Mobility Enhancement & Vision Rehabilitation

Mobility Enhancement & Vision Rehabilitation Publications

Xu J, Emmermann B, Bowers AR. Auditory Reminder Cues to Promote Proactive Scanning on Approach to Intersections in Drivers With Homonymous Hemianopia: Driving With Hemianopia, IX. JAMA Ophthalmol 2022;140(1):75-78.Abstract
Importance: Individuals with homonymous hemianopia (HH) are permitted to drive in some jurisdictions. They could compensate for their hemifield vision loss by scanning toward the blind side. However, some drivers with HH do not scan adequately well to the blind side when approaching an intersection, resulting in delayed responses to hazards. Objective: To evaluate whether auditory reminder cues promoted proactive scanning on approach to intersections. Design, Setting, and Participants: This cross-sectional, single-visit driving simulator study was conducted from October 2018 to May 2019 at a vision rehabilitation research laboratory. A volunteer sample of individuals with HH without visual neglect are included in this analysis. This post hoc analysis was completed in July and August 2020. Main Outcomes and Measures: Participants completed drives with and without scanning reminder cues (a single tone from a speaker on the blind side). Scanning was quantified by the percentage of intersections at which an early large scan was made (a scan with a head movement of at least 20° made before 30 m from the intersection). Responses to motorcycle hazards at intersections were quantified by the time to the first fixation and the time to the horn-press response. Results: Sixteen individuals were recruited and completed the study. Two were subsequently excluded from analyses. Thus, data from 14 participants (median [IQR] age, 54 [36-66] years; 13 men [93%]) were included. Stroke was the primary cause of the HH (10 participants [71%]). Six (43%) had right-sided HH. Participants were more likely to make an early large scan to the blind side in drives with vs without cues (65% vs 45%; difference, 20% [95% CI, 5%-37%]; P < .001). When participants made an early large scan to the blind side, they were faster to make their first fixation on blind-side motorcycles (mean [SD], 1.77 [1.34] vs 3.88 [1.17] seconds; difference, -2.11 [95% CI, -2.46 to -1.75] seconds; P < .001) and faster to press the horn (mean [SD], 2.54 [1.19] vs 4.54 [1.37] seconds; difference, -2.00 [95% CI, -2.38 to -1.62] seconds; P < .001) than when they did not make an early scan. Conclusions and Relevance: This post hoc analysis suggests that auditory reminder cues may promote proactive scanning, which may be associated with faster responses to hazards. This hypothesis should be considered in future prospective studies.
Jung J-H, Kurukuti NM, Peli E. Photographic Depiction of the Field of View with Spectacles-mounted Low Vision Aids. Optom Vis Sci 2021;98(10):1210-1226.Abstract
SIGNIFICANCE: Photographic depiction helps to illustrate the primary and secondary field of view effects of low vision devices along with their utility to clinicians, patients, and caretakers. This technique may also be helpful for designers and researchers in improving the design and fitting of low vision devices. PURPOSE: The field of view through spectacles-mounted low vision devices has typically been evaluated using perimetry. However, the perimetric field diagram is different from the retinal image and often fails to represent the important aspects of the field of view and visual parameters. We developed a photographic depiction method to record and veridically show the field of view effects of these devices. METHODS: We used a 3D-printed holder to place spectacles-mounted devices at the same distance from the empirically determined reference point of the field of view in a camera lens (f = 16 mm) as they would be from an eye, when in use. The field of view effects of a bioptic telescope, a minifier (reverse telescope), and peripheral prisms were captured using a conventional camera, representing retinal images. The human eye pupil size (adjusting the F number: f/2.8 to f/8 and f/22 in the camera lens) and fitting parameters (pantoscopic tilt and back vertex distance) varied. RESULTS: Real-world indoor and outdoor walking and driving scenarios were depicted as retinal images illustrating the field of view through low vision devices, distinguishing optical and obscuration scotomas, and demonstrating secondary effects (spatial distortions, viewpoint changes, diplopia, spurious reflection, and multiplexing effects) not illustrated by perimetric field diagrams. CONCLUSIONS: Photographic depiction illustrates the primary and secondary field of view effects of the low vision devices. These images highlight the benefit and possible trade-offs of the low vision devices and may be beneficial in education and training.
Wiegand I, Wolfe JM. Target value and prevalence influence visual foraging in younger and older age. Vision Res 2021;186:87-102.Abstract
The prevalence and reward-value of targets have an influence on visual search. The strength of the effect of an item's reward-value on attentional selection varies substantially between individuals and is potentially sensitive to aging. We investigated individual and age differences in a hybrid foraging task, in which the prevalence and value of multiple target types was varied. Using optimal foraging theory measures, foraging was more efficient overall in younger than older observers. However, the influence of prevalence and value on target selections was similar across age groups, suggesting that the underlying cognitive mechanisms are preserved in older age. When prevalence was varied but target value was balanced, younger and older observers preferably selected the most frequent target type and were biased to select another instance of the previously selected target type. When value was varied, younger and older observers showed a tendency to select high-value targets, but preferences were more diverse between individuals. When value and prevalence were inversely related, some observers showed particularly strong preferences for high-valued target types, while others showed a preference for high-prevalent, albeit low-value, target types. In younger adults, individual differences in the selection choices correlated with a personality index, suggesting that avoiding selections of low-value targets may be related to reward-seeking behaviour.
Muralidharan S, Ichhpujani P, Bhartiya S, Singh RB. Eye-tunes: role of music in ophthalmology and vision sciences. Ther Adv Ophthalmol 2021;13:25158414211040890.Abstract
Although the healing effect of music has been recognized since time immemorial, there has been a renewed interest in its use in modern medicine. This can be attributed to the increasing focus on holistic healing and on the subjective and objective aspects of well-being. In ophthalmology, this has ranged from using music for patients undergoing diagnostic procedures and surgery, as well as for doctors and the operation theatre staff during surgical procedures. Music has proven to be a potent nonpharmacological sedative and anxiolytic, allaying both the pain and stress of surgery. This review aims to explore the available evidence about the role of music as an adjunct for diagnostic and surgical procedures in current ophthalmic practices.
Avraham D, Jung J-H, Yitzhaky Y, Peli E. Retinal prosthetic vision simulation: temporal aspects. J Neural Eng 2021;18(4)Abstract
Objective. The perception of individuals fitted with retinal prostheses is not fully understood, although several retinal implants have been tested and commercialized. Realistic simulations of perception with retinal implants would be useful for future development and evaluation of such systems.Approach.We implemented a retinal prosthetic vision simulation, including temporal features, which have not been previously simulated. In particular, the simulation included temporal aspects such as persistence and perceptual fading of phosphenes and the electrode activation rate.Main results.The simulated phosphene persistence showed an effective reduction in flickering at low electrode activation rates. Although persistence has a positive effect on static scenes, it smears dynamic scenes. Perceptual fading following continuous stimulation affects prosthetic vision of both static and dynamic scenes by making them disappear completely or partially. However, we showed that perceptual fading of a static stimulus might be countered by head-scanning motions, which together with the persistence revealed the contours of the faded object. We also showed that changing the image polarity may improve simulated prosthetic vision in the presence of persistence and perceptual fading.Significance.Temporal aspects have important roles in prosthetic vision, as illustrated by the simulations. Considering these aspects may improve the future design, the training with, and evaluation of retinal prostheses.
Pundlik S, Baliutaviciute V, Moharrer M, Bowers AR, Luo G. Home-Use Evaluation of a Wearable Collision Warning Device for Individuals With Severe Vision Impairments: A Randomized Clinical Trial. JAMA Ophthalmol 2021;139(9):998-1005.Abstract
Importance: There is scant rigorous evidence about the real-world mobility benefit of electronic mobility aids. Objective: To evaluate the effect of a collision warning device on the number of contacts experienced by blind and visually impaired people in their daily mobility. Design, Setting, and Participants: In this double-masked randomized clinical trial, participants used a collision warning device during their daily mobility over a period of 4 weeks. A volunteer sample of 31 independently mobile individuals with severe visual impairments, including total blindness and peripheral visual field restrictions, who used a long cane or guide dog as their habitual mobility aid completed the study. The study was conducted from January 2018 to December 2019. Interventions: The device automatically detected collision hazards using a chest-mounted video camera. It randomly switched between 2 modes: active mode (intervention condition), where it provided alerts for detected collision threats via 2 vibrotactile wristbands, and silent mode (control condition), where the device still detected collisions but did not provide any warnings to the user. Scene videos along with the collision warning information were recorded by the device. Potential collisions detected by the device were reviewed and scored, including contacts with the hazards, by 2 independent reviewers. Participants and reviewers were masked to the device operation mode. Main Outcomes and Measures: Rate of contacts per 100 hazards per hour, compared between the 2 device modes within each participant. Modified intention-to-treat analysis was used. Results: Of the 31 included participants, 18 (58%) were male, and the median (range) age was 61 (25-73) years. A total of 19 participants (61%) had a visual acuity (VA) of light perception or worse, and 28 (90%) reported a long cane as their habitual mobility aid. The median (interquartile range) number of contacts was lower in the active mode compared with silent mode (9.3 [6.6-14.9] vs 13.8 [6.9-24.3]; difference, 4.5; 95% CI, 1.5-10.7; P < .001). Controlling for demographic characteristics, presence of VA better than light perception, and fall history, the rate of contacts significantly reduced in the active mode compared with the silent mode (β = 0.63; 95% CI, 0.54-0.73; P < .001). Conclusions and Relevance: In this study involving 31 visually impaired participants, the collision warnings were associated with a reduced rate of contacts with obstacles in daily mobility, indicating the potential of the device to augment habitual mobility aids. Trial Registration: ClinicalTrials.gov Identifier: NCT03057496.
Costela FM, Reeves SM, Woods RL. The Effect of Zoom Magnification and Large Display on Video Comprehension in Individuals With Central Vision Loss. Transl Vis Sci Technol 2021;10(8):30.Abstract
Purpose: A larger display at the same viewing distance provides relative-size magnification for individuals with central vision loss (CVL). However, the resulting large visible area of the display is expected to result in more head rotation, which may cause discomfort. We created a zoom magnification technique that placed the center of interest (COI) in the center of the display to reduce the need for head rotation. Methods: In a 2 × 2 within-subject study design, 23 participants with CVL viewed video clips from 1.5 m (4.9 feet) shown with or without zoom magnification, and with a large (208 cm/82" diagonal, 69°) or a typical (84 cm/33", 31°) screen. Head position was tracked and a custom questionnaire was used to measure discomfort. Results: Video comprehension was better with the large screen (P < 0.001) and slightly worse with zoom magnification (P = 0.03). Oddly, head movements did not vary with screen size (P = 0.63), yet were greater with zoom magnification (P = 0.001). This finding was unexpected, because the COI remains in the center with zoom magnification, but moves widely with a large screen and no magnification. Conclusions: This initial attempt to implement the zoom magnification method had flaws that may have decreased its effectiveness. In the future, we propose alternative implementations for zoom magnification, such as variable magnification. Translational Relevance: We present the first explicit demonstration that relative-size magnification improves the video comprehension of people with CVL when viewing video.
Saeedi O, Boland MV, D'Acunto L, Swamy R, Hegde V, Gupta S, Venjara A, Tsai J, Myers JS, Wellik SR, DeMoraes G, Pasquale LR, Shen LQ, Li Y, Elze T. Development and Comparison of Machine Learning Algorithms to Determine Visual Field Progression. Transl Vis Sci Technol 2021;10(7):27.Abstract
Purpose: To develop and test machine learning classifiers (MLCs) for determining visual field progression. Methods: In total, 90,713 visual fields from 13,156 eyes were included. Six different progression algorithms (linear regression of mean deviation, linear regression of the visual field index, Advanced Glaucoma Intervention Study algorithm, Collaborative Initial Glaucoma Treatment Study algorithm, pointwise linear regression [PLR], and permutation of PLR) were applied to classify each eye as progressing or stable. Six MLCs were applied (logistic regression, random forest, extreme gradient boosting, support vector classifier, convolutional neural network, fully connected neural network) using a training and testing set. For MLC input, visual fields for a given eye were divided into the first and second half and each location averaged over time within each half. Each algorithm was tested for accuracy, sensitivity, positive predictive value, and class bias with a subset of visual fields labeled by a panel of three experts from 161 eyes. Results: MLCs had similar performance metrics as some of the conventional algorithms and ranged from 87% to 91% accurate with sensitivity ranging from 0.83 to 0.88 and specificity from 0.92 to 0.96. All conventional algorithms showed significant class bias, meaning each individual algorithm was more likely to grade uncertain cases as either progressing or stable (P ≤ 0.01). Conversely, all MLCs were balanced, meaning they were equally likely to grade uncertain cases as either progressing or stable (P ≥ 0.08). Conclusions: MLCs showed a moderate to high level of accuracy, sensitivity, and specificity and were more balanced than conventional algorithms. Translational Relevance: MLCs may help to determine visual field progression.
Wiegand I, Westenberg E, Wolfe JM. Order, please! Explicit sequence learning in hybrid search in younger and older age. Mem Cognit 2021;49(6):1220-1235.Abstract
Sequence learning effects in simple perceptual and motor tasks are largely unaffected by normal aging. However, less is known about sequence learning in more complex cognitive tasks that involve attention and memory processes and how this changes with age. In this study, we examined whether incidental and intentional sequence learning would facilitate hybrid visual and memory search in younger and older adults. Observers performed a hybrid search task, in which they memorized four or 16 target objects and searched for any of those target objects in displays with four or 16 objects. The memorized targets appeared either in a repeating sequential order or in random order. In the first experiment, observers were not told about the sequence before the experiment. Only a subset of younger adults and none of the older adults incidentally learned the sequence. The "learners" acquired explicit knowledge about the sequence and searched faster in the sequence compared to random condition. In the second experiment, observers were told about the sequence before the search task. Both younger and older adults searched faster in sequence blocks than random blocks. Older adults, however, showed this sequence-learning effect only in blocks with smaller target sets. Our findings indicate that explicit sequence knowledge can facilitate hybrid search, as it allows observers to predict the next target and restrict their visual and memory search. In older age, the sequence-learning effect is constrained by load, presumably due to age-related decline in executive functions.
Costela FM, Reeves SM, Woods RL. An implementation of Bubble Magnification did not improve the video comprehension of individuals with central vision loss. Ophthalmic Physiol Opt 2021;41(4):842-852.Abstract
PURPOSE: People with central vision loss (CVL) watch television, videos and movies, but often report difficulty and have reduced video comprehension. An approach to assist viewing videos is electronic magnification of the video itself, such as Bubble Magnification. METHODS: We created a Bubble Magnification technique that displayed a magnified segment around the centre of interest (COI) as determined by the gaze of participants with normal vision. The 15 participants with CVL viewed video clips shown with 2× and 3× Bubble Magnification, and unedited. We measured video comprehension and gaze coherence. RESULTS: Video comprehension was significantly worse with both 2× (p = 0.01) and 3× Bubble Magnification (p < 0.001) than the unedited video. There was no difference in gaze coherence across conditions (p ≥ 0.58). This was unexpected because we expected a benefit in both video comprehension and gaze coherence. This initial attempt to implement the Bubble Magnification method had flaws that probably reduced its effectiveness. CONCLUSIONS: In the future, we propose alternative implementations of Bubble Magnification, such as variable magnification and bubble size. This study is a first step in the development of an intelligent-magnification approach to providing a vision rehabilitation aid to assist people with CVL.
Wolfe JM. Guided Search 6.0: An updated model of visual search. Psychon Bull Rev 2021;28(4):1060-1092.Abstract
This paper describes Guided Search 6.0 (GS6), a revised model of visual search. When we encounter a scene, we can see something everywhere. However, we cannot recognize more than a few items at a time. Attention is used to select items so that their features can be "bound" into recognizable objects. Attention is "guided" so that items can be processed in an intelligent order. In GS6, this guidance comes from five sources of preattentive information: (1) top-down and (2) bottom-up feature guidance, (3) prior history (e.g., priming), (4) reward, and (5) scene syntax and semantics. These sources are combined into a spatial "priority map," a dynamic attentional landscape that evolves over the course of search. Selective attention is guided to the most active location in the priority map approximately 20 times per second. Guidance will not be uniform across the visual field. It will favor items near the point of fixation. Three types of functional visual field (FVFs) describe the nature of these foveal biases. There is a resolution FVF, an FVF governing exploratory eye movements, and an FVF governing covert deployments of attention. To be identified as targets or rejected as distractors, items must be compared to target templates held in memory. The binding and recognition of an attended object is modeled as a diffusion process taking > 150 ms/item. Since selection occurs more frequently than that, it follows that multiple items are undergoing recognition at the same time, though asynchronously, making GS6 a hybrid of serial and parallel processes. In GS6, if a target is not found, search terminates when an accumulating quitting signal reaches a threshold. Setting of that threshold is adaptive, allowing feedback about performance to shape subsequent searches. Simulation shows that the combination of asynchronous diffusion and a quitting signal can produce the basic patterns of response time and error data from a range of search experiments.
Swan G, Savage SW, Zhang L, Bowers AR. Driving With Hemianopia VII: Predicting Hazard Detection With Gaze and Head Scan Magnitude. Transl Vis Sci Technol 2021;10(1):20.Abstract
Purpose: One rehabilitation strategy taught to individuals with hemianopic field loss (HFL) is to make a large blind side scan to quickly identify hazards. However, it is not clear what the minimum threshold is for how large the scan should be. Using driving simulation, we evaluated thresholds (criteria) for gaze and head scan magnitudes that best predict detection safety. Methods: Seventeen participants with complete HFL and 15 with normal vision (NV) drove through 4 routes in a virtual city while their eyes and head were tracked. Participants pressed the horn as soon as they detected a motorcycle (10 per drive) that appeared 54 degrees eccentricity on cross-streets and approached toward the driver. Results: Those with HFL detected fewer motorcycles than those with NV and had worse detection on the blind side than the seeing side. On the blind side, both safe detections and early detections (detections before the hazard entered the intersection) could be predicted with both gaze (safe 18.5 degrees and early 33.8 degrees) and head (safe 19.3 degrees and early 27 degrees) scans. However, on the seeing side, only early detections could be classified with gaze (25.3 degrees) and head (9.0 degrees). Conclusions: Both head and gaze scan magnitude were significant predictors of detection on the blind side, but less predictive on the seeing side, which was likely driven by the ability to use peripheral vision. Interestingly, head scans were as predictive as gaze scans. Translational Relevance: The minimum scan magnitude could be a useful criterion for scanning training or for developing assistive technologies to improve scanning.
Bennett CR, Bex PJ, Merabet LB. Assessing visual search performance using a novel dynamic naturalistic scene. J Vis 2021;21(1):5.Abstract
Daily activities require the constant searching and tracking of visual targets in dynamic and complex scenes. Classic work assessing visual search performance has been dominated by the use of simple geometric shapes, patterns, and static backgrounds. Recently, there has been a shift toward investigating visual search in more naturalistic dynamic scenes using virtual reality (VR)-based paradigms. In this direction, we have developed a first-person perspective VR environment combined with eye tracking for the capture of a variety of objective measures. Participants were instructed to search for a preselected human target walking in a crowded hallway setting. Performance was quantified based on saccade and smooth pursuit ocular motor behavior. To assess the effect of task difficulty, we manipulated factors of the visual scene, including crowd density (i.e., number of surrounding distractors) and the presence of environmental clutter. In general, results showed a pattern of worsening performance with increasing crowd density. In contrast, the presence of visual clutter had no effect. These results demonstrate how visual search performance can be investigated using VR-based naturalistic dynamic scenes and with high behavioral relevance. This engaging platform may also have utility in assessing visual search in a variety of clinical populations of interest.

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