Assessment of visual fatigue in SSVEP-based brain-computer interface: a comprehensive study.

Fatigue deteriorates the performance of a brain-computer interface (BCI) system; thus, reliable detection of fatigue is the first step to counter this problem. The fatigue evaluated by means of electroencephalographic (EEG) signals has been studied in many research projects, but widely different results have been reported. Moreover, there is scant research when considering the fatigue on steady-state visually evoked potential (SSVEP)-based BCI. Therefore, nowadays, fatigue detection is not a completely solved topic. In the current work, the issues found in the literature that led to the differences in the results are identified and saved by performing a new experiment on an SSVEP-based BCI system. The experiment was long enough to produce fatigue in the users, and different SSVEP stimulation ranges were used. Additionally, the EEG features commonly reported in the literature (EEG rhythms powers, SNR, etc.) were calculated as well as newly proposed features (spectral features and Lempel-Ziv complexity). The analysis was carried out on O1, Oz and O2 channels. This work found a tendency of displacement from high-frequency rhythms to low-frequency ones, and thus, better EEG features should present a similar behaviour. Then, the 'relative power' of EEG rhythms, the rates (θ + α)/ß, α/ß and θ/ß, some spectral features (central and mean frequencies, asymmetry and kurtosis coefficients, etc.) and Lempel-Ziv complexity are proposed as reliable EEG features for fatigue detection. Hence, this set of features may be used to construct a more trustworthy fatigue index.

A multicenter survey of effects and challenges of an 8K ultra-high-definition endoscopy system compared to existing endoscopy systems for endoscopic surgery.

INTRODUCTION: 8K ultra-high-definition (UHD) images enabling clearer recognition of anatomical structures could contribute to further development of surgical techniques and advanced applications in endoscopic surgery fields. This study aimed to clarify effects and challenges of endoscopic surgery with 8K UHD endoscopy compared to existing endoscopy systems. METHODS: In this multicenter, cross-sectional, questionnaire survey, data were collected from surgical participants who newly used and observed 8K UHD endoscopy in patients undergoing surgery from February 2020 to February 2021. Survey items included sense of presence, reality, depth perception, visibility of tissue, eyestrain, and degree of satisfaction for operators and observers, and weight, operability, focus adjustment, physical fatigue, eyestrain, and satisfaction for camera assistants. Participants rated each 8K UHD endoscopic surgery on a one-to-five scale (definitively inferior, relatively inferior, equivalent, relatively superior, definitively superior) compared to the existing endoscopy system of each facility. RESULTS: Overall, questionnaire responses from 139 participants assessing 8K UHD endoscopic surgery were collected from surgeries performed in 46 patients. Respective ratings of operators and observers included sense of presence: "superior or relatively superior", 97.8% and 91.5%; reality: "superior or relatively superior", 76.1% and 72.3%; and visibility of tissue: "superior or relatively superior", 93.5% and 87.2%. Weight was rated as "inferior or relatively inferior" by 73.9% of camera assistants and focus adjustment as "inferior" by 60.9% of them. CONCLUSIONS: 8K UHD endoscopic surgery enabled identification of surgical anatomies more clearly, provided a sense of presence and reality, and might improve educational effect. Technological development is expected to reduce the burden of camera assistants.

[Digital eye strain. Symptoms, prevalence, pathophysiology, and management]. / Perturbations oculaires secondaires à l'utilisation de supports numériques. Symptômes, prévalence, physiopathologie et prise en charge.

The digital revolution, which has been underway since the 1980's, is disrupting our daily routines with an exponential increase in the use of screens, which has not been without consequence to our visual system. Digital eye strain (DES), or computer vision syndrome (CVS), includes all the visual symptoms secondary to the use of digital devices. DES is present in at least 50% of regular users of digital media and is defined by blurred vision, difficulty focusing, ocular irritation or burning, dry eye, visual fatigue, headaches and increased sensitivity to light. Exposure time, age, female gender, and work environment are the main factors increasing its prevalence. Its pathophysiology, still poorly understood, is felt to be multifactorial and includes disturbances in the accommodative-convergence balance and changes in the ocular surface. Regarding accommodation and convergence, the studies are mostly old and their results heterogeneous. Conversely, many studies have shown an increase in the prevalence of dry eye in screen users. Although the retinal toxicity of blue light has been proven in in vitro models, the low level of evidence in the available studies does not allow it to be clearly correlated with the symptoms of DES. The objective of this review is to condense the knowledge available in the literature on the symptoms, prevalence, pathophysiology and management of DES.

Prevalence and risk factor assessment of digital eye strain among children using online e-learning during the COVID-19 pandemic: Digital eye strain among kids (DESK study-1).

Purpose: The aim of this study was to determine prevalence, symptoms frequency and associated risk factors of digital eye strain (DES) among children attending online classes during COVID-19 pandemic. Methods: The online electronic survey form was prepared on the Google app. Children/parents were asked to indicate the total duration of digital device use before and during COVID era. The symptoms of DES, its severity and frequency were recorded & measured with the Computer Vision Syndrome Questionnaire. Results: Two hundred and sixty one parents responded to the questionnaire, of these 217 were complete. Mean age of children was 13 ± 2.45 years. Mean duration of digital device used during COVID era was 3.9 ± 1.9 h which is more than pre COVID era (1.9 ± 1.1 h, P = <0.0001). 36.9% (n = 80) were using digital devices >5 h in COVID era as compared to 1.8% (n = 4) before COVID era. The most common digital device used were smartphones (n = 134, 61.7%). One hundred and eight children (49.8%) were attending online classes for >2 h per day. Prevalence of DES in our cohort is 50.23% (109/217). Of these 26.3% were mild, 12.9% moderate and 11.1% of severe grade. Most common symptoms were itching and headache (n = 117, 53.9%). Multivariate analysis revealed age >14 years (P = 0.04), male gender (P = 0.0004), smartphone use (P = 0.003), use of device >5 h (P = 0.0007) and mobile games >1 h/day (P = 0.0001) as independent risk factors for DES in children. Conclusion: There is an increased prevalence of DES among children in COVID era. Parents should be considerate about duration, type and distance of digital device use to avoid DES symptoms in children.

Assessment of eye fatigue caused by head-mounted displays using eye-tracking.

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.

Probabilistic assessment of visual fatigue caused by stereoscopy using dynamic Bayesian networks.

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.

Assessment of eye fatigue caused by 3D displays based on multimodal measurements.

With the development of 3D displays, user's eye fatigue has been an important issue when viewing these displays. There have been previous studies conducted on eye fatigue related to 3D display use, however, most of these have employed a limited number of modalities for measurements, such as electroencephalograms (EEGs), biomedical signals, and eye responses. In this paper, we propose a new assessment of eye fatigue related to 3D display use based on multimodal measurements. compared to previous works Our research is novel in the following four ways: first, to enhance the accuracy of assessment of eye fatigue, we measure EEG signals, eye blinking rate (BR), facial temperature (FT), and a subjective evaluation (SE) score before and after a user watches a 3D display; second, in order to accurately measure BR in a manner that is convenient for the user, we implement a remote gaze-tracking system using a high speed (mega-pixel) camera that measures eye blinks of both eyes; thirdly, changes in the FT are measured using a remote thermal camera, which can enhance the measurement of eye fatigue, and fourth, we perform various statistical analyses to evaluate the correlation between the EEG signal, eye BR, FT, and the SE score based on the T-test, correlation matrix, and effect size. Results show that the correlation of the SE with other data (FT, BR, and EEG) is the highest, while those of the FT, BR, and EEG with other data are second, third, and fourth highest, respectively.

Effectiveness of computerized risk assessment system on enhancing workers' occupational health and attitudes towards occupational health.

BACKGROUND: Efforts have been paid to lower the health risks associated with use of computers at the workplace. Computerized risk assessment systems are available in the market for adoption by companies. OBJECTIVES: The Display Screen Equipment Risk Assessment and Management System was designed for conducting risk assessment and providing intelligent-driven solutions for DSE-related occupational health problems. This report summarizes two consecutive research work conducted on evaluating its effect in reducing body discomfort and mental fatigue, and enhancing sedentary workers' occupational health. METHODS: Convenience sampling was adopted to recruit participants (111 participants for Study 1 and 75 participants for Study 2 who were randomly assigned to an immediate or a delayed intervention group. The intervention was using DSE RAM System to perform a risk assessment followed by an immediate modification of participant's workstation based on the recommendations generated by the System. Face to face interview was conducted and participants completed three sets of questionnaires right before the assessment and two weeks after the intervention. RESULTS: The results of Study 1 revealed that the DSE RAM System was effective for alleviating the discomfort and fatigue levels by rectifying the workstation-worker match. These mismatches were identified to be the heights of monitor, keyboard and chair with the workers. The results of Study 2 indicate that the System was specific for promoting participants to take more frequent rest breaks (OR: 3.65) and pay more attention to occupational safety and health information (OR: 3.90). In particular, the take frequent rest breaks behavior was found to predict decrease in discomfort in the eyes and mental fatigue (lack of energy). Nevertheless, there was no strong evidence on the use of the System can lead to immediate attitudinal changes towards occupational health and safety. CONCLUSION: The findings support the notion that workers' participation and integration of ergonomics into the management are important for successful implementation of occupational health programs. Together with educational and skill training sessions on occupational health at the workplace, the DSE RAM System offers a venue for implementing participatory ergonomics at the workplace.

The utility of strabismus in adults.

PURPOSE: To determine the utility (quality-of-life weight) associated with adult strabismus. METHODS: Time tradeoff utility values were measured in physician-conducted interviews with 140 adult patients with strabismus in a private practice setting. Patients also completed a questionnaire containing six items that rated the following aspects of disability: specific health problems, problems with tasks of daily living, problems with social interaction, self-image problems, concerns about the future, and job-related problems. Patients were characterized as presurgical or nonsurgical, and their diplopia and asthenopia were rated by the physician on a four-level scale. RESULTS: About 60% of all patients indicated willingness to trade part of their life expectancy in return for being rid of strabismus and its associated effects. The median utility was 0.93 (interquartile range, 0.83 to 1.0). A significantly smaller proportion (44%) of the nonsurgical patients (N = 41) appeared willing to trade time compared with surgical patients (68%; P = .009). Median utility in the presurgical patients was 0.90. Strong relationships were found between utility and the level of diplopia (P < .0001), and between utility and the level of asthenopia (P < .0001). Utility was correlated with all six disability ratings (all P < or = .00062). CONCLUSION: A majority of the patients interviewed would trade a portion of their life expectancy in return for being rid of strabismus and its associated effects. These results were validated by significant associations with diplopia, asthenopia, and disability.

Stereoacuity versus fixation disparity as indicators for vergence accuracy under prismatic stress.

BACKGROUND: Fixation disparity has been widely used as an indicator for vergence accuracy under prismatic stress. However, the targets used for measuring fixation disparity contain artificial features in that the fusional contours are thinned out. We considered that stereoacuity might be a preferable indicator of vergence accuracy, as stereo targets represent natural viewing conditions. METHODS: We measured fixation disparity with a computer adaptation of Ogle's test and stereoacuity with the automatic Freiburg Stereoacuity Test. Eight subjects were examined under increasing base-in and base-out prisms. RESULTS: The response of fixation disparity to prismatic stress revealed the curve types described by Ogle and Crone. All eight subjects reached a stereoscopic threshold below 10 arcsec. In seven subjects the stereoscopic threshold increased before double vision occurred. CONCLUSION: Our data suggest that stereoacuity is suitable to assess the range of binocular vision under prismatic stress. As stereoacuity bears the advantage over fixation disparity in that it can be measured without introducing artificial viewing conditions, we suggest exploring whether stereoacuity under prismatic stress would be more meaningful in the work-up of asthenopic patients than is fixation disparity.

A comparison of seven visual fatigue assessment techniques in three data-acquisition VDT tasks.

We compared 7 methods of measuring visual fatigue--accommodation power, visual acuity, pupil diameter, critical fusion frequency (CFF), eye movement velocity, subjective rating of visual fatigue, and task performance--for their sensitivity to visual load. In the experiment, 10 participants performed a monitoring task at 2 viewing distances, read articles under 2 levels of screen contrast, and tracked visual targets at 2 different speeds. The same measurement techniques, excluding pupil diameter and eye movement velocity, were compared by extending the task time from 20 to 60 min with the same VDT tasks to test for possible improvement in sensitivity. The results indicated that sensitivities of accommodation power, visual acuity, and CFF were greatly improved by a longer task period, but these 3 measurement techniques did not distinguish among tasks. Pupil diameter, eye movement velocity, and subjective rating of visual fatigue were sensitive in differentiating tracking from reading and monitoring tasks. Eye movement velocity and subjective rating were sensitive to the changes in target velocity of the tracking task. Although task performance was not directly comparable to other measurement techniques, it helped to ensure that participants maintained the same performance level by devoting more resources to the high-load conditions. Actual or potential applications of this research include using some of these assessment techniques for the design of adaptive displays.

[The integral assessment of subject symptoms for detecting chronic visual, motor and nonspecific fatigue in workers]. / Integral'naia otsenka sub''ektivnykh simptomov dlia vyiavleniia khronicheskogo zritel'nogo, dvigatel'nogo i nespetsificheskogo pereutomleniia rabotaiushchikh.

The authors present methods of integral evaluation of symptoms for diagnosis of chronic visual, locomotor and nonspecific fatigue in workers. Questionnaires and algorithms to treat them are incorporated into the methods that are to be used in hygienic regulation of work, particularly, to reveal comparative significance of work factors--visual efforts, physical hardiness and nerve strain.

[The dependence of the degree of visual fatigue on the shift duration in work with video terminals and an assessment of the efficacy of preventive measures]. / Zavisimost' stepeni zritel'nogo utomleniia ot smennoi dlitel'nosti raboty s videoterminalami i otsenka éffektivnosti mer ego profilaktiki.

Dynamic studies of visual capacity for work in individuals working with displays revealed decreased accommodation volume after the long concentration on the display. The total time of work with the display of more than 2h a day involved a decrease of the accommodation volume by 0.42-0.49 diopters and transitory myopia of 0.15-0.21 diopters, as well as increased self-appraisal of fatigue. The system of prophylactic measures including rest breaks, special exercises, massage was worked out and put into practice. Repeated study has proved the effectiveness of suggested measures.

Blepharoplasty. Indications and preoperative assessment.

Before performing a blepharoplasty, the surgeon must completely evaluate the patient to ascertain the proper diagnosis and indication for surgery and to identify any potentially complicating factors. The anatomy and physiology of the eyelids and lacrimal system must be understood in detail. A complete ophthalmologic examination should be performed to document preoperative decreased visual acuity or limited visual fields. The prevention of complications and the satisfaction of the patient are the goals of the blepharoplasty procedure. These require accurate assessment, proper preoperative diagnosis, and meticulous surgical technique.