivity, and maintaining more typical neck repositioning patterns, suggesting some health-protective effects., Application: This evidence could be considered when deciding on computer workstation designs.

Background: With the increasing prevalence of electronic readers (e-readers) for vocational and professional uses, it is important to discover if there are visual consequences in the use of these products. There are no studies in the literature quantifying the incidence or severity of eyestrain, nor are there clinical characteristics that may predispose to these symptoms with e-reader use., Purpose: The primary objective of this pilot study was to assess the degree of eyestrain associated with e-reader use compared to traditional paper format. The secondary outcomes of this study were to assess the rate of eyestrain associated with e-reader use and identify any clinical characteristics that may be associated with the development of eyestrain., Methods: Forty-four students were randomly assigned to study (e-reader iPAD) and control (print) groups. Participant posture, luminosity of the room, and reading distance from reading device were measured during a 1-h session for both groups. At the end of the session, questionnaires were administered to determine symptoms., Results: Significantly higher rates of eyestrain (p = 0.008) and irritation (p = 0.011) were found among the iPAD study group as compared to the print 'control' group. The study group was also 4.9 times more likely to report severe eyestrain (95 % CI [1.4, 16.9]). No clinical characteristics predisposing to eyestrain could be identified., Conclusions: These findings conclude that reading on e-readers may induce increased levels of irritation and eyestrain. Predisposing factors, etiology, and potential remedial interventions remain to be determined.

This study examined the effects of display curvature (400, 600, 1200 mm, and flat), display zone (5 zones), and task duration (15 and 30 min) on legibility and visual fatigue. Each participant completed two 15-min visual search task sets at each curvature setting. The 600-mm and 1200-mm settings yielded better results than the flat setting in terms of legibility and perceived visual fatigue. Relative to the corresponding centre zone, the outermost zones of the 1200-mm and flat settings showed a decrease of 8%-37% in legibility, whereas those of the flat setting showed an increase of 26%-45% in perceived visual fatigue. Across curvatures, legibility decreased by 2%-8%, whereas perceived visual fatigue increased by 22% during the second task set. The two task sets induced an increase of 102% in the eye complaint score and a decrease of 0.3 Hz in the critical fusion frequency, both of which indicated an increase in visual fatigue. In summary, a curvature of around 600 mm, central display zones, and frequent breaks are recommended to improve legibility and reduce visual fatigue., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Functional near-infrared spectroscopy (fNIRS) was adopted to investigate the cortical neural correlates of visual fatigue during binocular depth perception for different disparities (from 0.1° to 1.5°). By using a slow event-related paradigm, the oxyhaemoglobin (HbO) responses to fused binocular stimuli presented by the random-dot stereogram (RDS) were recorded over the whole visual dorsal area. To extract from an HbO curve the characteristics that are correlated with subjective experiences of stereopsis and visual fatigue, we proposed a novel method to fit the time-course HbO curve with various response functions which could reflect various processes of binocular depth perception. Our results indicate that the parietal-occipital cortices are spatially correlated with binocular depth perception and that the process of depth perception includes two steps, associated with generating and sustaining stereovision. Visual fatigue is caused mainly by generating stereovision, while the amplitude of the haemodynamic response corresponding to sustaining stereovision is correlated with stereopsis. Combining statistical parameter analysis and the fitted time-course analysis, fNIRS could be a promising method to study visual fatigue and possibly other multi-process neural bases.

Commonly conflated with sleepiness, fatigue is a distinct multidimensional condition with physical and mental effects. Fatigue in health care providers and any secondary effects on patient care are an important societal concern. As medical image interpretation is highly dependent on visual input, visual fatigue is of particular interest to radiologists. Humans analyze their surroundings with rapid eye movements called saccades, and fatigue decreases saccadic velocity. Oculomotor parameters may, therefore, be an objective and reproducible metric of fatigue and eye movement analysis can provide valuable insight into the etiology of fatigue-related error., (Copyright © 2016 American College of Radiology. Published by Elsevier Inc. All rights reserved.)

To explore the bridge role of Jingming (BL 1) for video display terminal (VDT) asthenopia and brainfag. Ancient literature and modern scientific research on the acupoint have been analyzed and summarized so as to explore pressing the acupoint the instinct feedback of brain after asthenopia. It is demonstrated that Jingming (BL 1) is a key channel between eyes, brain and the outside world, and it is one of major feedback points of brain after asthenopia. In this paper we try to establish a new research thinking and ascertain it, namely Jingming (BL 1) reflecting the relationship between asthenopia and brainfag. We hope that it can provide some references for further research on cognizing brain through eye.

Purpose: To investigate the efficacy of evaluating 3D asthenopia and 3D perception difficulty for screening of binocular vision abnormalities in children., Methods: Patients aged 6-12 years with abnormal binocularity, including strabismus, amblyopia, and anisometropia, were included. Age-matched normal subjects without any ophthalmologic abnormality other than a refractive error were also recruited. The best-corrected visual acuity, refractive error, angle of strabismus, and stereopsis were measured. Presenting visual acuity (PVA) was measured as the uncorrected visual acuity for subjects without glasses and spectacle-corrected visual acuity for those with glasses. After watching 3D TV for 30 min, a survey was administered to evaluate the 3D perception and 3D asthenopia. Receiver operation characteristic (ROC) curve analysis was conducted to evaluate the efficacy of the survey for detecting abnormal binocularity and poor PVA., Results: One hundred subjects were enrolled in this study. Among them, 59 had abnormal binocularity (strabismus, anisometropia, or amblyopia), and 41 were normal control. Among the entire subjects, the number of subjects with a PVA of 20/40 or worse in one or both eyes was 24 (7 from the normal control and 17 with abnormal binocularity). ROC curve analysis revealed that the survey did not effectively detect strabismus, anisometropia, or amblyopia. However, for detection of PVA 20/40 or worse in the subjects with abnormal binocularity, the total score of the survey yielded an area of 0.714 under the ROC curve (p = 0.010). The sensitivity was 88.2% and specificity was 61.9% with a cutoff at 0.50., Conclusion: The degree of 3D asthenopia and 3D perception while watching 3D TV were not effective for screening of abnormal binocularity. However, evaluation of the severity of 3D asthenopia and the quality of 3D perception can help screen of decrease in PVA that requires correction.

Purpose: Unfavorable visual conditions during computer work may affect development of both eyestrain and musculoskeletal pain in the neck and shoulder area. The aim of the study was to investigate how direct glare affects symptom development, muscle activity, and muscle blood flow in m. orbicularis oculi and m. trapezius during reading on a computer screen., Methods: Fifteen healthy young adults with normal binocular vision read text on a computer screen at an optimized computer workplace, 30 minutes with glare exposure and 30 minutes with appropriate lighting. Postural angles were continuously registered. Development of eye symptoms and musculoskeletal pain in the neck and shoulder area were recorded using VAS scales. Muscle activity and muscle blood flow were measured continuously using electromyography and photoplethysmography, respectively., Results: Glare exposure resulted in significantly more pronounced eye pain, increased orbicularis muscle activity, and increased trapezius blood flow compared to reading with appropriate lighting. There were no significant differences in posture between the two light conditions. There were also significant associations between orbicularis oculi activity and both trapezius blood flow and neck pain during both conditions., Conclusions: Results from the current study show that direct glare conditions cause increased eyestrain and orbicularis oculi contraction during reading on a computer screen. This study also indicates that exposure to direct glare affects the trapezius muscle, possibly by an interaction between the visual system, sympathetic nervous system, and head-stabilizing muscles. In addition, there were associations between the use of orbicularis oculi, trapezius blood flow, and development of neck pain independent of the lighting.

It has been shown that the same canonical cortical circuit model with mutual inhibition and a fatigue process can explain perceptual rivalry and other neurophysiological responses to a range of static stimuli. However, it has been proposed that this model cannot explain responses to dynamic inputs such as found in intermittent rivalry and rivalry memory, where maintenance of a percept when the stimulus is absent is required. This challenges the universality of the basic canonical cortical circuit. Here, we show that by including an overlooked realistic small nonspecific background neural activity, the same basic model can reproduce intermittent rivalry and rivalry memory without compromising static rivalry and other cortical phenomena. The background activity induces a mutual-inhibition mechanism for short-term memory, which is robust to noise and where fine-tuning of recurrent excitation or inclusion of sub-threshold currents or synaptic facilitation is unnecessary. We prove existence conditions for the mechanism and show that it can explain experimental results from the quartet apparent motion illusion, which is a prototypical intermittent rivalry stimulus.

Background: Computer vision syndrome (CVS) is a group of visual symptoms experienced in relation to the use of computers. Nearly 60 million people suffer from CVS globally, resulting in reduced productivity at work and reduced quality of life of the computer worker. The present study aims to describe the prevalence of CVS and its associated factors among a nationally-representative sample of Sri Lankan computer workers., Methods: Two thousand five hundred computer office workers were invited for the study from all nine provinces of Sri Lanka between May and December 2009. A self-administered questionnaire was used to collect socio-demographic data, symptoms of CVS and its associated factors. A binary logistic regression analysis was performed in all patients with 'presence of CVS' as the dichotomous dependent variable and age, gender, duration of occupation, daily computer usage, pre-existing eye disease, not using a visual display terminal (VDT) filter, adjusting brightness of screen, use of contact lenses, angle of gaze and ergonomic practices knowledge as the continuous/dichotomous independent variables. A similar binary logistic regression analysis was performed in all patients with 'severity of CVS' as the dichotomous dependent variable and other continuous/dichotomous independent variables., Results: Sample size was 2210 (response rate-88.4%). Mean age was 30.8 ± 8.1 years and 50.8% of the sample were males. The 1-year prevalence of CVS in the study population was 67.4%. Female gender (OR: 1.28), duration of occupation (OR: 1.07), daily computer usage (1.10), pre-existing eye disease (OR: 4.49), not using a VDT filter (OR: 1.02), use of contact lenses (OR: 3.21) and ergonomics practices knowledge (OR: 1.24) all were associated with significantly presence of CVS. The duration of occupation (OR: 1.04) and presence of pre-existing eye disease (OR: 1.54) were significantly associated with the presence of 'severe CVS'., Conclusions: Sri Lankan computer workers had a high prevalence of CVS. Female gender, longer duration of occupation, higher daily computer usage, pre-existing eye disease, not using a VDT filter, use of contact lenses and higher ergonomics practices knowledge all were associated with significantly with the presence of CVS. The factors associated with the severity of CVS were the duration of occupation and presence of pre-existing eye disease.

Purpose: To examine clinical preoperative and postoperative symptoms and changes in exotropia according to constancy and age., Methods: A survey was conducted of 50 patients on the day before and 1 month after exotropia surgery. Survey results were analyzed by type of exotropia at presentation and age. Changes in subjective symptoms from preoperatively to postoperatively were examined for stereopsis (5 items), asthenopia (5 items), and appearance (5 items). Each item was rated on a 5-point scale ranging from 0 to 4., Results: The mean age of the 50 patients was 10.6 ± 7.75 years, and there were 21 (41.2%) males and 29 (56.9%) females. Thirty-two patients with intermittent exotropia had no significant improvement in the stereopsis or asthenopia symptoms. However, they showed significant (P < .05) improvement in the appearance symptoms of squint and out of focus. Eighteen patients with constant exotropia showed significant improvements in the symptoms of tripping over objects or running into a wall in stereopsis and of squint and out of focus in appearance (P < .05). Postoperatively, all patients had significant improvement in appearance-related symptoms regardless of age (P < .05)., Conclusions: Patients with constant exotropia had improved symptoms in stereopsis, asthenopia, and appearance after surgery. Appearance was improved regardless of the type of exotropia or age., (Copyright 2016, SLACK Incorporated.)

The objective of this study was to determine vulnerability to pattern-related visual stress in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). A total of 20 ME/CFS patients and 20 matched (age, gender) controls were recruited to the study. Pattern-related visual stress was determined using the Pattern Glare Test. Participants viewed three patterns, the spatial frequencies (SF) of which were 0.3 (low-SF), 2.3 (mid-SF), and 9.4 (high-SF) cycles per degree (c/deg). They reported the number of distortions they experienced when viewing each pattern. ME/CFS patients exhibited significantly higher pattern glare scores than controls for the mid-SF pattern. Mid-high SF differences were also significantly higher in patients than controls. These findings provide evidence of altered visual perception in ME/CFS. Pattern-related visual stress may represent an identifiable clinical feature of ME/CFS that will prove useful in its diagnosis. However, further research is required to establish if these symptoms reflect ME/CFS-related changes in the functioning of sensory neural pathways., (© The Author(s) 2015.)

High comorbidity and an overlap in symptomology have been demonstrated between dyslexia and visual stress. Several researchers have hypothesized an underlying or causal influence that may account for this relationship. The magnocellular theory of dyslexia proposes that a deficit in visuo-temporal processing can explain symptomology for both disorders. If the magnocellular theory holds true, individuals who experience symptomology for these disorders should show impairment on a visuo-temporal task, such as driving. Eighteen male participants formed the sample for this study. Self-report measures assessed dyslexia and visual stress symptomology as well as participant IQ. Participants completed a drive simulation in which errors in response to road signs were measured. Bivariate correlations revealed significant associations between scores on measures of dyslexia and visual stress. Results also demonstrated that self-reported symptomology predicts magnocellular impairment as measured by performance on a driving task. Results from this study suggest that a magnocellular deficit offers a likely explanation for individuals who report high symptomology across both conditions. While conclusions about the impact of these disorders on driving performance should not be derived from this research alone, this study provides a platform for the development of future research, utilizing a clinical population and on-road driving assessment techniques., (Copyright © 2015 John Wiley & Sons, Ltd.)

Purpose: To evaluate the efficacy of a home-based computer orthoptic program for symptomatic convergence insufficiency (CI) in children., Methods: The medical records of participants aged 5 to <18 years who were diagnosed with symptomatic CI and were treated with the Computerized Vergence System (CVS) program were retrospectively reviewed. All participants were prescribed 9 or 15 minutes of daily convergence exercises with the CVS program, 5 days per week, for the initial 6 weeks. Near point of convergence (NPC) and near convergence amplitude (NCA) were measured at baseline, 6 week, and final examinations. The presence or absence of diplopia and asthenopia with reading were recorded at baseline and final examinations., Results: A total of 186 participants were included. At diagnosis, 72 participants (39%) reported diplopia and 182 (98%), reported asthenopia. At final examination, 172 participants (92%) were asymptomatic. Twelve participants (6%) subsequently received other treatment modalities. Mean NPC at baseline (5.9 cm) improved after 6 weeks of CVS therapy (3.3 cm) and at final examination (2.9 cm; P < 0.0005). Mean NCA at baseline (20.3(Δ)) improved after 6 weeks of CVS therapy (37.0(Δ)) and at the final examination (38.0(Δ); P < 0.0005)., Conclusions: In this study, home-based CVS therapy reduced symptoms related to CI and improved the NPC and NCA of most children aged 5 to <18 years with symptomatic CI., (Copyright © 2015 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.)