Exploratory factor analysis and validity of the virtual reality symptom questionnaire and computer use survey.

The widespread use of virtual reality head-mounted-displays (HMDs) calls for a re-examination of the impact of prolonged exposure to fixed visual displays at close ocular proximity. The purpose of this study is to validate the Virtual Reality Symptoms Questionnaire (VRSQ), created to understand symptoms of prolonged HMDs use, and Computer Use Survey (CUS), created to assess general physical and visual discomfort symptoms. Participants (N = 100) recorded their general discomfort symptoms using the CUS, performed an interactive task using a HMD for thirty minutes, and then answered the CUS again along with the VRSQ. VRSQ, analysed using an exploratory factor analysis, indicated a clear two-factor solution, and demonstrated very good internal consistency (α = 0.873). The CUS, also analysed using an exploratory factor analysis, indicated a four-factor solution, and demonstrated good internal consistency (α = 0.838). Practitioner Summary: A quantitative-experimental study was conducted to explore the factor structure and validate both the Virtual Reality Symptoms Questionnaire (VRSQ), and the Computer Use Survey (CUS). Findings indicate the VRSQ and CUS are precise and accurate survey instruments for evaluating discomfort after VR-HMD use and the latter for computer use. Abbreviations: VRSQ: virtual reality symptom questionnaire; CUS: computer use survey; OLED: organic light-emitting diode; MSQ: pensacola motion symptom questionnaire; SSQ: simulator sickness questionnaire; 3 D: three-dimensional computer generated space; VR: virtual reality; VR-HMD: virtual reality head-mounted-display; HMDs: head-mounted-displays; EFA: exploratory factor analysis.

The Influence of Photophobia on Postural Control in Patients With Migraine.

BACKGROUND: People with migraine exhibit postural control impairments. These patients also have an increased light sensitivity due to the disease, and it remains during the headache-free period. It is currently unknown if increased lighting levels can alter the balance control, especially in individuals with visual hypersensitivity, such as migraineurs. This study aimed to assess the balance and photophobia of women with migraine and non-headache controls under different light conditions. METHODS: This cross-sectional study consisted of 14 women with migraine (mean ± SD 30.6 ± 8.1 years old) and 14 women without any kind of headache (mean ± SD 27.2 ± 2.8 years old) screened from a tertiary headache clinical hospital and the local community. Quiet standing balance was evaluated during bipodal and unipodal support, under 3 light conditions: ambient (AMB) - 270 lx, visual discomfort threshold (VDT) - 400 lx, and intense visual discomfort (IVD) - 2000 lx. Sway area of the center of pressure was processed and compared between groups. The association of migraine with the risk of presenting a greater imbalance in the discomfort lighting conditions was verified. RESULTS: Compared to the non-headache controls, the migraine group presented greater sway area in bipodal stance under the 3 light conditions (mean difference (95% CI)): AMB 0.81 cm2 (0.19 to 1.43), P = .011; VDT 3.17 cm2 (0.74 to 5.60), P = .001; IVD 5.56 cm2 (2.75 to 8.37), P < .0001. Within-subject analysis showed increased sway area in bipodal stance among all lighting conditions for the migraine group only (mean difference (95% CI)): VDT-AMB 2.20 cm2 (0.23 to 4.18), P = .024; IVD-AMB 4.50 cm2 (2.38 to 6.62), P < .0001, IVD-VDT 2.29 cm2 (0.57 to 4.01), P = .005. The Prevalence Ratio (PR) analysis showed that migraine was associated with the risk of presenting greater imbalance in both bipodal and unipodal standing conditions for both VDT (PR value (95% CI) - bipodal: PR = 4.00 (1.02 to 15.59), P = .045; unipodal: PR = 4.00 (1.43 to 11.15), P = .008), and the IVD (bipodal: PR = 3.33 (1.13 to 9.58), P = .025; unipodal: PR = 5.50 (1.48 to 20.42), P = .010) lighting conditions. CONCLUSION: Photophobia might be a disturbing factor that worsens the balance of patients with migraine during the quiet standing posture.

Exploration of anomalous perceptual experiences in migraine between attacks using the Cardiff Anomalous Perceptions Scale.

Distortions in sensory experiences that precede a migraine attack have been extensively documented, the most well-known being the visual aura. Distortions in the experience of other senses are also reported as part of an aura, albeit less frequently, together with changes in the perception or ownership of the body or body parts. There are many examples of differences in aspects of visual perception between migraine and control groups, between attacks, but not as much on unusual experiences involving other senses, the sense of the body or the experience of the environment. Seventy-seven migraine (33 with aura) and 74 control participants took part. Anomalous perceptions were experienced by both migraine and control groups, but more with migraine experienced them and rated them as more distressing, intrusive and frequent. Associations with reports of visual triggers of migraine and visual discomfort are presented. This study is the first to show relationships between these factors.

Surgical implications of 3D vs 2D endoscopic ear surgery: a case-control study.

PURPOSE: To compare 3D to 2D technology in endoscopic ear surgery (EES); to report surgeons' feedback on the use of 3D in EES; to describe the operative setting for 3D EES. METHODS: A case-control study on EES was performed at a tertiary university center. All consecutive cases of 3D EES (case group) were matched to a control group operated with the standard 2D technique. Data on surgical approach, type of surgery, operative time, outcomes, and complications were compared between the two groups. After each surgery, the operating surgeons were asked to give a feedback on the use of 3D endoscopy, filling in a questionnaire based on 5-point Likert scales. RESULTS: None of the 3D procedures was switched to 2D. Nor intraoperative or long-term complications were recorded. The operative time was similar in both groups. Postoperative hearing function did not show any statistically significant difference between 3 and 2D patients. Ninety-six percent of participants agreed or strongly agreed on better views of anatomy and pathology with the 3D technique. Discomfort induced by 3D vision was rarely reported. CONCLUSION: Surgical and functional results from EES respectively performed with 3D and 2D systems are overall similar, suggesting that both techniques are safe and effective. According to the surgeons' feedback, 3D provides better depth perception and improved view of anatomy and pathology. Several surgeons are willing to use the 3D system for future EES. To guarantee the best 3D EES experience, the setting in the operating room plays a crucial role.

Convergence insufficiency and accommodative insufficiency in children.

PURPOSE: Convergence and accommodative insufficiency represent the main cause of complaints during close visual work and can reduce visual performance and comfort. Knowing their prevalence among schoolchildren is fundamental to define strategies for action. The purpose of this study was to estimate the frequency of these conditions in children in 5th and 6th school years in inland Portugal and to assess the impact that each visual condition has on their quality of life, based on the level of visual symptoms. METHODS: a cross-sectional study was carried out with children enrolled in the 5th and 6th school years. 372 children (192 girls) were assessed, with average ages of 10.9 ± 0.9 years. Refractive error and binocular vision assessment, integrating accommodative parameters, were used to analyse the visual condition. Symptoms were quantified using the Portuguese version of the CISS (Convergence Insufficiency Symptom Survey). RESULTS: The prevalence of definite Convergence Insufficiency (CI) in the children assessed was 2%. A prevalence of 6,8% could be considered if clinically significant CI (high suspect and definite categories) cases are accounted. In relation to Accommodative Insufficiency (AI), a frequency rate of 10% was recorded, with 3% of the evaluated children presenting AI and CI simultaneously. The symptoms score was higher in AI than in CI. CONCLUSIONS: A frequency of approximately 10% was found for each one of the visual syndromes, and it was verified that visual discomfort is common among teenagers who carry these conditions. In cases of asthenopia, such as headaches and loss of concentration, associated with near vision activities, there is a requirement to evaluate the quality of binocular vision.

Effects of disparity on visual discomfort caused by short-term stereoscopic viewing based on electroencephalograph analysis.

BACKGROUND: Discomfort evoked by stereoscopic depth has been widely concerned. Previous studies have proposed a comfortable disparity range and considered that disparities exceed this range would cause visual discomfort. Brain activity recordings including Electroencephalograph (EEG) monitoring enable better understanding of perceptual and cognitive processes related to stereo depth-induced visual comfort. METHODS: EEG data was collected using a stereo-visual evoked potential (VEP) test system by providing visual stimulus to subjects aged from 21 to 25 with normal stereoscopic vision. For each type of visual stimulus, data were processed using directed transfer function (DTF) and adaptive directed transfer function (ADTF) in combination with subjective feedbacks (comfort or discomfort). The topographies of information flow were constructed to compare responses stimulated by different stereoscopic depth, and to determine the difference in comfort and discomfort situations upon stimulation with same stereoscopic depth. RESULTS: Based on EEG analysis results, we found that the occipital P270 was moderately related to the disparity. Moreover, the ADTF of P270 showed that the information flows at frontal lobe and central-parietal lobe changed when stimulation with different stereoscopic depth applied. As to the stereo images with same stereoscopic depth, the DTF outflows at the temporal and temporal-parietal lobes in δ band, central and central-parietal lobes in α and θ bands, and the comparison of inflows in these three bands could be considered as discriminated indexes for matching the stereoscopic effect with viewers' comfort or discomfort state impacted by disparity. The subjective feedbacks indicated that the comfort judgments remained as a result of cumulative effect. CONCLUSIONS: This study proposed a short-term stereo-VEP experiment that shorted the duration of each stimulus in the experimental scheme to minimize the interference from other factors except the disparity. The occipital P270 had a mid-relevance to the disparity and its ADTF showed the affected areas when viewers are receiving stimulations with different disparities. DTF could be considered as discriminated indexes for matching the stereoscopic effect with viewers' comfort or discomfort state induced by disparity. This study proposed a preferable experiment to observe the single effect of disparity and provided an intuitive and easy-to-read result in a more convenient manner.

Steady-state VEP responses to uncomfortable stimuli.

Periodic stimuli, such as op-art, can evoke a range of aversive sensations included in the term visual discomfort. Illusory motion effects are elicited by fixational eye movements, but the cortex might also contribute to effects of discomfort. To investigate this possibility, steady-state visually evoked responses (SSVEPs) to contrast-matched op-art-based stimuli were measured at the same time as discomfort judgements. On average, discomfort reduced with increasing spatial frequency of the pattern. In contrast, the peak amplitude of the SSVEP response was around the midrange spatial frequencies. Like the discomfort judgements, SSVEP responses to the highest spatial frequencies were lowest amplitude, but the relationship breaks down between discomfort and SSVEP for the lower spatial frequency stimuli. This was not explicable by gross eye movements as measured using the facial electrodes. There was a weak relationship between the peak SSVEP responses and discomfort judgements for some stimuli, suggesting that discomfort can be explained in part by electrophysiological responses measured at the level of the cortex. However, there is a breakdown of this relationship in the case of lower spatial frequency stimuli, which remains unexplained.

Accommodative changes after SMILE for moderate to high myopia correction.

BACKGROUND: To investigate accommodative response and accommodative lag changes after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction. METHODS: A total of 32 eyes of 32 patients with no strabismus who underwent SMILE were enrolled in this prospective clinical study. The accommodative response was obtained viewing monocularly with spherical equivalent refractive error corrected, using an open-field autorefractor at different stimulus levels (2.00D, 2.50D, 3.00D, 4.00D and 5.00D) for the right eye before a standard SMILE surgery and at 1-month follow-up after surgery. RESULTS: The mean age of the patients were 23.34 ± 2.90 years and the mean preoperative manifest refraction spherical equivalent was -5.74 ± 1.98 diopters. Significant differences were detected in both preoperative and postoperative accommodative responses to different stimulus levels (P < 0.001). Multiple linear regression model analysis revealed preoperative manifest refractive spherical equivalent (P = 0.006) and preoperative accommodative lag (P = 0.04) showed a significant impact on postoperative accommodative lag. CONCLUSIONS: This is the first report of accommodative changes after SMILE. Our preliminary results showed that a decrease in postoperative accommodative lag that might be related to the relief of the visual discomfort symptom.

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

PURPOSE: The prevalence of work-related upper extremity musculoskeletal disorders and visual symptoms reported in the USA has increased dramatically during the past two decades. This study examined the factors of computer use, workspace design, psychosocial factors, and organizational ergonomics resources on musculoskeletal and visual discomfort and their impact on the safety and health of computer work employees. METHODS: A large-scale, cross-sectional survey was administered to a US manufacturing company to investigate these relationships (n = 1259). Associations between these study variables were tested along with moderating effects framed within a conceptual model. RESULTS: Significant relationships were found between computer use and psychosocial factors of co-worker support and supervisory relations with visual and musculoskeletal discomfort. Co-worker support was found to be significantly related to reports of eyestrain, headaches, and musculoskeletal discomfort. Supervisor relations partially moderated the relationship between workspace design satisfaction and visual and musculoskeletal discomfort. CONCLUSION: This study provides guidance for developing systematic, preventive measures and recommendations in designing office ergonomics interventions with the goal of reducing musculoskeletal and visual discomfort while enhancing office and computer workers' performance and safety.

Visual discomfort while watching stereoscopic three-dimensional movies at the cinema.

PURPOSE: This study investigates discomfort symptoms while watching Stereoscopic three-dimensional (S3D) movies in the 'real' condition of a cinema. In particular, it had two main objectives: to evaluate the presence and nature of visual discomfort while watching S3D movies, and to compare visual symptoms during S3D and 2D viewing. METHOD: Cinema spectators of S3D or 2D films were interviewed by questionnaire at the theatre exit of different multiplex cinemas immediately after viewing a movie. RESULTS: A total of 854 subjects were interviewed (mean age 23.7 ± 10.9 years; range 8-81 years; 392 females and 462 males). Five hundred and ninety-nine of them viewed different S3D movies, and 255 subjects viewed a 2D version of a film seen in S3D by 251 subjects from the S3D group for a between-subjects design for that comparison. Exploratory factor analysis revealed two factors underlying symptoms: External Symptoms Factors (ESF) with a mean ± S.D. symptom score of 1.51 ± 0.58 comprised of eye burning, eye ache, eye strain, eye irritation and tearing; and Internal Symptoms Factors (ISF) with a mean ± S.D. symptom score of 1.38 ± 0.51 comprised of blur, double vision, headache, dizziness and nausea. ISF and ESF were significantly correlated (Spearman r = 0.55; p = 0.001) but with external symptoms significantly higher than internal ones (Wilcoxon Signed-ranks test; p = 0.001). The age of participants did not significantly affect symptoms. However, females had higher scores than males for both ESF and ISF, and myopes had higher ISF scores than hyperopes. Newly released movies provided lower ESF scores than older movies, while the seat position of spectators had minimal effect. Symptoms while viewing S3D movies were significantly and negatively correlated to the duration of wearing S3D glasses. Kruskal-Wallis results showed that symptoms were significantly greater for S3D compared to those of 2D movies, both for ISF (p = 0.001) and for ESF (p = 0.001). CONCLUSIONS: In short, the analysis of the symptoms experienced by S3D movie spectators based on retrospective visual comfort assessments, showed a higher level of external symptoms (eye burning, eye ache, tearing, etc.) when compared to the internal ones that are typically more perceptual (blurred vision, double vision, headache, etc.). Furthermore, spectators of S3D movies reported statistically higher symptoms when compared to 2D spectators.

Photosensitivity in mild traumatic brain injury (mTBI): a retrospective analysis.

PRIMARY OBJECTIVE: To determine whether photosensitivity (PS) changes over time and, if so, what factors may be related to the change; furthermore, to determine whether tint density changes over time, all in mild traumatic brain injury (mTBI). DESIGN AND METHODS: A retrospective analysis of 62 patient records (aged 18-40 years) with mTBI and PS was conducted. All charts were obtained from the SUNY/College of Optometry clinics from 2004-2011. RESULTS: Fifty per cent demonstrated reduced PS over time, with most occurring after year 1 post-injury (40%). Promotion of PS reduction appears to be associated with the lack of spectacle tint usage (p = 0.01) and the use of contact lenses (p = 0.03). Inhibition of PS reduction appears to be associated with tinted lenses (p = 0.06), hyperacusis (p = 0.03), dry eye (p = 0.04), migraines (p = 0.03) and loss of consciousness at the time of injury (p = 0.05). Concerning tint density changes over time, 71% (p = 0.002) maintained the same degree over time, while 27% (p = 0.002) reduced and 2% waxed and waned. CONCLUSION: Neural adaptation to PS appears to be a long-term process. Tint usage may act to inhibit this adaptive process, while the use of contact lenses may act to promote it. These findings may provide guidance in the clinical management of photosensitivity in the mTBI population.

Abstracts of Scottish Vision Group 2023 Meeting.

Scottish Vision Group has become a yearly event for vision scientists based in Scotland since its inception in 2001. Each year, the conference is hosted at a different location and organised by a different team. The 2023 SVG meeting was hosted in the city of Dundee by Abertay University. Delegates travelled from the United Kingdom, Europe and beyond. The meeting started with a roundtable panel discussion sponsored by Meta Reality Labs. The roundtable, titled The Past, Present and Future of Visual Search, was organised and presented by Árni Kristjánsson (Iceland), Ioan Smart (Abertay) and Ian Thornton (Malta). The MDPI Keynote lecture was introduced by Professor Andrew Parker (Oxford University and Otto-von-Guericke University in Magdeburg, Germany) and presented by Prof. Timothy Ledgeway (Nottingham) on sensory eye dominance and plasticity in adult binocular vision. The remaining two days of the conference hosted a wide range of talks on topics ranging from insect navigation to visual illusions, facial recognition and binocular coding. The Saturday evening saw a special event where delegates explored the sensory properties of a range of single-malt whiskies. Here, we present a selection of abstracts for the various talks and posters.

Color and spatial frequency are related to visual pattern sensitivity in migraine.

OBJECTIVE: To assess the potential for particular colors to alleviate visual discomfort when people with migraine view repetitive geometric or striped patterns. BACKGROUND: Visual stimuli, such as flicker, glare, or stripes, can trigger migraine and headache. They can also elicit feelings of discomfort and aversion. There are reports that color can be used to decrease the experience of discomfort and reduce migraine frequency. DESIGN/METHODS: Five sets of striped patterns (3, 12 cycles per degree [cpd]) were created using cardinal colors tailored to selectively stimulate the early visual pathways: achromatic (black/white), tritan (black/purple, black/yellow), protan/deutan (black/red, black/green). All had the same high luminance contrast (0.9 Michelson contrast). Twenty-eight migraine (14 migraine with aura, 14 migraine without aura) and 14 control participants rated the discomfort and described the distortions seen in these patterns. They were also assessed for visual migraine/headache triggers, contrast sensitivity, color vision, acuity, stereopsis, visual discomfort from reading, and dyslexia. RESULTS: In the migraine groups, a comparable number of illusions were seen with the 3 and 12 cpd achromatic gratings, whereas in the control group the greatest number was seen with the 3 cpd grating. In the migraine groups only, all 4 colors reduced, to some extent, the number of illusions and 2 decreased the discomfort, particularly for the 12 cpd gratings. There were significant group differences for contrast sensitivity, reported visual migraine/headache triggers, and the visual discomfort scale. There were a few significant correlations between the different measures, notably between the achromatic visual discomfort measures and reports of visual migraine triggers. CONCLUSIONS: Color, independent of luminance or particular color contrasts, can have therapeutic effects for people with visually triggered migraine as it can reduce the number of perceived illusions when viewing stripes or text. The effect was not color-specific and was greatest for the 12 cpd gratings. Given the significant associations between the achromatic discomfort measures and reports of visual triggers, and the lack of significant associations between the chromatic discomfort measures and reports of visual triggers, further research is recommended to explore the potential to reduce the number of visually triggered migraines with color in addition to alleviating visual discomfort.

Heterophoria adaptation during the viewing of 3D stereoscopic stimuli.

PURPOSE: In this experiment two hypotheses were tested. The first hypothesis was that viewing 3D stereoscopic stimuli which are located geometrically beyond the screen on which the images are displayed would induce exophoric heterophoria (phoria) changes (adaptation). The second hypothesis was that participants whose phoria changed as a consequence of adaptation during the viewing of the stereoscopic stimuli would experience less visual discomfort than people whose phoria did not adapt. METHODS: Twenty participants aged between 19 and 45 were recruited to play a computer game in 3D and 2D conditions for 20 min each. Heterophoria was measured before and after viewing the stimuli, and visual discomfort was assessed by questionnaire on both occasions. RESULTS: Statistically significant changes in heterophoria were found in the 3D conditions (p = 0.007), but not in the 2D conditions (p = 0.16). The difference between the two conditions was statistically significant (p = 0.035). On average, there were also significant differences in visual discomfort between pre and post viewing, for both 2D and 3D conditions, however not everyone reported experiencing discomfort. The sample was then divided into groups, those who had reported an increase in discomfort whilst viewing 3D stimuli, and those who had not. No significant differences in heterophoria, or heterophoria change, were found between these two groups. CONCLUSIONS: The present study has shown that heterophoria can change as a result of viewing 3D stereoscopic stimuli, a change which is similar to prism adaptation. There was appreciable variability in the magnitude of this adaptation between individuals, but there was no correlation between the heterophoria change and visual discomfort.

The relationship between visual discomfort and cortical excitability in cone-opponent stimuli.

Increased colour contrast can induce visual discomfort, but there is little research on the effect of hue. Colour is processed via one or more information streams or channels. We hypothesized that hues which activate more than one channel would induce greater visual discomfort, as they will demand greater neural resources. Normally-sighted young observers made discomfort judgments of isoluminant stimuli of varying hue and contrast whilst EEG was recorded. As predicted, stimuli recruiting more than one channel were more uncomfortable, and this increased with contrast. Uncomfortable stimuli showed increased N2 event-related potentials and decreased alpha-band oscillations, potentially indicating increased neural excitability. This is evidence that increased neural responses are related to visual discomfort for chromatic stimuli. Furthermore, it suggests that the origins of visual discomfort are in early visual areas, when colour is represented in a cone-opponent space, rather than later areas where colour representation is determined by perceptual similarity.

A comparison of visual discomfort experienced by surgeons in wireless versus conventional endoscopy in laparoscopic surgery.

Background: This study was performed to introduce a new wireless endoscopic system. Research and development were based on fifth-generation transmission technology. Eye symptoms and visual discomfort induced by the novel endoscopic system were compared with those induced by the conventional endoscopic system before and during laparoscopic pelvic surgery. Materials and methods: Twenty surgeons successfully conducted laparoscopic pelvic surgeries using a conventional endoscopic system and a wireless endoscopic system. Subjective and objective data were measured to evaluate visual discomfort before and 2 hours after surgery. Results: In the conventional endoscopic and wireless endoscopic system groups, no significant differences were found in the presurgical or postsurgical questionnaires. In both groups, tear film breakup times significantly decreased after surgery. However, after comparing the 2 groups, no statistically significant difference was found. Conclusions: Compared with the conventional endoscopic system, the novel wireless endoscopic system does not cause additional visual discomfort for experienced surgeons.

Influence of prismatic effect due to decentration of optical center in ophthalmic lens.

Background and Aims: Induced prismatic effects due to poor fitting spectacle frames is a common problem, seen in most of the spectacle wearers and this improper fitting is often due to optical center demarcation on lenses and this error causes asthenopic symptoms and diplopia. However, these errors are most common in developing countries due to lack of awareness, hence a standardized regulation is required. The current study aimed to estimate the amount of prismatic effect that is induced due to the decentration of an optical center in ophthalmic lens. Methods: A quantitative cross-sectional study was conducted in single vision spectacle wearers (N = 120) with a mean age of 25 ± 5 years. The pupillometric evaluation was performed to mark the pupil center on the spectacle lens. A lensometry evaluation was done to mark the optic center of the spectacle lens. A comparison was made to note whether the optic center is aligned with pupillary center. Objective assessment was performed through Prentice's rule (P = cF) and subjective symptoms were assessed through a validated visual comfort questionnaire. Results: In this sample, around 57% of the individual with single vision glasses were not looking through the optic center and experiencing induced prismatic effect of -0.7 to 0.6 prism diopter, with mean decentration of 3.5 mm. Forty percent of the individuals with misaligned optic center showed asthenopic symptoms and visual discomfort. Conclusion: Optometrist should check quality of dispensing and visual performance before handing over the newly dispensed glasses to the patients.

Temporal effects of an original myopia song on school children's myopia and awareness: a 3-year prospective study.

CLINICAL RELEVANCE: Raising children's myopia prevention awareness and behaviour tends to exhibits a protective effect against myopia among schoolchildren. BACKGROUND: To investigate the effect of an original myopia song in raising school children's awareness of healthier eye use behaviour and on myopia prevention. METHODS: In this prospective randomised control study, two groups of students from one primary schools in Jiangxi, China, were enrolled and monitored from grade 3 to grade 6 (2016-2019). The primary outcome was the change in axial length (AL) after the intervention. Secondary outcomes included changes in spherical equivalent refraction (SER), near work and outdoor time, corrected near and distant visual acuity, visual discomfort score (VDS) and accommodative lag. RESULTS: Four hundred students (193 females, 48.25%) aged 9.3 (range 8-10) years with emmetropia to moderate myopia were enrolled. Children in the myopia song group had a significantly shorter AL and less myopic refractive change than those in the control group (p = 0.04 and 0.02, respectively). Compared with the control group, children in the myopia song group spent less time on near work and more time outdoors (p = 0.04 and 0.04, respectively). At the final follow-up, the proportion of children with myopia was significantly lower in the myopia song group (30.5%) than in the control group (41%) (p = 0.03). No significant differences were found for the secondary outcomes, including corrected near and distant visual acuity, VDS and accommodative lag. CONCLUSIONS: An original myopia song performed twice daily in primary schools appeared to have a modest effect on myopia control among school-aged children by changing their lifestyles in the long term.

A mechanistic account of visual discomfort.

Much of the neural machinery of the early visual cortex, from the extraction of local orientations to contextual modulations through lateral interactions, is thought to have developed to provide a sparse encoding of contour in natural scenes, allowing the brain to process efficiently most of the visual scenes we are exposed to. Certain visual stimuli, however, cause visual stress, a set of adverse effects ranging from simple discomfort to migraine attacks, and epileptic seizures in the extreme, all phenomena linked with an excessive metabolic demand. The theory of efficient coding suggests a link between excessive metabolic demand and images that deviate from natural statistics. Yet, the mechanisms linking energy demand and image spatial content in discomfort remain elusive. Here, we used theories of visual coding that link image spatial structure and brain activation to characterize the response to images observers reported as uncomfortable in a biologically based neurodynamic model of the early visual cortex that included excitatory and inhibitory layers to implement contextual influences. We found three clear markers of aversive images: a larger overall activation in the model, a less sparse response, and a more unbalanced distribution of activity across spatial orientations. When the ratio of excitation over inhibition was increased in the model, a phenomenon hypothesised to underlie interindividual differences in susceptibility to visual discomfort, the three markers of discomfort progressively shifted toward values typical of the response to uncomfortable stimuli. Overall, these findings propose a unifying mechanistic explanation for why there are differences between images and between observers, suggesting how visual input and idiosyncratic hyperexcitability give rise to abnormal brain responses that result in visual stress.

Assessment of 3D Visual Discomfort Based on Dynamic Functional Connectivity Analysis with HMM in EEG.

Stereoscopic displays can induce visual discomfort despite their wide application. Electroencephalography (EEG) technology has been applied to assess 3D visual discomfort, because it can capture brain activities with high temporal resolution. Previous studies explored the frequency and temporal features relevant to visual discomfort in EEG data. Recently, it was demonstrated that functional connectivity between brain regions fluctuates with time. However, the relationship between 3D visual discomfort and dynamic functional connectivity (DFC) remains unknown. Although HMM showed advantages over the sliding window method in capturing the temporal fluctuations of DFC at a single time point in functional magnetic resonance imaging (fMRI) data, it is unclear whether HMM works well in revealing the time-varying functional connectivity of EEG data. In this study, the hidden Markov model (HMM) was introduced to DFC analysis of EEG data for the first time and was used to investigate the DFC features that can be used to assess 3D visual discomfort. The results indicated that state 2, with strong connections between electrodes, occurred more frequently in the early period, whereas state 4, with overall weak connections between electrodes, occurred more frequently in the late period for both visual comfort and discomfort stimuli. Moreover, the 3D visual discomfort stimuli caused subjects to stay in state 4 more frequently, especially in the later period, in contrast to the 3D visual comfort stimuli. The results suggest that the increasing occurrence of state 4 was possibly related to visual discomfort and that the occurrence frequency of state 4 may be used to assess visual discomfort.