Kinematic analysis of step ascent among patients with central visual field loss.

Vision is of paramount importance in regulating adaptive gait. Using three-dimensional motion analysis, the current study investigated how central visual field loss (CFL) affects step ascent. Ten patients with chronic CFL (77 ± 10 years) and 13 visual normal participants (72 ± 6 years) walked up to and ascended a single step (of varying height). Movement kinematics assessed the period immediately prior to and during step ascent. Compared to visual normal participants, patients with CFL exhibited a lower lead foot horizontal crossing velocity, increased lead limb swing time and increased head flexion (looking down at more immediate areas of the ground/step). They also took longer to initiate the step up, transfer weight to the lead foot upon landing on the upper level and increased trail limb swing time when negotiating the medium and high step height. Increased variability was also shown in a number of dependent measures. Data indicate that during step ascent, patients with CFL exhibit a cautious stepping strategy when compared to visual normal participants. This cautious strategy becomes increasingly evident when negotiating higher step heights, as shown by an increased planning time prior to entering the relatively unstable period of single support during the step up. The increased variability among CFL patients increases their likelihood of experiencing dynamic instability and falling during step ascent.

Adjustment to vision loss in a mixed sample of adults with established visual impairment.

PURPOSE: To determine factors associated with the level of adjustment to vision loss in a cross-sectional sample of adults with mixed visual impairment. METHODS: One hundred participants were administered the Acceptance and Self-Worth Adjustment Scale (AS-WAS) to assess adjustment to vision loss. The severity of vision loss was determined using binocular clinical visual function assessments including visual acuity, contrast sensitivity, reading performance, and visual fields. Key demographics including age, duration of visual impairment, general health, education, and living arrangements were evaluated, as were self-reported vision-related activity limitation (VRAL), depression, social support, and personality. RESULTS: Multivariate analysis showed that higher levels of depressive symptoms (ß = -0.26, P < 0.01) and of the personality trait neuroticism (ß = -0.33, P < 0.001), and lower levels of the personality trait of conscientiousness (ß = 0.29, P < 0.01), were associated with poorer adjustment to vision loss, explaining 56% variance. CONCLUSIONS: Adjustment to vision loss is significantly associated with depression and certain traits of personality (specifically neuroticism and conscientiousness), independent of the severity of vision loss, VRAL, and duration of vision loss. The results suggest certain individuals may be predisposed to exhibiting less adjustment to vision loss due to personality characteristics, and exhibit poorer adjustment owing to or as a consequence of depression, rather than due to other factors such as the onset and severity of visual impairment.

Guidelines for predicting performance with low vision AIDS.

PURPOSE: To determine predictors of success in reading with low vision aids, in terms of reading acuity, optimum acuity reserve, and maximum reading speed, for observers with vision loss from various causes. METHODS: One hundred people with vision loss affecting their daily lives participated. Clinical visual function measurements of distance acuity, contrast sensitivity, binocular threshold visual fields, and near reading performance with a MNRead chart at 40 cm were obtained. Reading performance aided by habitual low vision aids was also assessed with a MNRead chart. RESULTS: Aided reading acuity was best predicted by clinical reading acuity and contrast sensitivity. For most observers, a 2:1 acuity reserve was sufficient to achieve near-maximum reading speed, but one-third of observers with aided reading acuity better than 1.2 M required a higher acuity reserve. Aided maximum reading speed was best predicted by clinically assessed reading speed and by clinical reading acuity. CONCLUSIONS: People with vision impairment are likely to achieve 1 M with a low vision aid if their clinically assessed reading acuity is better than 0.85 logMAR. If acuity is worse than this, but contrast sensitivity is better than 1.05 logCS, 1M is also likely to be achieved. A 2:1 acuity reserve is adequate for 75% of observers, but those with good aided reading acuity may require further magnification to achieve best reading speeds. Fluent reading (>80 words per minute) is likely to be achieved if an observer reads fluently with large print at a fixed working distance and if clinically assessed reading acuity is better than 1.0 logMAR.

Important areas of the central binocular visual field for daily functioning in the visually impaired.

PURPOSE: To determine the areas of the central binocular visual field which correspond best with self-reported vision related activity limitations (VRAL) in individuals with visual impairment using a clinically relevant and accessible technique. METHODS: One hundred participants with mixed visual impairment undertook binocular threshold visual field testing using a Humphrey 30-2 SITA Fast program. The Activity Inventory (AI) was administered to assess overall, mobility related and reading related self-reported VRAL as part of a face-to-face clinical interview. Different eccentricities of the binocular field (central 5, 5-10, and 10-30°) were compared to self-reported VRAL in bivariate analyses and further explored using multivariate analyses. RESULTS: All areas of the binocular visual field were significantly associated with self-reported VRAL in bivariate analyses, with greater field loss associated with increased VRAL (p < 0.001). Multivariate analyses identified that function of the central 5-10° best predicted overall self-reported VRAL, and function of the central 5° (especially the right-hand-side) and the central 10-30° (especially 10-20°) best predicted self-reported VRAL in reading and mobility tasks, respectively. CONCLUSIONS: The results highlight the association between central binocular visual fields and self-reported VRAL in people with visual impairment. Central binocular fields can be measured using a widely available threshold test in order to understand the likely functional limitations of those with vision loss, particularly in mobility tasks. Self-reported VRAL can be estimated using the regression equations and graphs provided and difficulty levels in specific tasks can be determined.

Factors influencing self-reported vision-related activity limitation in the visually impaired.

PURPOSE: The use of patient-reported outcome (PRO) measures to assess self-reported difficulty in visual activities is common in patients with impaired vision. This study determines the visual and psychosocial factors influencing patients' responses to self-report measures, to aid in understanding what is being measured. METHODS: One hundred visually impaired participants completed the Activity Inventory (AI), which assesses self-reported, vision-related activity limitation (VRAL) in the task domains of reading, mobility, visual information, and visual motor tasks. Participants also completed clinical tests of visual function (distance visual acuity and near reading performance both with and without low vision aids [LVAs], contrast sensitivity, visual fields, and depth discrimination), and questionnaires assessing depressive symptoms, social support, adjustment to visual loss, and personality. RESULTS: Multiple regression analyses identified that an acuity measure (distance or near), and, to a lesser extent, near reading performance without LVAs, visual fields, and contrast sensitivity best explained self-reported VRAL (28%-50% variance explained). Significant psychosocial correlates were depression and adjustment, explaining an additional 6% to 19% unique variance. Dependent on task domain, the parameters assessed explained 59% to 71% of the variance in self-reported VRAL. CONCLUSIONS: Visual function, most notably acuity without LVAs, is the best predictor of self-reported VRAL assessed by the AI. Depression and adjustment to visual loss also significantly influence self-reported VRAL, largely independent of the severity of visual loss and most notably in the less vision-specific tasks. The results suggest that rehabilitation strategies addressing depression and adjustment could improve perceived visual disability.

Derivation of the acceptance and self-worth adjustment scale.

PURPOSE: The original 55-item Nottingham Adjustment Scale (NAS) is a first generation self-report instrument constructed using classical test theory to evaluate adjustment to vision loss. This study assesses the function of the NAS using Rasch analysis in a sample of adults with visual impairment and presents a revised second-generation instrument. METHODS: Ninety-nine subjects with established vision loss (median onset 5 years) were administered the NAS. Rasch analysis was performed to: (1) determine optimum response scale function, (2) aid item reduction, (3) determine reliability indices and item targeting, (4) assess unidimensionality using Rasch-based principal component analysis, (5) assess differential item functioning (notable defined as >1.0 logit), and (6) formulate person measures to correlate with Geriatric Depression Scale scores and distance visual acuity to indicate convergent and discriminant validity, respectively. RESULTS: Response categories exhibited underutilization, which when repaired improved response scale functioning and ordered structural calibrations. Misfitting items were removed iteratively until all items had mean-square infit and outfit values of 0.70 to 1.30. However, principal component analysis confirmed insufficient unidimensionality (two contrasts identified, eigenvalues 2.4 and 2.3). Removal of these contrasts and two further iterations restored unidimensionality. Despite item mistargeting (1.58 logits), the revised 19-item instrument demonstrated good person (0.85) and item (0.96) reliability coefficients, good convergent and discriminant validity, and no systematic differential item functioning. The resultant 19-item instrument was termed the Acceptance and Self-Worth Adjustment Scale (AS-WAS). CONCLUSIONS: In those with established vision loss, the 19-item Acceptance and Self-Worth Adjustment Scale is a reliable and valid instrument that estimates the level of adjustment concerned with acceptance, attitudes, self-esteem, self-efficacy, and locus of control. An additional measure of depression and anxiety is recommended to assess adjustment in a broader sense. Confirmation of item ordering is required if to be used in those with newly acquired vision loss.