Preliminary Evaluation of Two Digital Image Processing Strategies for Head-Mounted Magnification for Low Vision Patients.

PURPOSE: In an observational clinical outcome study, we tested the effectiveness and use of the combination of two innovative approaches to magnification: a virtual bioptic telescope and a virtual projection screen, implemented with digital image processing in a head-mounted display (HMD) equipped with a high-resolution video camera and head trackers. METHODS: We recruited 30 participants with best-corrected visual acuity <20/100 in the better-seeing eye and bilateral central scotomas. Participants were trained on the HMD system, then completed a 7- to 10-day in-home trial. The Activity Inventory was administered before and after the home trial to measure the effect of system use on self-reported visual function. A simulator sickness questionnaire (SSQ) and a system-use survey were administered. Rasch analysis was used to assess outcomes. RESULTS: Significant improvements were seen in functional ability measures estimated from goal difficulty ratings (Cohen's d = 0.79, P < 0.001), and reading (d = 1.28, P < 0.001) and visual information (d = 1.11, P < 0.001) tasks. There was no improvement in patient-reported visual motor function or mobility. One participant had moderately severe discomfort symptoms after SSQ item calibration. The average patient rating of the system's use was 7.14/10. CONCLUSIONS: Use of the system resulted in functional vision improvements in reading and visual information processing. Lack of improvement in mobility and visual motor function is most likely due to limited field of view, poor depth perception, and lack of binocular disparity. TRANSLATIONAL RELEVANCE: We determine if these new image processing approaches to magnification are beneficial to low vision patients performing everyday activities.

Self-reported importance and difficulty of driving in a low-vision clinic population.

PURPOSE: To validate estimates of self-perceived driving ability from difficulty ratings of driving tasks and to determine the association of the importance and difficulty of driving with the magnitude of visual impairments. METHODS: A consecutive series of 851 patients at a low-vision clinic rated the importance of driving on a four-point scale. Those who gave nonzero importance ratings then rated driving difficulty on a five-point scale. Those who gave nonzero difficulty ratings then rated the difficulty of each of 21 driving tasks on a five-point scale. Visual acuity was measured with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, and contrast sensitivity was measured with the Pelli-Robson chart. Rasch analysis was used to test the validity and reliability of self-perceived driving ability estimates from difficulty ratings of tasks. RESULTS: Patients who rated driving as not important (41%) had worse visual acuity (logMAR = 0.88) and worse contrast sensitivity (log CS = 0.83) than did those who rated driving as extremely important (55%; logMAR = 0.62; log CS =1.03; multivariate analysis of variance [MANOVA]; P = 0.003). Self-perceived driving ability correlated negatively with the overall rating of driving difficulty (r = -0.69; P < 0.001) and with logMAR (r = -0.28; P < 0.001), and correlated positively with log CS (r = 0.35; P < 0.001). The most difficult driving tasks were navigating in parking ramps, parking in the correct space, seeing lane markings, and reading signs. The least-difficult driving tasks were seeing traffic and reading the speedometer. Rasch analysis confirmed instrument validity and reliability. CONCLUSIONS: Low-vision patients appeared to devalue the goal of driving when visual impairments were more severe. Valid measures of self-perceived driving ability can be estimated from difficulty ratings of specific driving tasks.

Clinically Meaningful Rehabilitation Outcomes of Low Vision Patients Served by Outpatient Clinical Centers.

IMPORTANCE: To facilitate comparative clinical outcome research in low vision rehabilitation, we must use patient-centered measurements that reflect clinically meaningful changes in visual ability. OBJECTIVE: To quantify the effects of currently provided low vision rehabilitation (LVR) on patients who present for outpatient LVR services in the United States. DESIGN, SETTING, AND PARTICIPANTS: Prospective, observational study of new patients seeking outpatient LVR services. From April 2008 through May 2011, 779 patients from 28 clinical centers in the United States were enrolled in the Low Vision Rehabilitation Outcomes Study. The Activity Inventory, a visual function questionnaire, was administered to measure overall visual ability and visual ability in 4 functional domains (reading, mobility, visual motor function, and visual information processing) at baseline and 6 to 9 months after usual LVR care. The Geriatric Depression Scale, Telephone Interview for Cognitive Status, and Medical Outcomes Study 36-Item Short-Form Health Survey physical functioning questionnaires were also administered to measure patients' psychological, cognitive, and physical health states, respectively, and clinical findings of patients were provided by study centers. MAIN OUTCOMES AND MEASURES: Mean changes in the study population and minimum clinically important differences in the individual in overall visual ability and in visual ability in 4 functional domains as measured by the Activity Inventory. RESULTS: Baseline and post-rehabilitation measures were obtained for 468 patients. Minimum clinically important differences (95% CIs) were observed in nearly half (47% [95% CI, 44%-50%]) of patients in overall visual ability. The prevalence rates of patients with minimum clinically important differences in visual ability in functional domains were reading (44% [95% CI, 42%-48%]), visual motor function (38% [95% CI, 36%-42%]), visual information processing (33% [95% CI, 31%-37%]), and mobility (27% [95% CI, 25%-31%]). The largest average effect size (Cohen d = 0.87) for the population was observed in overall visual ability. Age (P = .006) was an independent predictor of changes in overall visual ability, and logMAR visual acuity (P = .002) was predictive of changes in visual information processing. CONCLUSIONS AND RELEVANCE: Forty-four to fifty percent of patients presenting for outpatient LVR show clinically meaningful differences in overall visual ability after LVR, and the average effect sizes in overall visual ability are large, close to 1 SD.

Visual ability of patients seeking outpatient low vision services in the United States.

IMPORTANCE: Most patients with low vision are elderly and have functional limitations from other health problems that could add to the functional limitations caused by their visual impairments. OBJECTIVE: To identify factors that contribute to visual ability measures in patients who present for outpatient low vision rehabilitation (LVR) services. DESIGN, SETTING, AND PARTICIPANTS: As part of a prospective, observational study of new patients seeking outpatient LVR, 779 patients from 28 clinical centers in the United States were enrolled in the Low Vision Rehabilitation Outcomes Study (LVROS) from April 25, 2008, through May 2, 2011. The Activity Inventory (AI), an adaptive visual function questionnaire, was administered to measure overall visual ability and visual ability in 4 functional domains (reading, mobility, visual motor function, and visual information processing) at baseline before LVR. The Geriatric Depression Scale, Telephone Interview for Cognitive Status, and Medical Outcomes Study 36-Item Short-Form Health Survey physical functioning questionnaires were also administered to measure patients' psychological, cognitive, and physical health states, respectively. MAIN OUTCOMES AND MEASURES: Predictors of visual ability and functional domains as measured by the AI. RESULTS: Among the 779 patients in the LVROS sample, the mean age was 76.4 years, 33% were male, and the median logMAR visual acuity score was 0.60 (0.40-0.90 interquartile range). Correlations were observed between logMAR visual acuity and baseline visual ability overall (r = -0.42) and for all functional domains. Visual acuity was the strongest predictor of visual ability (P < .001) and reading ability (P < .001) and had a significant independent effect on the other functional domains. Physical ability was independently associated with (P < .001) overall visual ability as well as mobility and visual motor function. Depression had a consistent independent effect (P < .001) on overall visual ability and on all functional domains, whereas cognition had an effect on only reading and mobility (P < .001). CONCLUSIONS AND RELEVANCE: Visual ability is a multidimensional construct, with visual acuity, depression, physical ability, and cognition explaining more than one-third of the variance in visual ability as measured by the AI. The significant contributions of the nonvisual factors to visual ability measures and the rehabilitation potential (ie, ceiling) effects they may impose on LVR are important considerations when measuring baseline visual ability and ultimately LVR outcomes in ongoing clinical research.

Baseline traits of low vision patients served by private outpatient clinical centers in the United States.

OBJECTIVE: To characterize the traits of low vision patients who seek outpatient low vision rehabilitation (LVR) services in the United States. METHODS: In a prospective observational study, we enrolled 764 new low vision patients seeking outpatient LVR services from 28 clinical centers in the United States. Before their initial appointment, multiple questionnaires assessing daily living and vision, physical, psychological, and cognitive health states were administered by telephone. Baseline clinical visual impairment measures and disorder diagnoses were recorded. RESULTS: Patients had a median age of 77 years, were primarily female (66%), and had macular disease (55%), most of which was nonneovascular age-related macular degeneration. More than one-third of the patients (37%) had mild vision impairment with habitual visual acuity (VA) of 20/60 or greater. The VA correlated well with contrast sensitivity (r = -0.52) but poorly with self-reported vision quality. The intake survey revealed self-reported physical health limitations, including decreased endurance (68%) and mobility problems (52%). Many patients reported increased levels of frustration (42%) and depressed mood (22%); memory and cognitive impairment (11%) were less frequently endorsed. Patients relied on others for daily living support (87%), but many (31%) still drove. CONCLUSIONS: Most patients seeking LVR are geriatric and have macular disease with relatively preserved VA. The disparity between VA and subjective quality of vision suggests that LVR referrals are based on symptoms rather than on VA alone. Patients seen for LVR services have significant physical, psychological, and cognitive disorders that can amplify vision disabilities and decrease rehabilitation potential.

The Activity Inventory: an adaptive visual function questionnaire.

PURPOSE: The Activity Inventory (AI) is an adaptive visual function questionnaire that consists of 459 Tasks nested under 50 Goals that in turn are nested under three Objectives. Visually impaired patients are asked to rate the importance of each Goal, the difficulty of Goals that have at least some importance, and the difficulty of Tasks that serve Goals that have both some importance and some difficulty. Consequently, each patient responds to an individually tailored set of questions that provides both a functional history and the data needed to estimate the patient's visual ability. The purpose of the present article is to test the hypothesis that all combinations of items in the AI, and by extension all visual function questionnaires, measure the same visual ability variable. METHODS: The AI was administered to 1880 consecutively-recruited low vision patients before their first visit to the low vision rehabilitation service. Of this group, 407 were also administered two other visual function questionnaires randomly chosen from among the Activities of Daily Living Scale (ADVS), National Eye Institute Visual Functioning Questionnaire (NEI VFQ), 14-item Visual Functioning Index (VF-14), and Visual Activities Questionnaire (VAQ). Rasch analyses were performed on the responses to each VFQ, on all responses to the AI, and on responses to various subsets of items from the AI. RESULTS: The pattern of fit statistics for AI item and person measures suggested that the estimated visual ability variable is not unidimensional. Reading-related and other items requiring high visual resolution had smaller residual errors than expected and mobility-related items had larger residual errors than expected. The pattern of person measure residual errors could not be explained by the disorder diagnosis. When items were grouped into subsets representing four visual function domains (reading, mobility, visual motor, visual information), and separate person measures were estimated for each domain as well as for all items combined, visual ability was observed to be equivalent to the first principal component and accounted for 79% of the variance. However, confirmatory factor analysis showed that visual ability is a composite variable with at least two factors: one upon which mobility loads most heavily and the other upon which reading loads most heavily. These two factors can account for the pattern of residual errors. High product moment and intraclass correlations were observed when comparing different subsets of items within the AI and when comparing different VFQs. CONCLUSIONS: Visual ability is a composite variable with two factors; one most heavily influences reading function and the other most heavily influences mobility function. Subsets of items within the AI and different VFQs all measure the same visual ability variable.

Rehabilitation of hospital inpatients with visual impairments and disabilities from systemic illness.

OBJECTIVES: To describe the comorbidity of visual impairment and disability among patients hospitalized for systemic illness and to discuss rehabilitation. DESIGN: Retrospective study. SETTING: Hospital-based, academic tertiary medical center with referring neurology, ophthalmology, and rehabilitation units. PARTICIPANTS: Ninety-three hospitalized patients referred to the low vision rehabilitation clinic primarily by the physical medicine and rehabilitation and neurology units. INTERVENTIONS: Measurements of best-corrected visual acuity and other visual function testing. Referrals were made for prescriptive glasses, assistive devices, rehabilitation, resources, and ophthalmologic evaluation. MAIN OUTCOME MEASURES: Specialized services, presence of comorbidities, and visual function measurements. RESULTS: The mean admitting visual acuity revealed a moderate visual impairment. The primary diagnosis for admission (51%) was cerebrovascular accidents. There was a mean of 3.5 other comorbidities. CONCLUSIONS: The majority of patients admitted to the hospital for systemic diseases also had visual impairments. In many patients, this visual disability (either from the systemic and/or ocular disease) interfered with their activities of daily living.

Visual disability variables. I: the importance and difficulty of activity goals for a sample of low-vision patients.

OBJECTIVE: To test the validity and reliability of latent trait measures estimated from ratings by low-vision patients of the importance and difficulty of selected activity goals. DESIGN: Validation of a telephone-administered functional assessment instrument using Rasch analysis of self-assessment ratings. SETTING: Telephone interviews of respondents in their homes. Participants Consecutive series of 600 outpatients with low vision. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Ratings of the importance and difficulty of achieving 41 activity goals. Person and item traits were measured with the Andrich rating scale model. Measurement validity and reliability were tested statistically by comparing response patterns and distributions with measurement model expectations. RESULTS: Patients could distinguish only 3 categories of importance and 4 categories of difficulty. The distributions of person and item measure fit statistics were consistent with 2 unidimensional constructs: value of independence estimated from importance ratings and visual ability estimated from difficulty ratings. However, 8 of 41 activity goals were poor estimators of value of independence and 7 of 41 activity goals were poor estimators of visual ability. Person measure distributions could be divided into 3 statistically distinct strata for estimates from both importance ratings and difficulty ratings. Item measure distributions could be divided into 21 strata for estimates from importance ratings and 7 strata for estimates from difficulty ratings. CONCLUSIONS: The 2 variables that define visual disability-value of independence and visual ability-are valid constructs that can be estimated accurately and reliably from patient ratings of the importance and difficulty of activity goals.

Visual disability variables. II: The difficulty of tasks for a sample of low-vision patients.

OBJECTIVES: To test the validity and reliability of measures of visual ability and to evaluate the relation between measurements made at the task level and measurements made at the goal level of a hierarchical model for visual disability. DESIGN: Validation of a telephone-administered functional assessment instrument using Rasch analysis on self-assessment ratings. SETTING: Telephone interviews of respondents in their homes. PARTICIPANTS: Consecutive series of 600 outpatients with low vision. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Ordinal ratings of the difficulty in performing a subset of 337 tasks. Measures of the visual ability of each patient and the required visual ability to perform each task were made using the Andrich rating scale model. Measurement validity and reliability were tested statistically by comparing response patterns and distributions to measurement model expectations. RESULTS: Results were consistent with a single visual ability construct. Patients' visual ability estimated from task difficulty ratings agreed with estimates from goal difficulty ratings ( r =.74); the difficulty of individual goals was equal to the weighted average of the difficulties of subsidiary tasks ( r =.79). However, conclusions from the Rasch analysis were not confirmed by principal components analysis of item residuals, which indicated that visual ability had a 2-dimensional structure, with 1 factor related to mobility and the other related to reading. Factor analysis on person measures estimated from subsets of functionally grouped items confirmed the 2-dimensional structure of visual ability. CONCLUSIONS: Our study results confirm the hierarchical structure of the Activity Breakdown Structure model and show how the individualized Activity Inventory can produce measures of limitations in functional vision.