How does the extent of central visual field loss affect adaptive gait?

Simulation of visual impairment in persons with normal vision for scientific research

Simulation of visual impairment in healthy eyes has multiple applications in students' training, research and product development. However, due to the absence of an existing standard protocol, the method of simulation was left to the discretion of the researcher. This review aimed to outline the various methods of simulating visual impairment and categorising them. A scoping review of the relevant publications was conducted. Of the 1593 articles originally retrieved from the databases, 103 were included in the review. The characteristics of the participants, the method for simulation of the visual impairment in persons with normal vision and the level or type of visual impairment that was simulated were extracted from the papers. None of the methods of simulation can be judged as being superior to the others. However, electronic displays produced the most consistent form of visual impairment simulation.

Effects of Simulated Visual Impairment Conditions on Movement and Anxiety during Gap Crossing

This study investigated the effects of visual conditions associated with progressive eye disease on movement patterns and anxiety levels during gap-crossing tasks. Notably, 15 healthy young adults performed crossover platforms with a 10 cm gap at three different heights, namely equal (0 cm), raised (+15 cm), and lowered (-15 cm) levels, under four vision conditions, namely normal or corrected eyesight, 10° tunnel vision, 5° tunnel vision, and 5° tunnel vision with 0.04 occlusion. Leg movements during gap crossing were analyzed using three-dimensional motion analysis. The results highlighted a distinct motion pattern in the trajectories of participants' legs under the different visual conditions. Specifically, at the point where the gap-crossing movement began (D1), the normal or corrected eyesight conditions resulted in further separation between the steps compared with the other visual conditions. The highest point of the foot during movement (D2) did not differ between the visual conditions, except for the 0 cm step. Furthermore, anxiety levels, as quantified by the State-Trait Anxiety Inventory (STAI-S) questionnaire, were exacerbated under conditions of restricted visual information. In conclusion, visual impairments associated with progressive ocular diseases may perturb complex motor movement patterns, including those involved in gap-crossing tasks, with heightened anxiety potentially amplifying these disturbances.

Effects of Mobile Phone Use on Gait and Balance Control in Young Adults: A Hip-Ankle Strategy

BACKGROUND

This study aimed to derive the effects of walking while using a mobile phone on balance perturbation and joint movement among young adults.

METHODS

Sixteen healthy college students with no history of brain injury were tested. The participants were asked to walk under four different conditions: (1) walking, (2) browsing, (3) dialing, and (4) texting. Indicators related to balance control and lower limb kinematic/kinetic parameters were analyzed using the continuous relative phase and statistical nonparametric mapping methods.

RESULTS

Walking while using a mobile phone slowed participants' gait speed and reduced the cadence, stride length, and step length. The posterior tilt angle (0-14%, 57-99%), torque of the hip flexion (0-15%, 30-35%, 75-100%), and angle of the hip flexion (0-28%, 44-100%) decreased significantly. The activation of biceps femoris and gastrocnemius, hip stiffness, and ankle stiffness increased significantly. This impact on gait significantly differed among three dual tasks: texting > browsing > dialing.

CONCLUSION

Che overlap of walking and mobile phone use affects the gait significantly. The "hip-ankle strategy" may result in a "smooth" but slower gait, while this strategy was deliberate and tense. In addition, this adjustment also increases the stiffness of the hip and ankle, increasing the risk of fatigue. Findings regarding this effect may prove that even for young healthy adults, walking with mobile phone use induces measurable adjustment of the motor pattern. These results suggest the importance of simplifying the control of the movement.

Topical Review: Impact of Central Vision Loss on Navigation and Obstacle Avoidance while Walking

SIGNIFICANCE

Individuals with central vision loss are at higher risk of injury when walking and thus may limit trips outside the home. Understanding the mobility challenges associated with central vision loss (CVL) can lead to more effective interventions.A systematic literature review focusing on mobility in CVL was conducted. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method, 2424 articles were identified in 4 databases (PsycINFO, APA PsycArticles, PubMed, and Web of Science). To be included within this review, the study methodology needed to be related to the three components of walking: (1) navigation, defined as the ability to reach a target destination; (2) obstacle avoidance, defined as the ability to avoid collisions with obstacles located at various heights and directions; and (3) street crossing, defined as the ability to both navigate a path and avoid collisions in a traffic environment. The methodology also needed to be empirical. Case studies, unstructured observational studies, studies based on self-report, research proposals, and existing systematic reviews were excluded. Titles, abstracts, and full text of identified articles were screened, yielding 26 articles included in the review. Results showed that, in many tasks, individuals with CVL can accomplish a level of performance comparable with individuals with normal vision. Differences between normal and impaired vision were due to either age or how the groups completed the task. For example, individuals with CVL could cross a street successfully but did so less safely (i.e., smaller safety margins) than individuals with normal vision. To identify new interventions for CVL, future research should focus on the differences in the mechanisms underlying mobility between individuals with normal and impaired vision rather than solely on performance differences.

Association between the Horizontal Gaze Ability and Physical Characteristics of Patients with Dropped Head Syndrome

Background and Objectives: Patients with dropped head syndrome exhibit weakness of the cervical paraspinal muscles. However, the relationship between horizontal gaze disorder and physical function remains unclear. This study aimed to examine and clarify this relationship. Materials and Methods: Ninety-six patients with dropped head syndrome were included. We measured the McGregor’s Slope and investigated physical characteristics, including cervical muscle strength, back muscle strength, and walking ability. Factor analysis was used to classify the characteristics of physical function, and a linear multiple regression analysis was used to evaluate independent variables explaining the variance in the McGregor’s Slope. The physical functions of DHS patients were classified into three categories by factor analysis: limb and trunk muscle strength, walking ability, and neck muscle strength. Results: The average value of the McGregor’s Slope was 22.2 ± 24.0 degrees. As a result of multiple regression analysis, walking speed (β = −0.46) and apex (β = −0.30) were extracted as significant factors influencing the McGregor’s Slope. Conclusions: Horizontal gaze disorders are not associated with cervical muscle strength but with the walking ability and the alignment type of dropped head syndrome.

A low-cost 2-D video system can accurately and reliably assess adaptive gait kinematics in healthy and low vision subjects

3-D gait analysis is the gold standard but many healthcare clinics and research institutes would benefit from a system that is inexpensive and simple but just as accurate. The present study examines whether a low-cost 2-D motion capture system can accurately and reliably assess adaptive gait kinematics in subjects with central vision loss, older controls, and younger controls. Subjects were requested to walk up and step over a 10 cm high obstacle that was positioned in the middle of a 4.5 m walkway. Four trials were simultaneously recorded with the Vicon motion capture system (3-D system) and a video camera that was positioned perpendicular to the obstacle (2-D system). The kinematic parameters (crossing height, crossing velocity, foot placement, single support time) were calculated offline. Strong Pearson’s correlations were found between the two systems for all parameters (average r = 0.944, all p < 0.001). Bland-Altman analysis showed that the agreement between the two systems was good in all three groups after correcting for systematic biases related to the 2-D marker positions. The test-retest reliability for both systems was high (average ICC = 0.959). These results show that a low-cost 2-D video system can reliably and accurately assess adaptive gait kinematics in healthy and low vision subjects.

Cognitive load of walking in people who are blind: Subjective and objective measures for assessment

BACKGROUND

Although walking without vision seems to carry a high cognitive cost, few studies have measured the cognitive load involved in this activity in blind people. The aim of this study was to assess the cognitive load of walking in blind people, using gait analysis, a dual task paradigm and a subjective assessment of cognitive load.

METHODS

In a quantitative quasi-experimental design, 25 blind adults walked 40 meters. In one trial, participants walked normally (control condition). In another, they walked while performing an auditory simple reaction time task, and in the third trial they walked, performed the simple reaction time task and avoided obstacles. In addition to the simple reaction time task performance, walking speed was recorded, and participants provided a subjective assessment of cognitive load after each trial. Performance of participants aged less than 60 years were compared with those aged over than 60 years.

RESULTS

Walking significantly reduced performance of the simple reaction time task; carrying out the simple reaction time task while walking significantly reduced walking performance and increased the subjective assessment of cognitive load; and simple reaction time task performance decreased and subjective assessment increased when obstacles were present. Few significant age effects were found.

SIGNIFICANCE

Walking without vision involves a cognitive load that increases when the environment becomes complex. Each of the three methods used is relevant when assessing the cognitive load involved in walking in blind people, and could be useful in rehabilitation intervention. The results obtained allowed recommendations to be suggested for the design of technological mobility devices.

What affects gait performance during walking while texting? A comparison of motor, visual and cognitive factors

Texting on a cell phone disrupts walkers' gait performance. The performance decrement has been attributed to increased motor demand, decreased visual information and increased cognitive load. However, relative contributions of motor, visual and cognitive factors are poorly understood. Here we quantitatively estimated the relative contributions of these factors by comparing multiple walking conditions. Thirty-two adults walked for 20 m, with or without a dual task on the phone. The dual task was either a cognitively demanding digit ordering task or a casual tapping task. Gait performance was assessed using gait speed, stride length, stride time and stride time variability. Results showed that texting negatively impacted gait performance. Importantly, we found that cognitive factor contributed the most, visual factor the least, and motor factor in between. Our findings resolve the inconsistency in the literature and unambiguously show that motor, visual and cognitive factors caused by simultaneous phone use all contribute to gait alterations. Practitioner Summary: Walking performance is typically worsened when a concurrent phone use task such as texting is performed. We found that visual, motor and cognitive factors contributed to this performance decrement with increasing importance. Besides resolving inconsistency among previous reports, we also raised theoretical and practical concerns for phone use during walking.

The quality of visual information about the lower extremities influences visuomotor coordination during virtual obstacle negotiation

Successful negotiation of obstacles during walking relies on the integration of visual information about the environment with ongoing locomotor commands. When information about the body and the environment is removed through occlusion of the lower visual field, individuals increase downward head pitch angle, reduce foot placement precision, and increase safety margins during crossing. However, whether these effects are mediated by loss of visual information about the lower extremities, the obstacle, or both remains to be seen. Here we used a fully immersive, virtual obstacle negotiation task to investigate how visual information about the lower extremities is integrated with information about the environment to facilitate skillful obstacle negotiation. Participants stepped over virtual obstacles while walking on a treadmill with one of three types of visual feedback about the lower extremities: no feedback, end-point feedback, and a link-segment model. We found that absence of visual information about the lower extremities led to an increase in the variability of leading foot placement after crossing. The presence of a visual representation of the lower extremities promoted greater downward head pitch angle during the approach to and subsequent crossing of an obstacle. In addition, having greater downward head pitch was associated with closer placement of the trailing foot to the obstacle, further placement of the leading foot after the obstacle, and higher trailing foot clearance. These results demonstrate that the fidelity of visual information about the lower extremities influences both feedforward and feedback aspects of visuomotor coordination during obstacle negotiation. NEW & NOTEWORTHY Here we demonstrate that visual information about the lower extremities is utilized for precise foot placement and control of safety margins during obstacle negotiation. We also found that when a visual representation of the lower extremities is present, this information is used in the online control of foot trajectory. Together, our results highlight how visual information about the body and the environment is integrated with motor commands for planning and online control of obstacle negotiation.

The pickup of visual information about size and location during approach to an obstacle

The present study investigated differences in the pickup of information about the size and location of an obstacle in the path of locomotion. The main hypothesis was that information about obstacle location is most useful when it is sampled at a specific time during the approach phase, whereas information about obstacle size can be sampled at any point during the last few steps. Subjects approached and stepped over obstacles in a virtual environment viewed through a head-mounted display. In Experiment 1, a horizontal line on the ground indicating obstacle location was visible throughout the trial while information about obstacle height and depth was available only while the subject was passing through a viewing window located at one of four locations along the subject’s path. Subjects exhibited more cautious behavior when the obstacle did not become visible until they were within one step length, but walking behavior was at most weakly affected in the other viewing window conditions. In Experiment 2, the horizontal line indicating obstacle location was removed, such that no information about the obstacle (size or location) was available outside of the viewing window. Subjects adopted a more cautious strategy compared to Experiment 1 and differences between the viewing window conditions and the full vision control condition were observed across several measures. The differences in walking behavior and performance across the two experiments support the hypothesis that walkers have greater flexibility in when they can sample information about obstacle size compared to location. Such flexibility may impact gaze and locomotor control strategies, especially in more complex environments with multiple objects and obstacles.

Effects of acute peripheral/central visual field loss on standing balance

Vision impairments such as age-related macular degeneration (AMD) and glaucoma are among the top risk factors for geriatric falls and falls-related injuries. AMD and glaucoma lead to loss of the central and peripheral visual fields, respectively. This study utilized a custom contact lens model to occlude the peripheral or central visual fields in healthy adults, offering a novel within-subject approach to improve our understanding of the etiology of balance impairments that may lead to an increased fall risk in patients with visual field loss. Two dynamic posturography tests, including an adapted version of the Sensory Organization Test and a virtual reality environment with the visual scene moving sinusoidally, were used to evaluate standing balance. Balance stability was quantified by displacement and time-normalized path length of the center of pressure. Nine young and eleven older healthy adults wore visual field occluding contact lenses during posturography assessments to compare the effects of acute central and peripheral visual field occlusion. The results found that visual field occlusion had greater impact on older adults than young adults, specifically when proprioceptive cues are unreliable. Furthermore, the results suggest that both central and peripheral visions are important in postural control; however, peripheral vision may be more sensitive to movement in the environment.

The impact of mobile phone use on where we look and how we walk when negotiating floor based obstacles

Pedestrians regularly engage with their mobile phone whilst walking. The current study investigated how mobile phone use affects where people look (visual search behaviour) and how they negotiate a floor based hazard placed along the walking path. Whilst wearing a mobile eye tracker and motion analysis sensors, participants walked up to and negotiated a surface height change whilst writing a text, reading a text, talking on the phone, or without a phone. Differences in gait and visual search behaviour were found when using a mobile phone compared to when not using a phone. Using a phone resulted in looking less frequently and for less time at the surface height change, which led to adaptations in gait by negotiating it in a manner consistent with adopting an increasingly cautious stepping strategy. When using a mobile phone, writing a text whilst walking resulted in the greatest adaptions in gait and visual search behaviour compared to reading a text and talking on a mobile phone. Findings indicate that mobile phone users were able to adapt their visual search behaviour and gait to incorporate mobile phone use in a safe manner when negotiating floor based obstacles.

Effects of Age-Related Macular Degeneration on Postural Sway

Purpose: To compare the impact of unilateral vs. bilateral age-related macular degeneration (AMD) on postural sway, and the influence of different visual conditions. The hypothesis of our study was that the impact of AMD will be different between unilateral and bilateral AMD subjects compared to age-matched healthy elderly.

Methods: Postural stability was measured with a platform (TechnoConcept®) in 10 elderly unilateral AMD subjects (mean age: 71.1 ± 4.6 years), 10 elderly bilateral AMD subjects (mean age: 70.8 ± 6.1 years), and 10 healthy age-matched control subjects (mean age: 69.8 ± 6.3 years). Four visual conditions were tested: both eyes viewing condition (BEV), dominant eye viewing (DEV), non-dominant eye viewing (NDEV), and eyes closed (EC). We analyzed the surface area, the length, the mean speed, the anteroposterior (AP), and mediolateral (ML) displacement of the center of pressure (CoP).

Results: Bilateral AMD subjects had a surface area (p < 0.05) and AP displacement of the CoP (p < 0.01) higher than healthy elderly. Unilateral AMD subjects had more AP displacement of the CoP (p < 0.05) than healthy elderly.

Conclusions: We suggest that ADM subjects could have poor postural adaptive mechanisms leading to increase their postural instability. Further studies will aim to improve knowledge on such issue and to develop reeducation techniques in these patients.