Visual impairment and the useful field of vision

Spatiotemporal Gait Differences before and after Botulinum Toxin in People with Focal Dystonia: A Pilot Study

BACKGROUND

The impact of focal dystonia on gait has attracted little attention and remains elusive. Considering the importance of both visual and head control in gait, blepharospasm and cervical dystonia should affect gait. Improvement of cervical/eyelid control following botulinum toxin (BTX) injections would translate into gait changes.

OBJECTIVES

To assess gait differences in people with focal dystonia before and after BTX treatment.

METHODS

Ten patients with blepharospasm, 10 patients with cervical dystonia, and 20 healthy age- and gender-matched controls were included. Gait was assessed before and 1-month after BTX injections using Biodex Gait Trainer™ 3. Gait velocity, cadence, step length, step asymmetry, and variability of step length were compared between patients and controls, and between the two time-points using non-parametric statistics.

RESULTS

At baseline, compared to controls, cervical dystonia patients showed reduced gait velocity, step length, and cadence. After BTX injections, while gait velocity and step length were significantly increased and step length variability reduced, gait parameters still differed between patients and controls. In blepharospasm patients, baseline gait velocity and step length were significantly smaller than in controls. After BTX injections, these gait parameters were significantly increased and variability decreased, so that patients no longer differed from controls.

CONCLUSION

Gait differences exist between patients with focal dystonia not directly affecting the lower limbs and healthy controls. These gait abnormalities were improved differently by BTX treatment according to the type of dystonia. These disparities suggest different pathophysiological mechanisms and support the need for changes in rehabilitation routines in cervical dystonia.

Usability and Accessibility of the ArtontheBrain™ Virtual Recreation Activity for Older Adults With Low Vision Due to Age-Related Macular Degeneration

Experiencing visual art can inspire, be an overall positive leisure activity, and has been linked to improved cognition, especially in older adults. Access to artwork in a museum environment can comprise a variety of barriers, including difficulties linked to its visual experience for persons that are visually impaired. The present study explored the barriers and facilitators experienced by 15 older adults (age 65 to 93) living with age-related macular degeneration when using an iPad to access ArtontheBrain™, a virtual art museum recreation experience created by members of this team. Using the Concurrent Think Aloud method, participants were asked to continuously comment on their experiences with the application while being audio/video recorded. Indeed, codes were determined by identifying frequently stated and emphasized ideas or behaviors of participants using the ArtontheBrain™ application. Transcripts underwent thematic analysis and indicated that the main access barriers were linked to control of the contrast, magnification, and the tactile interface on the tablet device. The learn and play activities as well as the text-to-speech feature were identified as facilitators for ArtontheBrain™ engagement. The present findings should also be considered in the larger context of application development, as this study provides insight pertaining to the needs of low vision individuals regarding usability and accessibility.

The association between visual attention and body movement-controlled video games, balance and mobility in older adults

Background

Body movement-controlled video games involving physical motion and visual attention may have the potential to train both abilities simultaneously. Our purpose was to determine the associations between performance in these games and visual attention, balance and mobility in a group of older adults. The long-term goal is to identify the optimal type of interactive games with regards to training potential.

Methods

Fifty healthy adults aged 65+ years participated in this cross-sectional study. Visual attention was measured with static and dynamic versions of a useful field of view (UFV) and a multiple object tracking (MOT) test. Balance was measured with a force plate in bi-pedal quiet stance test (QST) and one-legged stance (OLST). Gait variability and walking speed were assessed with the Five Meter Walk Test (5MWT). Four Microsoft™ Xbox® 360 Kinect™ interactive video games were chosen based on the apparent levels of visual attention demand.

Results

Visual attention (UFV and MOT) was significantly associated with performance in Xbox® Kinect™ games that appeared to have a high visual attention demand (p < 0.05), while there was minimal or no significant association with games with apparent low visual attention demand. Balance and mobility show correlations with visual attention, and with Xbox games.

Conclusion

The results suggest that there are relationships between visual attention, balance, mobility and Xbox® Kinect™ game performance. Since different Xbox® games were associated with different balance, mobility and visual attention scores, a variety of such games, rather than a single game, may be most effective for training for falls prevention.

Binocular Vision Disorders and Visual Attention: Associations With Balance and Mobility in Older Adults

Understanding which aspects of vision are related to falls is important. We examine the associations between tests of balance, mobility, fear of falling (FES-1) and aspects of vision in 72 adults aged 70+. Balance and mobility were examined using the One Legged Stance test (OLST), the Sit to Stand test (STST) and the 5 Meter Walking test (5MWT). Visual measures included visual acuity (VA), contrast sensitivity, stereoacuity, binocular vision (BV) measurements, Useful field of View (UFV) and Attended Field of View (AFOV). Reduced performance on the OLST and the STST was significantly correlated with abnormal BV and poorer intermediate VA. Poorer function on the 5MWT and the FES-I was also predicted by poor intermediate VA and poorer performance on the OLST, STST and the 5MWT was associated with UFV errors. The results are of high importance as many BV disorders are treatable and visual attention is trainable.

Functional visual fields: relationship of visual field areas to self-reported function

PURPOSE

The aim of this study is to relate areas of the visual field to functional difficulties to inform the development of a binocular visual field assessment that can reflect the functional consequences of visual field loss.

METHODS

Fifty-two participants with peripheral visual field loss undertook binocular assessment of visual fields using the 30-2 and 60-4 SITA Fast programs on the Humphrey Field Analyser, and mean thresholds were derived. Binocular visual acuity, contrast sensitivity and near reading performance were also determined. Self-reported overall and mobility function were assessed using the Dutch ICF Activity Inventory.

RESULTS

Greater visual field loss (0-60°) was associated with worse self-reported function both overall (R² = 0.50; p < 0.0001), and for mobility (R² = 0.64; p < 0.0001). Central (0-30°) and peripheral (30-60°) visual field areas were similarly related to mobility function (R² = 0.61, p < 0.0001 and R² = 0.63, p < 0.0001 respectively), although the peripheral (30-60°) visual field was the best predictor of mobility self-reported function in multiple regression analyses. Superior and inferior visual field areas related similarly to mobility function (R² = 0.56, p < 0.0001 and R² = 0.67, p < 0.0001 respectively). The inferior field was found to be the best predictor of mobility function in multiple regression analysis.

CONCLUSION

Mean threshold of the binocular visual field to 60° eccentricity is a good predictor of self-reported function overall, and particularly of mobility function. Both the central (0-30°) and peripheral (30-60°) mean threshold are good predictors of self-reported function, but the peripheral (30-0°) field is a slightly better predictor of mobility function, and should not be ignored when considering functional consequences of field loss. The inferior visual field is a slightly stronger predictor of perceived overall and mobility function than the superior field.

The useful field of view assessment predicts simulated commercial motor vehicle driving safety

OBJECTIVE

The Useful Field of View (UFOV) assessment, a measure of visual speed of processing, has been shown to be a predictive measure of motor vehicle collision (MVC) involvement in an older adult population, but it remains unknown whether UFOV predicts commercial motor vehicle (CMV) driving safety during secondary task engagement. The purpose of this study is to determine whether the UFOV assessment predicts simulated MVCs in long-haul CMV drivers.

METHOD

Fifty licensed CMV drivers (Mage = 39.80, SD = 8.38, 98% male, 56% Caucasian) were administered the 3-subtest version of the UFOV assessment, where lower scores measured in milliseconds indicated better performance. CMV drivers completed 4 simulated drives, each spanning approximately a 22.50-mile distance. Four secondary tasks were presented to participants in a counterbalanced order during the drives: (a) no secondary task, (b) cell phone conversation, (c) text messaging interaction, and (d) e-mailing interaction with an on-board dispatch device.

RESULTS

The selective attention subtest significantly predicted simulated MVCs regardless of secondary task. Each 20 ms slower on subtest 3 was associated with a 25% increase in the risk of an MVC in the simulated drive. The e-mail interaction secondary task significantly predicted simulated MVCs with a 4.14 times greater risk of an MVC compared to the no secondary task condition. Subtest 3, a measure of visual speed of processing, significantly predicted MVCs in the email interaction task. Each 20 ms slower on subtest 3 was associated with a 25% increase in the risk of an MVC during the email interaction task.

CONCLUSIONS

The UFOV subtest 3 may be a promising measure to identify CMV drivers who may be at risk for MVCs or in need of cognitive training aimed at improving speed of processing. Subtest 3 may also identify CMV drivers who are particularly at risk when engaged in secondary tasks while driving.

Cognitive speed of processing training in older adults with visual impairments

PURPOSE

To examine whether older adults with vision impairment differentially benefit from cognitive speed of processing training (SPT) relative to healthy older adults.

METHODS

Secondary data analyses were conducted from a randomised trial on the effects of SPT among older adults. The effects of vision impairment as indicated by (1) near visual acuity, (2) contrast sensitivity, (3) self-reported cataracts and (4) self-reported other eye conditions (e.g., glaucoma, macular degeneration, diabetic retinopathy, optic neuritis, and retinopathy) among participants randomised to either SPT or a social- and computer-contact control group was assessed. The primary outcome was Useful Field of View Test (UFOV) performance.

RESULTS

Mixed repeated-measures ancovas demonstrated that those randomized to SPT experienced greater baseline to post-test improvements in UFOV performance relative to controls (p's < 0.001), regardless of impairments in near visual acuity, contrast sensitivity or presence of cataracts. Those with other eye conditions significantly benefitted from training (p = 0.044), but to a lesser degree than those without such conditions. Covariates included age and baseline measures of balance and depressive symptoms, which were significantly correlated with baseline UFOV performance.

CONCLUSIONS

Among a community-based sample of older adults with and without visual impairment and eye disease, the SPT intervention was effective in enhancing participants' UFOV performance. The analyses presented here indicate the potential for SPT to enhance UFOV performance among a community-based sample of older adults with visual impairment and potentially for some with self-reported eye disease; further research to explore this area is warranted, particularly to determine the effects of eye diseases on SPT benefits.

Predicting Motor Vehicle Collisions in a Driving Simulator in Young Adults Using the Useful Field of View Assessment

OBJECTIVE

Being involved in motor vehicle collisions is the leading cause of death in 1- to 34-year-olds, and risk is particularly high in young adults. The Useful Field of View (UFOV) task, a cognitive measure of processing speed, divided attention, and selective attention, has been shown to be predictive of motor vehicle collisions in older adults, but its use as a predictor of driving performance in a young adult population has not been investigated. The present study examined whether UFOV was a predictive measure of motor vehicle collisions in a driving simulator in a young adult population.

METHOD

The 3-subtest version of UFOV (lower scores measured in milliseconds indicate better performance) was administered to 60 college students. Participants also completed an 11-mile simulated drive to provide driving performance metrics.

RESULTS

Findings suggested that subtests 1 and 2 suffered from a ceiling effect. UFOV subtest 3 significantly predicted collisions in the simulated drive. Each 30 ms slower on the subtest was associated with nearly a 10% increase in the risk of a simulated collision. Post hoc analyses revealed a small partially mediating effect of subtest 3 on the relationship between driving experience and collisions.

CONCLUSION

The selective attention component of UFOV subtest 3 may be a predictive measure of crash involvement in a young adult population. Improvements in selective attention may be the underlying mechanism in how driving experience improves driving performance.

Effect of age and pop out distracter on attended field of view

PURPOSE

To investigate the functional field of view (FFOV) of younger and older individuals using the attended field of view (AFOV), a method which allows for eye and head movement. The impact of a pop out distracter and a dual task on the FFOV measure was also investigated.

METHODS

Nine young adult (25±6 years) and 9 older participants (72±4 years) took part in the experiment. The AFOV test involved the binocular detection and localization of a white target (Landolt-C) in a field of 24 white rings (distracters). The further AFOV tests were modified to include the presence of a pop out distracter, a dual task condition, and a combination of the two.

RESULTS

Older observers had lower viewing efficiency (log [1/presentation time]) in all conditions (pooled mean across conditions: older: 0.05±0.02; younger: 0.48±0.04) than the younger group. The addition of dual or a pop out distracter did not affect the older group (mean difference ∼104±150ms and ∼124±122ms respectively) but the additional pop out distracter reduced the efficiency of the younger group for targets near fixation (mean difference ∼68±35ms).

CONCLUSION

Better viewing efficiency was observed in younger individuals compared to older individuals. Difficulty in disregarding irrelevant stimuli and thereby resorting to inefficient search strategy is proposed as the reason for the differences. The finding that both older and younger individuals are not affected significantly by the presence of the irrelevant pop out distracter has implications in situations such as driving or hazard avoidance. In such scenarios, search performance is likely not impaired beyond what is found with distracters (visual clutter) in the environment.

Useful field of view test

The useful field of view test was developed to reflect the visual difficulties that older adults experience with everyday tasks. Importantly, the useful field of view test (UFOV) is one of the most extensively researched and promising predictor tests for a range of driving outcomes measures, including driving ability and crash risk as well as other everyday tasks. Currently available commercial versions of the test can be administered using personal computers; these measure the speed of visual processing for rapid detection and localization of targets under conditions of divided visual attention and in the presence and absence of visual clutter. The test is believed to assess higher-order cognitive abilities, but performance also relies on visual sensory function because in order for targets to be attended to, they must be visible. The format of the UFOV has been modified over the years; the original version estimated the spatial extent of useful field of view, while the latest version measures visual processing speed. While deficits in the useful field of view are associated with functional impairments in everyday activities in older adults, there is also emerging evidence from several research groups that improvements in visual processing speed can be achieved through training. These improvements have been shown to reduce crash risk, and can have a positive impact on health and functional well-being, with the potential to increase the mobility and hence the independence of older adults.

The decline in attentional visual fields over time among older participants in the Salisbury Eye Evaluation Driving Study

PURPOSE

The loss of attentional visual field (AVF) has been linked to poor mobility and car crashes. We investigated the risk factors associated with a decrease in AVF over time among participants in the Salisbury Eye Evaluation Driving Study (SEEDS).

METHODS

In a longitudinal cohort of 968 individuals ages 67 to 87, demographic, medical, visual, and cognitive factors were obtained at baseline (2005-2006) and follow-up (2007-2008) using structured medical questionnaires and onsite examinations. Using the standard deviation for the difference in AVF over 2 years of 4.3°, two subgroups were created: Those who lost 5° or more in two years and those who had no loss (i.e., loss of 5° or less, or no loss). Age-adjusted and multivariate odds ratios (OR) with 95% confidence intervals (95% CI) for each explanatory factor were determined using logistic regression.

RESULTS

The overall change in AVF was -0.34° (SD = 4.32), which was a significant decline from baseline. of the population, 14% lost 5° or more of AVF. The following determinants were associated with a minimum loss of 5° over 2 years: female sex (OR = 1.59, P = 0.03), history of stroke (OR = 1.90, P = 0.03), depression (OR = 1.07, P = 0.02), a lower baseline Trails A and B scores (OR = 1.09, P = 0.003 and OR = 1.02, P = 0.02, respectively), and lower baseline visual acuity (OR = 1.21, P = 0.03). In addition, decline was related to a lower baseline measure of auditory attention (OR = 1.14, P = 0.007) and lower baseline visual fields in the central 20° (OR = 1.24, P = 0.01).

CONCLUSIONS

Loss in AVF over time is related independently to decrements in cognition and vision. The higher odds of loss in female subjects, independent of these factors, deserves further research.

Visual processing speed

Older adults commonly report difficulties in visual tasks of everyday living that involve visual clutter, secondary task demands, and time sensitive responses. These difficulties often cannot be attributed to visual sensory impairment. Techniques for measuring visual processing speed under divided attention conditions and among visual distractors have been developed and have established construct validity in that those older adults performing poorly in these tests are more likely to exhibit daily visual task performance problems. Research suggests that computer-based training exercises can increase visual processing speed in older adults and that these gains transfer to enhancement of health and functioning and a slowing in functional and health decline as people grow older.

Differential impact of partial cortical blindness on gaze strategies when sitting and walking - an immersive virtual reality study

The present experiments aimed to characterize the visual performance of subjects with long-standing, unilateral cortical blindness when walking in a naturalistic, virtual environment. Under static, seated testing conditions, cortically blind subjects are known to exhibit compensatory eye movement strategies. However, they still complain of significant impairment in visual detection during navigation. To assess whether this is due to a change in compensatory eye movement strategy between sitting and walking, we measured eye and head movements in subjects asked to detect peripherally-presented, moving basketballs. When seated, cortically blind subjects detected ∼80% of balls, while controls detected almost all balls. Seated blind subjects did not make larger head movements than controls, but they consistently biased their fixation distribution towards their blind hemifield. When walking, head movements were similar in the two groups, but the fixation bias decreased to the point that fixation distribution in cortically blind subjects became similar to that in controls - with one major exception: at the time of basketball appearance, walking controls looked primarily at the far ground, in upper quadrants of the virtual field of view; cortically blind subjects looked significantly more at the near ground, in lower quadrants of the virtual field. Cortically blind subjects detected only 58% of the balls when walking while controls detected ∼90%. Thus, the adaptive gaze strategies adopted by cortically blind individuals as a compensation for their visual loss are strongest and most effective when seated and stationary. Walking significantly alters these gaze strategies in a way that seems to favor walking performance, but impairs peripheral target detection. It is possible that this impairment underlies the experienced difficulty of those with cortical blindness when navigating in real life.

Visual function, visual attention, and mobility performance in low vision

PURPOSE

The aim of this study was to determine if useful field of view (UFV) measures help to predict aspects of orientation and mobility in people with visual impairment. The UFV is a composite measure of visual attention, ability to detect objects in the presence of clutter and basic visual functions such as visual field loss and contrast sensitivity.

METHODS

Thirty-five participants aged 20 to 80 years with low vision due to a variety of visual disorders took part. Mobility around a partly indoor and exterior real-life mobility course was measured, together with UFV and clinical measures of contrast sensitivity (CS), visual fields, and visual acuity. Two series of models were considered; series 1 using the UFV scores as measured and series 2 using the UFV scores corrected for visual field loss (only counting errors in areas of intact visual field).

RESULTS

UFV was found to be an important predictor of some aspects of mobility performance. Mobility errors were best predicted by uncorrected UFV (R = 0.38), although CS was also a good predictor. Walking speed and preferred walking speed (PWS) were best predicted by uncorrected UFV and age (R = 0.575 and 0.573, respectively). The visual detection distance and visual identification distances were best predicted by clinical vision measures, such as contrast sensitivity, visual fields, and central vision function. The percent PWS was not predicted by any of the measures we used. None of these models was improved by the addition of the corrected UFV scores.

CONCLUSIONS

These results indicate that attention and the presence of distractors, as well as visual function and age, are important factors in orientation and mobility performance, in particular mobility errors, walking speed and PWS.