Does mobility performance of visually impaired adults improve immediately after orientation and mobility training?

Influence of open-source virtual-reality based gaze training on navigation performance in Retinitis pigmentosa patients in a crossover randomized controlled trial

METHODS

A group of RP patients (n = 8, aged 20-60) participated in a study consisting of two 4-week-phases, both carried out by the same patient group in randomized order: In the 'training phase', participants carried out a Virtual-Reality gaze training for 30 minutes per day; In the 'control phase', no training occurred. Before and after each phase, participants were tasked to move through a randomized real-world obstacle course. Navigation performance in the obstacle course as well as eye-tracking data during the trials were evaluated. The study is registered at the German Clinical Trials Register (DRKS) with the ID DRKS00032628.

RESULTS

On average, the time required to move through the obstacle course decreased by 17.0% after the training phase, the number of collisions decreased by 50.0%. Both effects are significantly higher than those found in the control phase (p < 0.001 for required time, p = 0.0165 for number of collisions), with the required time decreasing by 5.9% and number of collisions decreasing by 10.4% after the control phase. The average visual area observed by participants increases by 4.41% after training, however the effect is not found to be significantly higher than in the control phase (p = 0.394).

CONCLUSION

The performance increase over the training phase significantly surpasses the natural learning effect found in the control phase, suggesting that Virtual-Reality based gaze training can have a positive effect on real-world navigation tasks for patients with RP. The training is available as work-in-progress open-source software.

Multi-luminance Mobility Testing Endpoint

An individual's functional vision may be measured via visual assessment and performance on mobility tasks. Since traditional mobility performance tests neglect to examine the effects of illumination on performance, the multi-luminance mobility test (MLMT) was designed to quantitatively assess the effects of illumination levels on an individual's mobility performance. In this chapter, we describe how the MLMT is conducted and scored in order to properly evaluate a participant's mobility under various light conditions.

Development of Virtual Reality Walking Collision Detection Test on Head-mounted display

Detecting and avoiding collisions during walking is critical for safe mobility. To determine the effectiveness of clinical interventions, a realistic objective outcome measure is needed. A real-world obstacle course with moving hazards has numerous limitations (e.g., safety concerns of physical collision, inability to control events, maintaining event consistency, and event randomization). Virtual reality (VR) platforms may overcome such limitations. We developed a VR walking collision detection test using a standalone head-mounted display (HMD, Meta Quest 2) with the Unity 3D engine to enable subjects' physical walking within a VR environment (i.e., a busy shopping mall). The performance measures focus on the detection and avoidance of potential collisions, where a pedestrian may (or may not) walks toward a collision with the subject, while various non-colliding pedestrians are presented simultaneously. The physical space required for the system was minimized. During the development, we addressed expected and unexpected hurdles, such as mismatch of visual perception of VR space, limited field of view (FOV) afforded by the HMD, design of pedestrian paths, design of the subject task, handling of subject's response (detection or avoidance behavior), use of mixed reality (MR) for walking path calibration. We report the initial implementation of the HMD VR walking collision detection and avoidance scenarios that showed promising potential as clinical outcome measures.

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.

Longitudinal Trends in Case Histories and Rehabilitative Device Assessments at Low Vision Examinations

SIGNIFICANCE

Understanding longitudinal changes in why individuals frequent low-vision clinics is crucial for ensuring that patient care keeps current with changing technology and changing lifestyles. Among other findings, our results suggest that reading remains a prevailing patient complaint, with shifting priorities toward technology-related topics.

PURPOSE

This study aimed to understand changes in patient priorities and patient care in low vision over the past decade.

METHODS

We conducted a retrospective study of examination records (2009 to 2019, 3470 examinations) from two U.S. low-vision clinics. Automated word searches summarized two properties of the records: topics discussed during the case history and types of rehabilitative devices assessed. Logistic regression was used to model the effects of examination year, patient age, patient sex, and level of visual impairment.

RESULTS

Collapsing across all years, the most common topic discussed was reading (78%), followed by light-related topics (71%) and technology (59%). Whereas the odds of discussing reading trended downward over the decade (odds ratio, 0.57; P = .03), technology, social interaction, mobility, and driving trended upward (odds ratios, 4.53, 3.31, 2.71, and 1.95; all P 's < 0.001). The most frequently assessed devices were tinted lenses (95%). Over time, video magnifier and spectacle assessments trended downward (odds ratios, 0.64 and 0.72; P = .004, 0.04), whereas assessments of other optical aids increased. The data indicate several consistent differences among patient demographics.

CONCLUSIONS

Reading is likely to remain a prevailing patient complaint, but an increase in technology-related topics suggests shifting priorities, particularly in younger demographics. "Low-tech" optical aids have remained prominent in low-vision care even as "high-tech" assistive devices in the marketplace continue to advance.

Concept Mapping to Identify Content for a Performance-Based Measure of Low Luminance Vision-Related Activities of Daily Living

Purpose

The purpose of this study was to identify low luminance activities of daily living (ADL) relevant to adults with vision impairment using a concept-mapping approach.

Methods

“Group concept mapping” was utilized to identify specific ADLs that persons with vision impairment find challenging under low light conditions. In the first “brainstorming” phase, 24 adults with vision impairment from a range of eye conditions (mean age = 73 years, SD = 14 years) and 26 international low vision experts (mean experience = 22, SD = 11 years) generated statements to the focus prompt, “Thinking as broadly as possible, generate a list of statements detailing specific day-to-day activities a person with vision impairment might find challenging under low light conditions, such as in a poorly lit room or outside at dusk.” In the second phase, participants sorted activities by similarity and rated the importance of each activity. Multidimensional scaling and hierarchical cluster analysis were applied to produce concept maps showing clusters of prioritized activities.

Results

One hundred thirteen unique ideas/activities were generated, rated and sorted. Eight clusters were identified (from highest to lowest importance): hazard detection and safety outside; social interactions; navigation; near reading; selfcare and safety at home; distance spotting; searching around the home; and cooking and cleaning.

Conclusions

The conceptual framework and low luminance ADLs identified (the most important being hazard detection and safety outside, and social interactions) provide a basis for developing a performance-based measure of low luminance visual function.

Translational Relevance

A performance-based measure of low luminance vision-related ADLs is required for comprehensively and objectively assessing efficacy of eye treatments and low vision rehabilitation outcomes in adults with vision impairment.

Functional evaluation in inherited retinal disease

Functional assessments are a fundamental part of the clinical evaluation of patients with inherited retinal diseases (IRDs). Their importance and impact have become increasingly notable, given the significant breadth and number of clinical trials and studies investigating multiple avenues of intervention across a wide range of IRDs, including gene, pharmacological and cellular therapies. Moreover, the fact that many clinical trials are reporting improvements in vision, rather than the previously anticipated structural stability/slowing of degeneration, makes functional evaluation of primary relevance. In this review, we will describe a range of methods employed to characterise retinal function and functional vision, beginning with tests variably included in the clinic, such as visual acuity, electrophysiological assessment and colour discrimination, and then discussing assessments often reserved for clinical trials/research studies such as photoaversion testing, full-field static perimetry and microperimetry, and vision-guided mobility testing; addressing perimetry in greatest detail, given it is commonly a primary outcome metric. We will focus on how these tests can help diagnose and monitor particular genotypes, also noting their limitations/challenges and exploring analytical methodologies for better exploiting functional measurements, as well as how they facilitate patient inclusion and stratification in clinical trials and serve as outcome measures.

Measuring mobility performance: experience gained in designing a mobility course

BACKGROUND

This paper reviews the most common methods of measuring and scoring orientation and mobility (O and M) and the effects of visual impairment on O and M. We discuss the difficulties inherent in designing a 'real-world' course to measure O and M and we describe the course that we finally used.

METHODS

Thirty-five participants in two age groups, with low vision due to a variety of disorders, took part in mobility trials on the final version of the course. Aspects of visual function were measured.

RESULTS

Factor analysis indicated that mobility errors, visual detection distance and visual identification distance were grouped with measures of visual acuity, contrast sensitivity and Humphrey visual field mean deviation, while preferred walking speed and walking speed were separately grouped. Humphrey pattern standard deviation did not group with any other measure and neither did percentage preferred walking speed. This study is in agreement with other studies that visual field and contrast sensitivity, sometimes with low contrast visual acuity, were the best clinical visual predictors of mobility performance. Based on our experiences we present a number of recommendations for designing courses for assessing mobility.

CONCLUSIONS

For future studies, it would behove researchers to include a range of mobility measures, until further understanding is gained about how they are interrelated and contribute information on the relationship among mobility, vision and other individual factors.

Vision and self‐reported mobility performance in patients with low vision

BACKGROUND

As vision plays a significant role in mobility performance, it is usual to refer low vision patients, particularly those who complain of mobility difficulties, for orientation and mobility (O&M) training to help them maintain safe independent travel. Our study aimed to determine whether there was a relationship between measures of vision and self-reported mobility, and the applicability of a patient-based mobility assessment in patients with heterogeneous causes of visual loss.

METHOD

We assessed the high and low contrast visual acuity, visual field and scanning ability of 30 patients with low vision. A validated mobility questionnaire was used to assess the participants' perceived visual ability for independent mobility.

RESULTS

Vision was significantly correlated with self-reported mobility performance, however, visual field was a significant predictor accounting for 56.5 per cent of the variance. The instrument was well constructed with valid content and high reliability scores.

CONCLUSIONS

Self-reported mobility performance together with measures of vision could be used as a guide to refer patients for O&M training. The patient-based assessment instrument was valid to measure perceived visual ability for independent mobility in patients with heterogeneous causes of visual loss.

Low vision rehabilitation for better quality of life in visually impaired adults

BACKGROUND

Low vision rehabilitation aims to optimise the use of residual vision after severe vision loss, but also aims to teach skills in order to improve visual functioning in daily life. Other aims include helping people to adapt to permanent vision loss and improving psychosocial functioning. These skills promote independence and active participation in society. Low vision rehabilitation should ultimately improve quality of life (QOL) for people who have visual impairment.

OBJECTIVES

To assess the effectiveness of low vision rehabilitation interventions on health-related QOL (HRQOL), vision-related QOL (VRQOL) or visual functioning and other closely related patient-reported outcomes in visually impaired adults.

SEARCH METHODS

We searched relevant electronic databases and trials registers up to 18 September 2019.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) investigating HRQOL, VRQOL and related outcomes of adults, with an irreversible visual impairment (World Health Organization criteria). We included studies that compared rehabilitation interventions with active or inactive control.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 44 studies (73 reports) conducted in North America, Australia, Europe and Asia. Considering the clinical diversity of low vision rehabilitation interventions, the studies were categorised into four groups of related intervention types (and by comparator): (1) psychological therapies and/or group programmes, (2) methods of enhancing vision, (3) multidisciplinary rehabilitation programmes, (4) other programmes. Comparators were no care or waiting list as an inactive control group, usual care or other active control group. Participants included in the reported studies were mainly older adults with visual impairment or blindness, often as a result of age-related macular degeneration (AMD). Study settings were often hospitals or low vision rehabilitation services. Effects were measured at the short-term (six months or less) in most studies. Not all studies reported on funding, but those who did were supported by public or non-profit funders (N = 31), except for two studies. Compared to inactive comparators, we found very low-certainty evidence of no beneficial effects on HRQOL that was imprecisely estimated for psychological therapies and/or group programmes (SMD 0.26, 95% CI -0.28 to 0.80; participants = 183; studies = 1) and an imprecise estimate suggesting little or no effect of multidisciplinary rehabilitation programmes (SMD -0.08, 95% CI -0.37 to 0.21; participants = 183; studies = 2; I2 = 0%); no data were available for methods of enhancing vision or other programmes. Regarding VRQOL, we found low- or very low-certainty evidence of imprecisely estimated benefit with psychological therapies and/or group programmes (SMD -0.23, 95% CI -0.53 to 0.08; studies = 2; I2 = 24%) and methods of enhancing vision (SMD -0.19, 95% CI -0.54 to 0.15; participants = 262; studies = 5; I2 = 34%). Two studies using multidisciplinary rehabilitation programmes showed beneficial but inconsistent results, of which one study, which was at low risk of bias and used intensive rehabilitation, recorded a very large and significant effect (SMD: -1.64, 95% CI -2.05 to -1.24), and the other a small and uncertain effect (SMD -0.42, 95%: -0.90 to 0.07). Compared to active comparators, we found very low-certainty evidence of small or no beneficial effects on HRQOL that were imprecisely estimated with psychological therapies and/or group programmes including no difference (SMD -0.09, 95% CI -0.39 to 0.20; participants = 600; studies = 4; I2 = 67%). We also found very low-certainty evidence of small or no beneficial effects with methods of enhancing vision, that were imprecisely estimated (SMD -0.09, 95% CI -0.28 to 0.09; participants = 443; studies = 2; I2 = 0%) and multidisciplinary rehabilitation programmes (SMD -0.10, 95% CI -0.31 to 0.12; participants = 375; studies = 2; I2 = 0%). Concerning VRQOL, low-certainty evidence of small or no beneficial effects that were imprecisely estimated, was found with psychological therapies and/or group programmes (SMD -0.11, 95% CI -0.24 to 0.01; participants = 1245; studies = 7; I2 = 19%) and moderate-certainty evidence of small effects with methods of enhancing vision (SMD -0.24, 95% CI -0.40 to -0.08; participants = 660; studies = 7; I2 = 16%). No additional benefit was found with multidisciplinary rehabilitation programmes (SMD 0.01, 95% CI -0.18 to 0.20; participants = 464; studies = 3; I2 = 0%; low-certainty evidence). Among secondary outcomes, very low-certainty evidence of a significant and large, but imprecisely estimated benefit on self-efficacy or self-esteem was found for psychological therapies and/or group programmes versus waiting list or no care (SMD -0.85, 95% CI -1.48 to -0.22; participants = 456; studies = 5; I2 = 91%). In addition, very low-certainty evidence of a significant and large estimated benefit on depression was found for psychological therapies and/or group programmes versus waiting list or no care (SMD -1.23, 95% CI -2.18 to -0.28; participants = 456; studies = 5; I2 = 94%), and moderate-certainty evidence of a small benefit versus usual care (SMD -0.14, 95% CI -0.25 to -0.04; participants = 1334; studies = 9; I2 = 0%). ln the few studies in which (serious) adverse events were reported, these seemed unrelated to low vision rehabilitation.

AUTHORS' CONCLUSIONS

In this Cochrane Review, no evidence of benefit was found of diverse types of low vision rehabilitation interventions on HRQOL. We found low- and moderate-certainty evidence, respectively, of a small benefit on VRQOL in studies comparing psychological therapies or methods for enhancing vision with active comparators. The type of rehabilitation varied among studies, even within intervention groups, but benefits were detected even if compared to active control groups. Studies were conducted on adults with visual impairment mainly of older age, living in high-income countries and often having AMD. Most of the included studies on low vision rehabilitation had a short follow-up, Despite these limitations, the consistent direction of the effects in this review towards benefit justifies further research activities of better methodological quality including longer maintenance effects and costs of several types of low vision rehabilitation. Research on the working mechanisms of components of rehabilitation interventions in different settings, including low-income countries, is also needed.

Mobility-Related Gaze Training in Individuals With Glaucoma: A Proof-of-Concept Study

Purpose

Older adults with glaucoma show inappropriate gaze strategies during routine mobility tasks. Furthermore, glaucoma is a risk factor for falling and colliding with objects when walking. However, effective interventions to rectify these strategies and prevent these adverse events are scarce. We designed a gaze training program with the goal of providing proof-of-concept that we could modify mobility-related gaze behavior in this population.

Methods

A total of 13 individuals with moderate glaucoma participated in this study. We taught participants general and task-specific gaze strategies over two 1-hour sessions. To determine the efficacy of this gaze training program, participants performed walking tasks that required accurate foot placement onto targets and circumventing obstacles before and after training. We used a mobile eye tracker to quantify gaze and a motion-capture system to quantify body movement.

Results

After training, we found changes in the timing between gaze shifts away from targets relative to stepping on them (P < 0.05). In the obstacle negotiation task, we found a greater range of gaze shifts early in walking trials and changes in the timing between gaze shifts away from obstacles after training (P < 0.05), each suggesting better route planning. A posttraining reduction in foot-placement error and obstacle collisions accompanied these changes (P < 0.05).

Conclusions

Our results demonstrated that it is possible to modify mobility-related gaze behavior and mobility performance in older adults with glaucoma.

Translational Relevance

This study provides proof-of-concept for a gaze training program for glaucoma. A larger, randomized controlled trial is warranted.

Variability in Reactions to Instructional Guidance during Smartphone-Based Assisted Navigation of Blind Users

'Turn slightly to the left' the navigational system announces, with the aim of directing a blind user to merge into a corridor. Yet, due to long reaction time, the user turns too late and proceeds into the wrong hallway. Observations of such user behavior in real-world navigation settings motivate us to study the manner in which blind users react to the instructional feedback of a turn-by-turn guidance system. We found little previous work analyzing the extent of the variability among blind users in reaction to different instructional guidance during assisted navigation. To gain insight into how navigational interfaces can be better designed to accommodate the information needs of different users, we conduct a data-driven analysis of reaction variability as defined by motion and timing measures. Based on continuously tracked user motion during real-world navigation with a deployed system, we find significant variability between users in their reaction characteristics. Specifically, the statistical analysis reveals significant variability during the crucial elements of the navigation (e.g., turning and encountering obstacles). With the end-user experience in mind, we identify the need to not only adjust interface timing and content to each user's personal walking pace, but also their individual navigation skill and style. The design implications of our study inform the development of assistive systems which consider such user-specific behavior to ensure successful navigation.

External relative to internal attentional focus enhances motor performance and learning in visually impaired individuals

Background: Research has demonstrated the advantages of an external relative to internal focus of attention for enhancing motor performance and learning across diverse tasks, contexts and populations. However, research has yet to examine whether this finding holds true for individuals who have a major visual impairment in discrete and locomotion-based continuous motor tasks.Methods: In experiment 1, twenty-four visually impaired participants were asked to kick a soccer ball with their dominant foot to a target 7 meters away. Participants performed 10 trials within an internal focus (concentration on inside of the foot), external focus (concentration on the ball), and control (no focus instructions) conditions, in a counterbalanced order. In experiment 2, thirty-nine visually impaired adults were asked to ride a rehabilitation Pedalo for a distance of 7 meters. Participants were randomly assigned to either an internal focus (focus on the feet), external focus (focus on the platform), or control (no focus instructions) group. Retention and transfer tests were conducted on day 2.Results: An external focus resulted in more accurate kicks and faster pedalo movement times compared to an internal focus.Conclusions: These findings indicate that visual information does not mediate external focus benefits for motor performance and learning.Implications for RehabilitationPractitioners should use instructions that encourage visually impaired individuals who are going through rehabilitation to adopt an appropriate focus of attention for enhancing motor performance and learning of discrete or locomotion-based motor skills.Instructions that foster an external focus, relative to an internal focus, enhances performance of both discrete and continuous motor skills in individuals with visual impairment.

Effectiveness of Assistive Technologies for Low Vision Rehabilitation: A Systematic Review

A systematic review of all types of assistive devices indicated the need for more research related to performance measurements and the effectiveness of vision rehabilitation devices.

How body motion influences echolocation while walking

This study investigated the influence of body motion on an echolocation task. We asked a group of blindfolded novice sighted participants to walk along a corridor, made with plastic sound-reflecting panels. By self-generating mouth clicks, the participants attempted to understand some spatial properties of the corridor, i.e. a left turn, a right turn or a dead end. They were asked to explore the corridor and stop whenever they were confident about the corridor shape. Their body motion was captured by a camera system and coded. Most participants were able to accomplish the task with the percentage of correct guesses above the chance level. We found a mutual interaction between some kinematic variables that can lead to optimal echolocation skills. These variables are head motion, accounting for spatial exploration, the motion stop-point of the person and the amount of correct guesses about the spatial structure. The results confirmed that sighted people are able to use self-generated echoes to navigate in a complex environment. The inter-individual variability and the quality of echolocation tasks seems to depend on how and how much the space is explored.

Quantifying the impact on navigation performance in visually impaired: Auditory information loss versus information gain enabled through electronic travel aids

This study’s purpose was to analyze and quantify the impact of auditory information loss versus information gain provided by electronic travel aids (ETAs) on navigation performance in people with low vision. Navigation performance of ten subjects (age: 54.9±11.2 years) with visual acuities >1.0 LogMAR was assessed via the Graz Mobility Test (GMT). Subjects passed through a maze in three different modalities: ‘Normal’ with visual and auditory information available, ‘Auditory Information Loss’ with artificially reduced hearing (leaving only visual information), and ‘ETA’ with a vibrating ETA based on ultrasonic waves, thereby facilitating visual, auditory, and tactile information. Main performance measures comprised passage time and number of contacts. Additionally, head tracking was used to relate head movements to motion direction. When comparing ‘Auditory Information Loss’ to ‘Normal’, subjects needed significantly more time (p<0.001), made more contacts (p<0.001), had higher relative viewing angles (p = 0.002), and a higher percentage of orientation losses (p = 0.011). The only significant difference when comparing ‘ETA’ to ‘Normal’ was a reduced number of contacts (p<0.001). Our study provides objective, quantifiable measures of the impact of reduced hearing on the navigation performance in low vision subjects. Significant effects of ‘Auditory Information Loss’ were found for all measures; for example, passage time increased by 17.4%. These findings show that low vision subjects rely on auditory information for navigation. In contrast, the impact of the ETA was not significant but further analysis of head movements revealed two different coping strategies: half of the subjects used the ETA to increase speed, whereas the other half aimed at avoiding contacts.

Novel mobility test to assess functional vision in patients with inherited retinal dystrophies

IMPORTANCE

This novel endpoint tracks functional vision changes in patients with inherited retinal dystrophies (IRDs) over time.

BACKGROUND

The aims of the study were to determine whether a multi-luminance mobility test (MLMT) can detect functional vision changes over time in subjects with IRDs and to assess natural history and potential effects of investigational agents.

DESIGN

This is a prospective, observational study.

PARTICIPANTS

Sixty-two subjects were enrolled. Sixty (29 normal sighted and 31 visually impaired) were eligible; 54 (28 visually impaired and 26 normal-sighted) completed all testing visits.

METHODS

Subjects navigated MLMT courses three times over 1 year. At each visit, subjects completed testing using individual eyes, and both eyes, at up to nine standardized, increasing luminance levels (range 1 to 400 lux). Accuracy and speed were evaluated and compared with visual acuity (VA), visual field (VF) and a visual function questionnaire.

MAIN OUTCOME MEASURES

Accuracy and speed of normal and visually impaired subjects on MLMT, and reliability and content validity of MLMT were the main outcome measures.

RESULTS

MLMT distinguished normal-sighted from visually impaired subjects. All control subjects passed all MLMT attempts at all tested light levels. Visually impaired subjects' performance varied widely; some declined over 1 year. Performance declined markedly below certain VA and VF thresholds. Concordance on performance on two baseline visits was high: correlations for accuracy were 94% and 98% for lowest common and highest common lux levels.

CONCLUSIONS AND RELEVANCE

MLMT differentiated visually impaired from control populations and, in visually impaired subjects, identified a range of performances; and tracked performance declines over time, consistent with these progressive conditions.

Role of vision in sighted and blind soccer players in adapting to an unstable balance task

This study tested whether a compensatory hypothesis exists on postural control during standing unstable balance tasks comparing blind soccer players (n = 7) to sighted soccer players (n = 15) and sighted sedentary individuals (n = 6). All subjects performed a pre-test, a training of ten practice trials on a single day, and a post-test balance test. All tests were performed on an unstable surface placed on a force platform and under closed-eyes conditions, and a final test was performed with open eyes. Balance performance was assessed by resultant distance (RD) and the magnitude of mean velocity (MV) of the centre of pressure (CoP) displacement, and EMG signals from the gastrocnemius lateralis, tibialis anterior, rectus femoris, and peroneus longus were measured with surface electromyography. Principal component analysis (PCA) on EMG muscular activation was used to assess EMG pattern differences during the balance tasks. All groups improved their performance, obtaining low scores for the closed-eyes condition balance task after the training period in RD, VM, and aids received to keep balance in the novel task, and no differences were found between groups or in interaction effects. Sighted individuals and the control group showed significantly lower RD and VM scores under open-eyes conditions than blind participants. As regards neuromuscular behaviour, three principal patterns explained 84.15% of the variability in the measured data. The theoretical improvement of the other senses caused by visual deprivation does not allow blind individuals to obtain better balance than sighted individuals under closed-eyes conditions, thereby reinforcing the prominent role of vision in integrating and processing the other sensory inputs. In addition, blind individuals seem to increase their muscular co-activation as a safety strategy, but this behaviour is not different to that shown by sighted people under closed-eyes conditions.

Eye Movement Training and Suggested Gaze Strategies in Tunnel Vision - A Randomized and Controlled Pilot Study

PURPOSE

Degenerative retinal diseases, especially retinitis pigmentosa (RP), lead to severe peripheral visual field loss (tunnel vision), which impairs mobility. The lack of peripheral information leads to fewer horizontal eye movements and, thus, diminished scanning in RP patients in a natural environment walking task. This randomized controlled study aimed to improve mobility and the dynamic visual field by applying a compensatory Exploratory Saccadic Training (EST).

METHODS

Oculomotor responses during walking and avoiding obstacles in a controlled environment were studied before and after saccade or reading training in 25 RP patients. Eye movements were recorded using a mobile infrared eye tracker (Tobii glasses) that measured a range of spatial and temporal variables. Patients were randomly assigned to two training conditions: Saccade (experimental) and reading (control) training. All subjects who first performed reading training underwent experimental training later (waiting list control group). To assess the effect of training on subjects, we measured performance in the training task and the following outcome variables related to daily life: Response Time (RT) during exploratory saccade training, Percent Preferred Walking Speed (PPWS), the number of collisions with obstacles, eye position variability, fixation duration, and the total number of fixations including the ones in the subjects' blind area of the visual field.

RESULTS

In the saccade training group, RTs on average decreased, while the PPWS significantly increased. The improvement persisted, as tested 6 weeks after the end of the training. On average, the eye movement range of RP patients before and after training was similar to that of healthy observers. In both, the experimental and reading training groups, we found many fixations outside the subjects' seeing visual field before and after training. The average fixation duration was significantly shorter after the training, but only in the experimental training condition.

CONCLUSIONS

We conclude that the exploratory saccade training was beneficial for RP patients and resulted in shorter fixation durations after the training. We also found a significant improvement in relative walking speed during navigation in a real-world like controlled environment.

Outdoor difficulties experienced by a group of visually impaired Iranian people

Propose

A qualitative approach using semi-structured individual interviews was used to elicit common outdoor difficulties in individuals with visual impairment.

Methods

Interviews were recorded and then transcribed verbatim into text for thematic analysis. Twenty legally-blind individuals aged 34.25 ± 2.41 years with different etiologies were included in this study.

Results

All participants had experienced some sort of difficulty in outdoor environments. The most important problems as perceived by the participants are installation of tactile ground surface indicators, unsafe sidewalks, existence of obstacles on sidewalks, difficulty reading bus numbers, disorientation, fear of falling, recognition of faces, inability to read street names, the presence of spaces between platforms and buses, walking into glass doors, crossing streets, and the risk of Arial barriers.

Conclusions

As a visually impaired person might say, sidewalks can be the most dangerous of places. Appropriate urban modification can be very beneficial.

FLORA™: Phase I development of a functional vision assessment for prosthetic vision users

BACKGROUND

Research groups and funding agencies need a functional assessment suitable for an ultra-low vision population to evaluate the impact of new vision-restoration treatments. The purpose of this study was to develop a pilot assessment to capture the functional visual ability and well-being of subjects whose vision has been partially restored with the Argus II Retinal Prosthesis System.

METHODS

The Functional Low-Vision Observer Rated Assessment (FLORA) pilot assessment involved a self-report section, a list of functional visual tasks for observation of performance and a case narrative summary. Results were analysed to determine whether the interview questions and functional visual tasks were appropriate for this ultra-low vision population and whether the ratings suffered from floor or ceiling effects. Thirty subjects with severe to profound retinitis pigmentosa (bare light perception or worse in both eyes) were enrolled in a clinical trial and implanted with the Argus II System. From this population, 26 subjects were assessed with the FLORA. Seven different evaluators administered the assessment.

RESULTS

All 14 interview questions were asked. All 35 tasks for functional vision were selected for evaluation at least once, with an average of 20 subjects being evaluated for each test item. All four rating options—impossible (33 per cent), difficult (23 per cent), moderate (24 per cent) and easy (19 per cent)—were used by the evaluators. Evaluators also judged the amount of vision they observed the subjects using to complete the various tasks, with 'vision only' occurring 75 per cent on average with the System ON, and 29 per cent with the System OFF.

CONCLUSION

The first version of the FLORA was found to contain useful elements for evaluation and to avoid floor and ceiling effects. The next phase of development will be to refine the assessment and to establish reliability and validity to increase its value as an assessment tool for functional vision and well-being.

Static and dynamic postural control in low-vision and normal-vision adults

OBJECTIVE

This study aimed to evaluate the influence of reduced visual information on postural control by comparing low-vision and normal-vision adults in static and dynamic conditions.

METHODS

Twenty-five low-vision subjects and twenty-five normal sighted adults were evaluated for static and dynamic balance using four protocols: 1) the Modified Clinical Test of Sensory Interaction on Balance on firm and foam surfaces with eyes opened and closed; 2) Unilateral Stance with eyes opened and closed; 3) Tandem Walk; and 4) Step Up/Over.

RESULTS

The results showed that the low-vision group presented greater body sway compared with the normal vision during balance on a foam surface (p≤0.001), the Unilateral Stance test for both limbs (p≤0.001), and the Tandem Walk test. The low-vision group showed greater step width (p≤0.001) and slower gait speed (p≤0.004). In the Step Up/Over task, low-vision participants were more cautious in stepping up (right p≤0.005 and left p≤0.009) and in executing the movement (p≤0.001).

CONCLUSION

These findings suggest that visual feedback is crucial for determining balance, especially for dynamic tasks and on foam surfaces. Low-vision individuals had worse postural stability than normal-vision adults in terms of dynamic tests and balance on foam surfaces.

Orientation and mobility assessment in retinal prosthetic clinical trials

PURPOSE

The purpose of this study was to develop an orientation and mobility (O&M) assessment protocol to implement in subjects who have been implanted with an artificial silicon retina (ASR), and to use this experience to propose a research agenda for O&M with prosthetic vision.

METHODS

A controlled and naturalistic assessment was developed that included walking a prescribed obstacle course and travel to and from a hospital cafeteria. Subjects were tested before and 3 and 6 months after being implanted with the ASR. Outcome measures were walking speed and number of contacts with obstacles. The experiences from this study led to a proposed research agenda in O&M.

RESULTS

Eight subjects with retinitis pigmentosa participated in this study. The vision status of the subjects ranged from <20/1600 to 20/80 visual acuity and visual fields of <5 to 40°. Using a repeated-measures analysis of variance, no differences were found in the primary outcome measures. Four subjects were observed to have reduced mobility after implantation. Three subjects self-reported enhancements of travel after implantation, but this enhancement was not observed.

CONCLUSIONS

This study demonstrates that mobility might not be improved with prosthetic vision. The proposed research agenda emphasizes the importance of developing individualized assessments, identifying specific items of orientation rather than mobility for measuring the effect of prosthetic vision, and to develop and evaluate instructional programs that may be needed to obtain the full benefit of the technology.

The development of an indoor mobility course for the evaluation of electronic mobility aids for persons who are visually impaired

PURPOSE

To develop a suitable mobility course for the assessment of mobility performance as part of a user evaluation of Electronic Mobility Aids (EMA) aimed at obstacle detection and orientation.

METHOD

A review of the literature led to a list of critical factors for the assessment of mobility performance of persons who are visually impaired. Based upon that list, method, test situations, and determining elements were selected and presented to Dutch orientation and mobility experts. Due to expert advice and a pilot study, minor changes were made and the final version was used for the evaluation of two EMA by eight persons who are visually impaired.

RESULTS

The results of the literature study are summarized in an overview of critical factors for the assessment of the mobility performance of persons who are visually impaired. Applied to the requirements of the above mentioned user evaluation a replicable indoor mobility course has been described in detail and tested.

CONCLUSION

Based upon evidence from literature an indoor mobility course has been developed, which was sensitive to assess differences in mobility incidents and obstacle detection when using an EMA compared to the regular mobility aid. Experts' opinion confirmed its face and content validity.

User evaluation of two electronic mobility aids for persons who are visually impaired: a quasi-experimental study using a standardized mobility course

This study was conducted to enhance insight into the functionality, usability, and efficacy of two systematically selected Electronic Mobility Aids (EMA) aimed at obstacle detection and orientation. Eight persons who are visually impaired participated in a user evaluation of the UltraCane and the Miniguide. The participants' mobility performance was observed while completing a standardized indoor mobility course with their regular mobility aid, then with each EMA, and assessed in terms of speed, Percentage Preferred Walking Speed (PPWS), type and number of mobility incidents made. Interviews were administered to ascertain users' satisfaction with the functionality, effectiveness and specific features of the assistive devices. Walking speed and PPWS declined when using an EMA compared to the long cane. The mean total number of previously defined mobility incidents decreased significantly and also the type of mobility incidents changed. Generally, participants were quite satisfied with the use of the EMA, and detailed advantageous as well as disadvantageous aspects concerning functionality and certain features of both devices. The UltraCane and the Miniguide have proven to be effective on an indoor mobility course. Individual users' characteristics and preferences appear to be critical for their appraisal of the devices.

Usefulness and acceptability of a standardised orientation and mobility training for partially-sighted older adults using an identification cane

BACKGROUND

Orientation and mobility (O&M) training in using an identification (ID) cane is provided to partially-sighted older adults to facilitate independent functioning and participation in the community. Recently, a protocolised standardised O&M-training in the use of the ID cane was developed in The Netherlands. The purpose of this study is to assess the usefulness and acceptability of both the standardised training and the regular training for participants and O&M-trainers in a randomised controlled trial (NCT00946062).

METHODS

The standardised O&M-training consists of two structured face-to-face sessions and one telephone follow-up, in which, in addition to the regular training, self-management and behavioural change techniques are applied. Questionnaires and interviews were used to collect data on the training's usefulness, e.g. the population reached, self-reported benefits or achievements, and acceptability, e.g. the performance of the intervention according to protocol and participants' exposure to and engagement in the training.

RESULTS

Data was collected from 29 O&M-trainers and 68 participants. Regarding the self-reported benefits, outcomes were comparable for the standardised training and the regular training according the trainers and participants e.g., about 85% of the participants in both groups experienced benefits of the cane and about 70% gained confidence in their capabilities. Participants were actively involved in the standardised training. Nearly 40% of the participants in the standardised training group was not exposed to the training according to protocol regarding the number of sessions scheduled and several intervention elements, such as action planning and contracting.

CONCLUSIONS

The standardised and regular O&M-training showed to be useful and mostly acceptable for the partially-sighted older adults and trainers. Yet, a concern is the deviation from the protocol of the standardised O&M-training by the O&M-trainers regarding distinguishing elements such as action planning. Overall, participants appreciated both trainings and reported benefit.

Orientation and mobility training for partially-sighted older adults using an identification cane: a systematic review

Objective: This study aimed to provide an overview of the development, content, feasibility, and effectiveness of existing orientation and mobility training programmes in the use of the identification cane.

Data sources: A systematic bibliographic database search in PubMed, PsychInfo, ERIC, CINAHL and the Cochrane Library was performed, in combination with the expert consultation (n = 42; orientation and mobility experts), and hand-searching of reference lists.

Review methods: Selection criteria included a description of the development, the content, the feasibility, or the effectiveness of orientation and mobility training in the use of the identification cane. Two reviewers independently agreed on eligibility and methodological quality. A narrative/qualitative data analysis method was applied to extract data from obtained documents.

Results: The sensitive database search and hand-searching of reference lists revealed 248 potentially relevant abstracts. None met the eligibility criteria. Expert consultation resulted in the inclusion of six documents in which the information presented on the orientation and mobility training in the use of the identification cane was incomplete and of low methodological quality.

Conclusion: Our review of the literature showed a lack of well-described protocols and studies on orientation and mobility training in identification cane use.

Orientation and mobility training for adults with low vision

BACKGROUND

Orientation and mobility (O&M) training is provided to people who are visually impaired to help them maintain travel independence. It teaches them new orientation and mobility skills to compensate for reduced visual information.

OBJECTIVES

The objective of this review was to assess the effects of O&M training, with or without associated devices, for adults with low vision.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, 2010, Issue 3), MEDLINE (January 1950 to March 2010), EMBASE (January 1980 to March 2010), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to March 2010), System for Information on Grey Literature in Europe (OpenSIGLE) (March 2010), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (March 2010), ClinicalTrials.gov (http://clinicaltrials.gov) (March 2010), ZETOC (March 2010) and the reference lists of retrieved articles. There were no language or date restrictions in the search for trials. The electronic databases were last searched on 31 March 2010.

SELECTION CRITERIA

We planned to include randomised or quasi-randomised trials comparing O&M training with no training in adults with low vision.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the search results for eligibility, evaluated study quality and extracted the data.

MAIN RESULTS

Two small studies satisfied the inclusion criteria. They were consecutive phases of development of the same training curriculum and assessment tool. The intervention was administered by a volunteer on the basis of written and oral instruction. In both studies the randomisation technique was inadequate, being based on alternation, and masking was not achieved. Training had no effect in the first study but tended to be beneficial in the second but not to a statistically significant extent. Reasons for differences between studies may have been: the high scores obtained in the first study, suggestive of little need for training and small room for further improvement (a ceiling effect), and the refinement of the curriculum allowing better tailoring to patients' specific needs and characteristics, in the second study.

AUTHORS' CONCLUSIONS

The review found two small quasi-randomised trials with similar methods, comparing training to physical exercise and assessing O&M physical performance by means of a volunteer or a professional, which were unable to demonstrate a difference. Therefore, there is little evidence on which type of O&M training is better for people with low vision who have specific characteristics and needs. Orientation and mobility instructors and scientists should plan randomised controlled trials (RCTs) to compare the effectiveness of different types of O&M training. A consensus is needed on the adoption of standard measurement instruments of mobility performance which are proven to be reliable and sensitive to the diverse mobility needs of people with low vision. For this purpose, questionnaires and performance-based tests may represent different tools that explore people with low vision's subjective experience or their objective functioning, respectively. In fact, it has to be observed that low vision rehabilitation research is increasingly shifting towards the use of quality of life questionnaires as an outcome measure, sometimes with the aim to study complex and multidisciplinary interventions including different types of education and support, of which O&M can be a component. An example of this is an ongoing cluster RCT conducted by Zijlstra et al. in The Netherlands. This trial is designed to compare standardised O&M training with usual O&M care not only for its effectiveness, but also its applicability and acceptability. This study adopts validated questionnaires for patients' subjective assessment of performance during activities of daily living. As performance assessment does not need to be made by an O&M trainer, this allows for masking of assessors and a patient-centred outcome measure.

Extended wearing trial of Trifield lens device for 'tunnel vision'

Severe visual field constriction (tunnel vision) impairs the ability to navigate and walk safely. We evaluated Trifield glasses as a mobility rehabilitation device for tunnel vision in an extended wearing trial. Twelve patients with tunnel vision (5-22 degrees wide) due to retinitis pigmentosa or choroideremia participated in the 5-visit wearing trial. To expand the horizontal visual field, one spectacle lens was fitted with two apex-to-apex prisms that vertically bisected the pupil on primary gaze. This provides visual field expansion at the expense of visual confusion (two objects with the same visual direction). Patients were asked to wear these spectacles as much as possible for the duration of the wearing trial (median 8, range 6-60 weeks). Clinical success (continued wear, indicating perceived overall benefit), visual field expansion, perceived direction and perceived visual ability were measured. Of 12 patients, nine chose to continue wearing the Trifield glasses at the end of the wearing trial. Of those nine patients, at long-term follow-up (35-78 weeks), three reported still wearing the Trifield glasses. Visual field expansion (median 18, range 9-38 degrees) was demonstrated for all patients. No patient demonstrated adaptation to the change in visual direction produced by the Trifield glasses (prisms). For reported difficulty with obstacles, some differences between successful and non-successful wearers were found. Trifield glasses provided reported benefits in obstacle avoidance to 7 of the 12 patients completing the wearing trial. Crowded environments were particularly difficult for most wearers. Possible reasons for long-term discontinuation and lack of adaptation to perceived direction are discussed.

Effects and feasibility of a standardised orientation and mobility training in using an identification cane for older adults with low vision: design of a randomised controlled trial

BACKGROUND

Orientation and mobility training (O&M-training) in using an identification cane, also called symbol cane, is provided to people with low vision to facilitate independent participation in the community. In The Netherlands this training is mainly practice-based because a standardised and validly evaluated O&M-training in using the identification cane is lacking. Recently a standardised O&M-training in using the identification cane was developed. This training consists of two face-to-face sessions and one telephone session during which, in addition to usual care, the client's needs regarding mobility are prioritised, and cognitive restructuring techniques, action planning and contracting are applied to facilitate the use of the cane. This paper presents the design of a randomised controlled trial aimed to evaluate this standardised O&M-training in using the identification cane in older adults with low vision.

METHODS/DESIGN

A parallel group randomised controlled trial was designed to compare the standardised O&M-training with usual care, i.e. the O&M-training commonly provided by the mobility trainer. Community-dwelling older people who ask for support at a rehabilitation centre for people with visual impairment and who are likely to receive an O&M-training in using the identification cane are included in the trial (N = 190). The primary outcomes of the effect evaluation are ADL self care and visual functioning with respect to distance activities and mobility. Secondary outcomes include quality of life, feelings of anxiety, symptoms of depression, fear of falling, and falls history. Data for the effect evaluation are collected by means of telephone interviews at baseline, and at 5 and 17 weeks after the start of the O&M-training. In addition to an effect evaluation, a process evaluation to study the feasibility of the O&M-training is carried out.

DISCUSSION

The screening procedure for eligible participants started in November 2007 and will continue until October 2009. Preliminary findings regarding the evaluation are expected in the course of 2010. If the standardised O&M-training is more effective than the current O&M-training or, in case of equal effectiveness, is considered more feasible, the training will be embedded in the Dutch national instruction for mobility trainers.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00946062.

Orientation and mobility training for adults with low vision

BACKGROUND

Orientation and mobility (O&M) training is provided to people who are visually impaired to help them maintain travel independence. It teaches them new orientation and mobility skills to compensate for reduced visual information.

OBJECTIVES

The objective of this review was to assess the effects of (O&M) training, with or without associated devices, for adults with low vision.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library, MEDLINE, SIGLE, EMBASE, National Research Register, Zetoc, LILACS, and the reference lists of articles. Updated searches were in 2006.

SELECTION CRITERIA

We planned to include randomised or quasi-randomised trials comparing (O&M) training with no training in adults with low vision.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the search results for eligibility, evaluated study quality and extracted the data.

MAIN RESULTS

Two small studies satisfied the inclusion criteria. They were consecutive phases of development of the same training curriculum and assessment tool. The intervention was administered by a volunteer on the basis of written and oral instruction. In both studies the randomisation technique was inadequate, being based on alternation, and masking was not achieved. Training had no effect in the first study while it was found to be beneficial in the second. Reasons for this may have been: the high scores obtained in the first study, suggestive of little need for training and small room for further improvement (a ceiling effect), and the refinement of the curriculum allowing better tailoring to patients' specific needs and characteristics, in the second study.

AUTHORS' CONCLUSIONS

The review found two small trials with similar methods, comparing (O&M) training to physical exercise, which were unable to demonstrate a difference. Therefore, there is little evidence on which type of orientation and mobility training is better for people with low vision who have specific characteristics and needs. Orientation and mobility instructors and scientists should plan randomised controlled studies to compare the effectiveness of different types of (O&M) training. A consensus is needed on the adoption of standard measurement instruments of mobility performance which are proved to be reliable and sensitive to the diverse mobility needs of people with low vision. For this purpose, questionnaires and performance-based tests may represent different tools that explore people with low vision's subjective experience or their objective functioning, respectively.

Feature search in persons with severe visual impairment

Feature search performance was measured in visually impaired (VI) and age-matched controls with normal vision (NV). All VI subjects were legally blind. The task was to search for a 2 degrees x 2 degrees square target among smaller 1 degrees x1 degrees distracters. Targets and distracters were white and presented on a dark background that subtended 69 degrees by 58 degrees . Three field-sizes (10 degrees , 20 degrees , and 40 degrees ) and three set sizes (8-, 16-, and 32-items) were tested. The VI subjects searched more slowly than the NV subjects, but the reaction time of both groups of subjects did not rise with increasing number of items. The latter is consistent with a parallel search. Both groups searched more slowly when field-size increased, but the VI group was affected more by the increase than the NV group.

Measurements of preferred walking speed in subjects with central and peripheral vision loss

BACKGROUND

Previous mobility studies have used Preferred Walking Speed (PWS) in order to determine the walking efficiency in terms of the Percent Preferred Walking Speed (PPWS) of visually impaired adults. PWS has been measured in previous studies using the sighted guide (SG) and non-sighted guide (NSG) techniques. This study compared the NSG, SG and string (ST) (subjects walked by holding on lightly to a cardboard tube attached to a piece of string) techniques of measuring PWS in visually impaired subjects.

METHODS

Forty visually impaired subjects with central and peripheral vision loss were recruited. PWS was measured using the NSG, SG and ST techniques. For each technique, PWS was determined by recording the time taken for a subject to walk an unobstructed, straight 20-m corridor.

RESULTS

There were no significant differences in PWS using the SG, NSG and ST techniques.

CONCLUSION

For assessing walking efficiency, either the SG, NSG or ST technique could be employed when measuring PWS in visually impaired subjects.

Evaluation of a prototype Minified Augmented-View device for patients with impaired night vision

An evaluation was carried out of the first prototype (LV-3) of a new night vision device, which incorporates visual field expansion through minification (Minified Augmented-View), to provide feedback for continuing development. Six subjects with night blindness completed visual function measurements and indoor mobility assessments without a device, with the LV-3 and with a commercially available comparison device (the Multi-Vision) at light levels representative of well lit and poorly lit streets. Device performance and potential benefits in real-world situations were evaluated at four outdoor locations (well lit to very dark). Results indicate that the see-through nature and spectacle-frame mounting of the LV-3 address some of the cosmetic and ergonomic disadvantages of currently available devices; however insufficient light sensitivity of the prototype camera limited LV-3 performance. With improved camera sensitivity and full implementation of the Minified-Contours Augmented-View concept in the next prototype, patients might be able to make better use of the novel field expansion and vision multiplexing features to aid outdoor night mobility.

Simulated Impairment of Contrast Sensitivity: Performance and Gaze Behavior during Locomotion through a Built Environment

PURPOSE

An experimental study investigated the effects of simulated impairment of contrast sensitivity (CS) on performance and eye gaze patterns during locomotion through a library.

METHOD

Normally sighted participants with simulated CS impairment (diffusive blur) walked two routes, one entailing limited change in direction (simple) and the other entailing several changes in direction (complex), while eye movements relative to the scene were recorded. Performance variables included walking speed in completing the route, pauses during travel, and collisions with objects on the route. For eye movements, dwell time and saccades were determined for each of three object classes: (1) objects on the route below eye level; (2) objects on the route extending above eye level; and (3) elsewhere-objects not on the route.

RESULTS

Walking speed was significantly affected by CS level and by route; pauses and collisions were rare. Dwell times and saccades suggested limited attention directed to low-level objects, except for CS impairment on the complex route. In the complex route, saccades and dwell times in the object class "elsewhere" were also reduced.

CONCLUSIONS

The results for the simple route suggest ballistic strategies: the participant appraises the scene and follows a more or less predetermined path. For the complex route, CS impairment appears to adversely affect information processing and locomotion. The results have implications for the design of built environments, especially with regard to the safety of visually impaired occupants during emergency scenarios.

Orientation and mobility training for adults with low vision

BACKGROUND

Orientation and mobility (O&M) training is provided to people who are visually impaired to help them maintain travel independence, teaching them new orientation and mobility skills to compensate for reduced visual information.

OBJECTIVES

The objective of this review was to assess the effects of orientation and mobility training, with or without associated devices, for adults with low vision.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials - CENTRAL (which contains the Cochrane Eyes and Vision Group trials register) (Issue 3 2002), MEDLINE (1966 to August 2002), EMBASE (1980 to September 2002) and LILACS (September 2002) and the reference lists of articles.

SELECTION CRITERIA

We planned to include randomised or quasi-randomised trials comparing orientation and mobility training with no training in adults with low vision.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the search results for eligibility.

MAIN RESULTS

No studies were found that satisfied the inclusion criteria.

REVIEWER'S CONCLUSIONS

We could not find any controlled trials on the effects of orientation and mobility training for adults with low vision. As a premise to future trials, orientation and mobility instructors and scientists should reach a consensus and develop valid measures of mobility performance which are both reliable and meaningful to people with low vision.

Vision and mobility performance of subjects with age-related macular degeneration

PURPOSE

To investigate the effects of age-related macular degeneration (ARMD) on mobility performance and to identify the vision determinants of mobility in subjects with ARMD.

METHODS

Walking speed and the number of obstacle contacts made on a 79-m indoor mobility course were measured in 21 subjects with ARMD and 11 age-matched subjects with normal vision. The mobility measures were transformed to percentage preferred walking speed and contacts score. The vision functions assessed included binocular visual acuity, contrast sensitivity, and visual field.

RESULTS

In this study, subjects with ARMD did not walk significantly slower or make significantly more obstacle contacts on the mobility course than the normally sighted subjects of similar age. Between 29% and 35% of the variance in the ARMD mobility performance was accounted for by visual field and contrast sensitivity measures. The most significant predictor of mobility performance scored as percentage preferred walking speed was the size of a binocular central scotoma.

CONCLUSION

As the size of a binocular central scotoma increases, mobility performance decreases.