Stereopsis assessment at multiple distances with an iPad application

[EN] We present a new application for iPad for screening stereopsis at multiple distances that allows testing up to ten levels of stereoacuity at each distance. Our approach is based on a random dot stereogram viewable with anaglyph spectacles. Sixty-five subjects with no ocular diseases, wearing their habitual correction were measured at 3 m and 0.5 m. Results were compared with a standard stereoscopic test (TNO). We found not statistically significant differences between both tests, but our method achieved higher reproducibility. Applications in visual screening programs and to design and use of 3D displays, are suggested. (C) 2017 Elsevier B.V. All rights reserved.This work was supported by the Ministerio de Economia y Competitividad and FEDER (Grant DPI2015-71256-R) and by the Generalitat Valenciana (Grant PROMETEOII-2014-072), Spain. D. Montagud acknowledges financial support from Universitat Politecnica de Valencia (PAID-01-16)Rodríguez-Vallejo, M.; Ferrando, V.; Montagud-Martínez, D.; Monsoriu Serra, JA.; Furlan, WD. (2017). Stereopsis assessment at multiple distances with an iPad application. Displays. 50:35-40. https://doi.org/10.1016/j.displa.2017.09.001S35405

Prevalence of Ametropia, Amblyopia and visual impairment in schoolchildren in Ireland

Background: Uncorrected refractive error is an avoidable cause of visual impairment (Naidoo et al., 2016). Currently, there is a lack of adequate data on eye and vision disorders in schoolchildren in Ireland. Accurate prevalence estimates of refractive error and vision disorders are necessary to determine their impact on public health and to assess the need for interventions (McCarty and Taylor, 2000). Purpose: This study reports the prevalence of ametropia, presenting visual impairment, amblyopia and provides population norms for ocular biometric measures in schoolchildren in Ireland. Links between refractive error and demographic and lifestyle factors were investigated. The impact of poor presenting vision, on participants’ educational performance, was also examined. Methods: The Ireland Eye Study examined 1,626 children (881 boys, 745 girls) in two age groups, 6-7 years (728) and 12-13 years (898), in the Republic of Ireland (henceforth Ireland) between June 2016 and January 2018. Participating schools were selected by stratified random sampling, representing a mix of school type (primary/post-primary), location (urban/rural) and socioeconomic status (disadvantaged/advantaged). Parents completed a questionnaire which provided information on participants’ lifestyle and participants’ school performance. Examination included monocular logMAR visual acuity (both presenting with spectacles if worn and through a pinhole), cycloplegic auto-refraction (Cyclopentolate Hydrochloride 1%), non-contact ocular biometry (IOLMaster), and ocular alignment (cover test). Results: The prevalence of myopia (≤-0.50 D), hyperopia (≥+2.00 D), and astigmatism (≥1.00 DC) in 6-7-year-olds was 3.3%, 25.0%, 19.2%, respectively, and amongst 12-13-year-old children, 19.9%, 8.9% and 15.9%, respectively. Astigmatism axes were mostly with-the-rule (80.3%). The prevalence of presenting visual impairment in the “better ii eye” (≥0.3logMAR, with spectacles, if worn) was 3.7% amongst younger and 3.4% amongst older participants and associated with Traveller and non-White ethnicity. Amblyopia prevalence (pin-hole visual acuity ≥0.3logMAR plus an amblyogenic factor), was high (6-7 years 5.5%, 12-13 years 3.7%) compared to other studies. Amblyopia prevalence was primarily due to uncorrected refractive error. Compliance with spectacle wear, socioeconomic disadvantage and sedentary lifestyle were also contributing factors. Factors associated with myopia included age group, ethnicity, screen-time, time spent outdoors during daylight, obesity and sedentary lifestyle. Astigmatism was significantly associated with visual impairment and amblyopia. Time spent outdoors during daylight in summer was associated with a significantly less myopic SER and shorter axial length in White participants. Poor educational performance was associated with presenting visual impairment and amblyopia

Perspective Preserving Solution for Quasi-Orthoscopic Video See-Through HMDs

In non-orthoscopic video see-through (VST) head-mounted displays (HMDs), depth perception through stereopsis is adversely affected by sources of spatial perception errors. Solutions for parallax-free and orthoscopic VST HMDs were considered to ensure proper space perception but at expenses of an increased bulkiness and weight. In this work, we present a hybrid video-optical see-through HMD the geometry of which explicitly violates the rigorous conditions of orthostereoscopy. For properly recovering natural stereo fusion of the scene within the personal space in a region around a predefined distance from the observer, we partially resolve the eye-camera parallax by warping the camera images through a perspective preserving homography that accounts for the geometry of the VST HMD and refers to such distance. For validating our solution; we conducted objective and subjective tests. The goal of the tests was to assess the efficacy of our solution in recovering natural depth perception in the space around said reference distance. The results obtained showed that the quasi-orthoscopic setting of the HMD; together with the perspective preserving image warping; allow the recovering of a correct perception of the relative depths. The perceived distortion of space around the reference plane proved to be not as severe as predicted by the mathematical models

Ability of head-mounted display technology to improve mobility in people with low vision: a systematic review

Purpose: The purpose of this study was to undertake a systematic literature review on how vision enhancements, implemented using head-mounted displays (HMDs), can improve mobility, orientation, and associated aspects of visual function in people with low vision. Methods: The databases Medline, Chinl, Scopus, and Web of Science were searched for potentially relevant studies. Publications from all years until November 2018 were identified based on predefined inclusion and exclusion criteria. The data were tabulated and synthesized to produce a systematic review. Results: The search identified 28 relevant papers describing the performance of vision enhancement techniques on mobility and associated visual tasks. Simplifying visual scenes improved obstacle detection and object recognition but decreased walking speed. Minification techniques increased the size of the visual field by 3 to 5 times and improved visual search performance. However, the impact of minification on mobility has not been studied extensively. Clinical trials with commercially available devices recorded poor results relative to conventional aids. Conclusions: The effects of current vision enhancements using HMDs are mixed. They appear to reduce mobility efficiency but improved obstacle detection and object recognition. The review highlights the lack of controlled studies with robust study designs. To support the evidence base, well-designed trials with larger sample sizes that represent different types of impairments and real-life scenarios are required. Future work should focus on identifying the needs of people with different types of vision impairment and providing targeted enhancements. Translational Relevance: This literature review examines the evidence regarding the ability of HMD technology to improve mobility in people with sight loss

Explaining Self-Motion Perception using Virtual Reality in Patients with Ocular Disease

Safe mobility requires accurate object and self-motion perception. This involves processing retinal motion generated by optic flow (which change with eye and head movements) and correctly integrating this with vestibular and proprioceptive cues. Poor sensory feedback of self-motion can lead to increased risks of accidents which impacts quality of life. This is further problematic for those with visual deficits, such as central or peripheral vision loss or impaired binocular vision. The expansion of healthcare into using virtual reality (VR) has allowed the assessment of sensory and motor performance in a safe environment. An advantage of VR is its ability to generate vection (perceived illusory self-motion) and presence (sense of being ‘there’). However, a limitation is the potential to develop cybersickness. Initially, the project examined how binocular vision influences vection in a virtual environment. Observers with or without stereopsis (ability to judge depth binocularly) were asked to compare their perceptual experiences based on psychophysical judgements of magnitude estimation. The findings suggest that the absence of stereopsis impairs accurate judgement of self-motion and reduces perceived presence, however, it was protective for cybersickness. The project then examined the impact of central and peripheral vision loss on self-motion perception by comparing those with age-related macular degeneration (AMD) and glaucoma respectively. Effects of these visual deficits on sensory conflicts involving visual-vestibular interactions was then assessed. Sensory conflict was imposed by altering the gain of simulated head linear head position and angular orientation to be either compatible or incompatible with head movement in two separate experiments. Fixation was used to control gaze during changes in angular head orientation. Vection and presence was higher in those with AMD, compared with those with glaucoma, indicating the importance of regional specificity in visual deficits on self-motion perception. Across studies, vection and presence were predominantly visually mediated despite changes in visual-vestibular sensory conflict. The vestibular system, however, appeared to play a larger role in developing cybersickness. The altered perception of self-motion may worsen mobility, particularly with disease progression. We therefore provide a framework and recommendations for a multidisciplinary patient-centric model of care to maximise quality of life

A Neurophysiologic Study Of Visual Fatigue In Stereoscopic Related Displays

Two tasks were investigated in this study. The first study investigated the effects of alignment display errors on visual fatigue. The experiment revealed the following conclusive results: First, EEG data suggested the possibility of cognitively-induced time compensation changes due to a corresponding effect in real-time brain activity by the eyes trying to compensate for the alignment. The magnification difference error showed more significant effects on all EEG band waves, which were indications of likely visual fatigue as shown by the prevalence of simulator sickness questionnaire (SSQ) increases across all task levels. Vertical shift errors were observed to be prevalent in theta and beta bands of EEG which probably induced alertness (in theta band) as a result of possible stress. Rotation errors were significant in the gamma band, implying the likelihood of cognitive decline because of theta band influence. Second, the hemodynamic responses revealed that significant differences exist between the left and right dorsolateral prefrontal due to alignment errors. There was also a significant difference between the main effect for power band hemisphere and the ATC task sessions. The analyses revealed that there were significant differences between the dorsal frontal lobes in task processing and interaction effects between the processing lobes and tasks processing. The second study investigated the effects of cognitive response variables on visual fatigue. Third, the physiologic indicator of pupil dilation was 0.95mm that occurred at a mean time of 38.1min, after which the pupil dilation begins to decrease. After the average saccade rest time of 33.71min, saccade speeds leaned toward a decrease as a possible result of fatigue on-set. Fourth, the neural network classifier showed visual response data from eye movement were identified as the best predictor of visual fatigue with a classification accuracy of 90.42%. Experimental data confirmed that 11.43% of the participants actually experienced visual fatigue symptoms after the prolonged task

A Systematic Review of Extended Reality (XR) for Understanding and Augmenting Vision Loss

Over the past decade, extended reality (XR) has emerged as an assistive technology not only to augment residual vision of people losing their sight but also to study the rudimentary vision restored to blind people by a visual neuroprosthesis. To make the best use of these emerging technologies, it is valuable and timely to understand the state of this research and identify any shortcomings that are present. Here we present a systematic literature review of 227 publications from 106 different venues assessing the potential of XR technology to further visual accessibility. In contrast to other reviews, we sample studies from multiple scientific disciplines, focus on augmentation of a person's residual vision, and require studies to feature a quantitative evaluation with appropriate end users. We summarize prominent findings from different XR research areas, show how the landscape has changed over the last decade, and identify scientific gaps in the literature. Specifically, we highlight the need for real-world validation, the broadening of end-user participation, and a more nuanced understanding of the suitability and usability of different XR-based accessibility aids. By broadening end-user participation to early stages of the design process and shifting the focus from behavioral performance to qualitative assessments of usability, future research has the potential to develop XR technologies that may not only allow for studying vision loss, but also enable novel visual accessibility aids with the potential to impact the lives of millions of people living with vision loss

The sweet spot: How people trade off size and definition on mobile devices

Mobile TV can deliver up-to-date content to users on the move. But it is currently unclear how to best adapt higher resolution TV content. In this paper, we describe a laboratory study with 35 participants who watched short clips of different content and shot types on a 200ppi PDA display at a resolution of either 120x90 or 168x128. Participants selected their preferred size and rated the acceptability of the visual experience. The preferred viewing ratio depended on the resolution and had to be at least 9.8H. The minimal angular resolution people required and which limited the up-scaling factor was 14 pixels per degree. Extreme long shots were best when depicted actors were at least 0.7° high. A second study researched the ecological validity of previous lab results by comparing them to results from the field. Image size yielded more value for users in the field than was apparent from lab results. In conclusion, current prediction models based on preferred viewing distances for TV and large displays do not predict viewing preferences on mobile devices. Our results will help to further the understanding of multimedia perception and service designers to deliver both economically viable and enjoyable experiences

Haptic-Enhanced Learning in Preclinical Operative Dentistry

Background: Virtual reality haptic simulators represent a new paradigm in dental education that may potentially impact the rate and efficiency of basic skill acquisition, as well as pedagogically influence the various aspects of students’ preclinical experience. However, the evidence to support their efficiency and inform their implementation is still limited. Objectives: This thesis set out to empirically examine how haptic VR simulator (Simodont®) can enhance the preclinical dental education experience particularly in the context of operative dentistry. We specify 4 distinct research themes to explore, namely: simulator validity (face, content and predictive), human factors in 3D stereoscopic display, motor skill acquisition, and curriculum integration. Methods: Chapter 3 explores the face and content validity of Simodont® haptic dental simulator among a group of postgraduate dental students. Chapter 4 examines the predictive utility of Simodont® in predicting subsequent preclinical and clinical performance. The results indicate the potential utility of the simulator in predicting future clinical dental performance among undergraduate students. Chapter 5 investigates the role of stereopsis in dentistry from two different perspectives via two studies. Chapter 6 explores the effect of qualitatively different types of pedagogical feedback on the training, transfer and retention of basic manual dexterity dental skills. The results indicate that the acquisition and retention of basic dental motor skills in novice trainees is best optimised through a combination of instructor and visualdisplay VR-driven feedback. A pedagogical model for integration of haptic dental simulator into the dental curriculum has been proposed in Chapter 7. Conclusion: The findings from this thesis provide new insights into the utility of the haptic virtual reality simulator in undergraduate preclinical dental education. Haptic simulators have promising potential as a pedagogical tool in undergraduate dentistry that complements the existing simulation methods. Integration of haptic VR simulators into the dental curriculum has to be informed by sound pedagogical principles and mapped into specific learning objectives