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Importance Randomized clinical trials are needed to compare effectiveness and cost-effectiveness of different low-vision (LV) programs. Objective To determine the value of adding LV rehabilitation with a therapist compared with LV services without intervention. Design, Setting, and Participants A randomized clinical trial was conducted from September 27, 2010, to July 31, 2014, of 323 veterans with macular diseases and best-corrected distance visual acuity (BCDVAbetter-eye) of 20/50 to 20/200. Masked interviewers administered questionnaires by telephone before and after LV treatment. Using an intention-to-treat design, participants were randomized to receive LV devices with no therapy or LV devices with a rehabilitation therapist providing instruction and homework on the use of LV devices, eccentric viewing, and environmental modification. Visual ability was measured in dimensionless log odds units (logits) (0.14-logit change in visual ability corresponds to ability change expected from a 1-line change in visual acuity). Interventions Low-vision devices without therapy and LV devices with therapy. Main Outcomes and Measures Comparison of changes (baseline to 4 months) in overall visual ability and in 4 functional domains (reading, visual information, visual motor, and mobility) estimated from responses to the Veterans Affairs Low Vision Visual Functioning Questionnaire (higher scores indicates more ability or less difficulty in performing activities), and comparison of MNREAD changes (baseline to end of treatment) in maximum reading speed, critical print size, and reading acuity (higher number indicates lower visual acuity). Results Of the 323 participants, 314 were male (97.2%); mean (SD) age, 80 (10.5) years. Basic LV was effective in improving visual ability. However, the LV rehabilitation group improved more in all visual function domains except mobility. Differences were 0.34-logit reading (95% CI, 0.0005 to 0.69; P = .05), 0.27-logit visual information (95% CI, 0.01 to 0.53; P = .04), 0.37-logit visual motor (95% CI, 0.08 to 0.66; P = .01), and 0.27-logit overall (95% CI, 0.06 to 0.49; P = .01). For MNREAD measures, there was more improvement in reading acuity (difference, −0.11 logMAR, 95% CI, −0.15 to −0.07; P P = .005), but not critical print size for the LV rehabilitation group (−0.06 logMAR; 95% CI, −0.12 to 0.002; P = .06). In stratified analyses, the LV rehabilitation group with BCDVAbetter-eye worse than 20/63 to 20/200 improved more in visual ability (reading, visual motor, and overall). Differences were 0.56-logit reading ability (95% CI, 0.08-1.04; P = .02), 0.40-logit visual motor (95% CI, 0.03-0.78; P = .04), 0.34-logit overall (95% CI, 0.06-0.62; P = .02). There was no significant difference between treatment groups for those with BCDVAbetter-eye of 20/50 to 20/63. Conclusions and Relevance Both basic LV alone and combined with LV rehabilitation were effective, but the added LV rehabilitation increased the effect only for patients with BCDVAbetter-eye worse than 20/63 to 20/200. Basic LV services may be sufficient for most LV patients with mild visual impairment. Trial Registration clinicaltrials.gov Identifier:NCT00958360

We evaluated the impact of glaucoma-related vision loss on reading ability and reading engagement in 10 reading activities.A total of 63 glaucoma patients and 59 glaucoma suspect controls self-rated their level of reading difficulty for 10 reading items, and responses were analyzed using Rasch analysis to determine reading ability. Reading engagement was assessed by asking subjects to report the number of days per week they engaged in each reading activity. Reading restriction was determined as a decrement in engagement.Glaucoma subjects more often described greater reading difficulty than controls for all tasks except puzzles (P0.05). The most difficult reading tasks involved puzzles, books, and finances, while the least difficult reading tasks involved notes, bills, and mail. In multivariable weighted least squares regression models of Rasch-estimated person measures of reading ability, less reading ability was found for glaucoma patients compared to controls (β = -1.60 logits, P0.001). Among glaucoma patients, less reading ability was associated with more severe visual field (VF) loss (β = -0.68 logits per 5-dB decrement in better-eye VF mean deviation [MD], P0.001) and contrast sensitivity (β = -0.76 logits per 0.1-unit lower log CS, P0.001). Each 5-dB decrement in the better-eye VF MD was associated with book reading on 18% fewer days (P = 0.003) and newspaper reading on 10% fewer days (P = 0.008). No statistically significant reading restriction was observed for other reading activities (P0.05).Glaucoma patients have less reading ability and engage less in a variety of different reading activities, particularly those requiring sustained reading. Future work should evaluate the mechanisms underlying reading disability in glaucoma to determine how patients can maintain reading ability and engagement.

PURPOSE: To characterize functional complaints of new low-vision rehabilitation patients. DESIGN: Prospective observational study. PARTICIPANTS: The Low Vision Rehabilitation Outcomes Study recruited 819 patients between 2008 and 2011 from 28 clinical centers in the United States. METHODS: New patients referred for low-vision rehabilitation were asked, “What are your chief complaints about your vision?” before their appointment. Full patient statements were transcribed as free text. Two methods assessed whether statements indicated difficulty in each of 13 functional categories: (1) assessment by 2 masked clinicians reading the statement, and (2) a computerized search of the text for specific words or word fragments. Logistic regression models were used to predict the influence of age, gender, and visual acuity on the likelihood of reporting a complaint in each functional category. MAIN OUTCOME MEASURES: Prevalence and risk factors for patient concerns within various functional categories. RESULTS: Reading was the most common functional complaint (66.4% of patients). Other functional difficulties expressed by at least 10% of patients included driving (27.8%), using visual assistive equipment (17.5%), mobility (16.3%), performing in-home activities (15.1%), lighting and glare (11.7%), and facial recognition and social interactions (10.3%). Good agreement was noted between the masked clinician graders and the computerized algorithm for categorization of functional complaints (median κ of 0.84 across the 13 categories). Multivariate logistic regression models demonstrated that the likelihood of reading difficulties increased mildly with age (odds ratio, 1.4 per 10-year increment in age; 95% confidence interval, 1.3–1.6), but did not differ with visual acuity (P = 0.09). Additionally, men were more likely to report driving difficulties and difficulties related to lighting, whereas women were more likely to report difficulty with either in-home activities or facial recognition or social interaction (P

With increased emphasis on functional outcomes in ophthalmology, third-party health care payers and research funding agencies have turned their attention to the development and use of visual function questionnaires. Since 1980, more than a dozen such self-report visual function questionnaires have been developed. All of these instruments include items that ask about specific daily activities; patients must respond with a rating that represents the level of difficulty that they experience with the activity described. This article reviews all of the known instruments, with special attention paid to their validity and reliability. Most validation studies have reported high response consistency across items and significant correlations of instrument scores with visual impairment measures. Only two studies have measured test-retest reliability. The developers of visual function questionnaires typically divide the items into several different subscales, suggesting that different variables are being measured. Although the items are very similar for the different instruments, there is little agreement among instruments on the definition of subscales. All instruments are scored as the average of the ordinal patient ratings across items for each subscale and/or for the total instrument. Measurement issues underlying the scoring of ordinal patient ratings are discussed. It is argued that unless the instruments can be converted to interval scales, the averaging of patient ratings does not yield true measurements. The three visual function questionnaires that were calibrated with a statistical item response model, which estimates interval scales, are reviewed. It is concluded that future research and development should devote additional attention to the measurement properties of functional assessment instruments.

The National Eye Institute developed a visual functioning questionnaire (NEI-VFQ) designed to assess health-related quality of life of patients with visual impairments. The developers of the NEI-VFQ distributed the original 52 items into 13 different domains. The recommended method for scoring the NEI-VFQ is to linearly transform the sum of the ordinal ratings to each item within each domain to produce 13 scores. The major shortcoming of this scoring method is that sums of ordinal numbers do not necessarily generate valid measurement scales. However, Rasch models can be used to estimate interval measurement scales from ordinal responses to items. We administered 27 items from the 52-item NEI-VFQ to 341 patients with low vision. Rasch analysis was used to estimate the ‘visual ability’ required by each item for a particular response (item measures) and to estimate the ‘visual ability’ of each patient (person measures). The validity of the model was evaluated by examining the distributions of residuals for item and person measures. We observed that the 17 items we tested from the NEI-VFQ that require difficulty ratings produce a valid interval scale for low-vision patients. The estimated person measures of visual ability are linear with log MAR acuity. The ten items that require frequency or level of agreement ratings do not work together to produce a valid interval scale. Rather, these items appear to be confounded by other variables distributed in the patient sample (e.g. psychological state). The visual ability scale estimated from the 17 NEI-VFQ items is proportional to the visual ability scales estimated from two earlier studies that also elicited difficulty ratings from low-vision patients.

The aim of this study was to test the hypothesis that an extra-retinal signal combines with retinal velocity in a linear manner as described by existing models to determine perceived velocity. To do so, we utilized a method that allowed the determination of the relative contributions of the retinal-velocity and the extra-retinal signals for the perception of stimulus velocity. We determined the velocity (speed and direction) of a stimulus viewed with stationary eyes that was perceptually the same as the velocity of the stimulus viewed with moving eyes. Eye movements were governed by the tracking (or pursuit) of a separate pursuit target. The velocity-matching data were unable to be fit with a model that linearly combined a retinal-velocity signal and an extra-retinal signal. A model that was successful in explaining the data was one that takes the difference between two simple saturating non-linear functions, g and f, each symmetric about the origin, but one having an interaction term. That is, the function g has two arguments: retinal velocity, Ṙ, and eye velocity, Ė. The only argument to f is retinal velocity, Ṙ. Each argument has a scaling parameter. A comparison of the goodness of fits between models demonstrated that the success of the model is the interaction term, i.e. the modification of the compensating eye velocity signal by the retinal velocity prior to combination.

In this study, the authors measured the print sizes in 10 sections of over 100 U.S. newspapers and found that within a newspaper, the print sizes among sections may vary by more than a factor of 2 and that among newspapers, the print size of a single section may vary by a factor of more than 1.5. These findings challenge the assumption that newspapers use a standard print size and thus that persons with low vision can read all newspapers with magnifiers that are appropriate for reading 1 M print (1.45mm). The authors also give guidelines for low vision specialists in recommending magnification.

This article presents a theoretical interpretation of patient-reported outcomes of low-vision rehabilitation (LVR) using rating scale questionnaires and uses previously published results of LVR outcome studies to illustrate theoretical points and validate assumptions.Patients' judgments of the difficulty they have performing tasks are interpreted as magnitude estimates of their functional reserve for each task, which is the difference between their visual ability and the visual ability demanded by the task. We assume that improvements in functional reserve can occur by increasing the patient's visual ability with medical, surgical, or refractive interventions or decreasing the visual ability demanded by the item with activity-specific vision assistive equipment, adaptations, and environmental modifications. Activity-specific interventions cause differential item functioning (intervention-related DIF). Intervention-related DIF makes the measured size of the treatment effect dependent on the item content and the mix of responsive and unresponsive items to intervention.Because intervention-related DIF depends on the choice of items, the outcome measure selected should be appropriate to the aims of the intervention and the impairment level of the sample to demonstrate the full effects of an intervention. Items that are given extreme positive ratings at preintervention baseline (e.g., "not difficult") have no room for improvement. These items must also be filtered out because they will dilute the measured effect of the activity-specific interventions of LVR.

Ophthalmology and the ageing society / , Ophthalmology and the ageing society / , کتابخانه دیجیتال جندی شاپور اهواز

Guest Editorial: Patient-reported measurements have become standard outcomes alongside vision tests in clinical trials; at times, even being the main outcome measure. With a developing research focus, these instruments are evolving from relatively simple measures to increasingly discriminatory, reliable, and valid ones. This feature issue of Optometry and Vision Science showcases the latest research from this broad field. Contributions include reviews of existing patient-reported outcome measures (PROMs), testing or application of PROMs, testing or use of health valuation instruments, and qualitative research into the patient’s perspective of eye and vision problems or treatments. Refereed/Peer-reviewed

When visual system disorders result in bilateral visual impairments, patients have difficulty performing their customary activities and experience a diminished quality of life (West et al. 2002). Visual impairments increase patients’ risk of falling (Ivers et al. 1998), injury (Salive et al. 1994), poor general health (Crews and Campbell 2001), depression (Casten et al. 2004), and even death (Pedula et al. 2006). Activity-limiting chronic visual impairments, collectively called “low vision,” most often are caused by age-related visual system disorders, with age-related macular degeneration, glaucoma, diabetic retinopathy, and cataract leading the list (Congdon et al. 2004). Some visual system disorders, such as diabetic retinopathy, are manifestations of more general disorders that frequently produce co-disabilities. But most low vision patients are elderly, so comorbidities and co-disabilities from diseases unrelated to their visual system disorders are common (Ahmadian and Massof 2008). Thus, for a large portion of the low vision population, activity limitations from visual impairments are superimposed on and worsen activity limitations from comorbidities (Langelaan et al. 2009).

A balance scale metaphor is offered as a tool for explaining the principles of measurement and for visualizing the internal structure of dichotomous and polytomous Rasch models. The balance scale metaphor is used to guide the derivation of a general polytomous Rasch model and to illustrate the additional assumptions subsequently required to derive the Andrich (1978) rating scale model (RSM) and the Masters (1982) partial credit model (PCM). The metaphor is used to present the argument that the RSM conforms to the rules of measurement, but the PCM has interactions implicit in its structure that violate specific objectivity and sufficiency of raw scores, which challenge its status as a Rasch model. Using the metaphor and a literal interpretation of the narrative description of the PCM by Masters (1982), a new version of the PCM is derived that does conform to the rules of measurement.

To compare the efficacy of problem-solving therapy (PST) with supportive therapy (ST) to improve targeted vision function (TVF) in age-related macular degeneration (AMD).Single-masked, attention-controlled, randomized clinical trial with outcome assessments at 3 months (main trial endpoint) and 6 months (maintenance effects).Patients with AMD (n = 241) attending retina practices.Whereas PST uses a structured problem-solving approach to reduce vision-related task difficulty, ST is a standardized attention-control treatment.We assessed TVF, the 25-item National Eye Institute Vision Function Questionnaire plus Supplement (NEI VFQ), the Activities Inventory (AI), and vision-related quality of life (QoL).There were no between-group differences in TVF scores at 3 (P = 0.47) or 6 (P = 0.62) months. For PST subjects, mean ± standard deviation TVF scores improved from 2.71±0.52 at baseline to 2.18±0.88 at 3 months (P = 0.001) and were 2.18±0.95 at 6 months (change from 3 to 6 months, P = 0.74). For ST subjects, TVF scores improved from 2.73±0.52 at baseline to 2.14±0.96 at 3 months (P = 0.001) and were 2.15±0.96 at 6 months (change from 3 to 6 months, P = 0.85). Similar proportions of PST and ST subjects had less difficulty performing a TVF goal at 3 months (77.4% vs 78.6%, respectively; P = 0.83) and 6 months (76.2% vs 79.1%, respectively; P = 0.61). There were no changes in the NEI VFQ or AI. Vision-related QoL improved for PST relative to ST subjects at 3 months (F(4, 192) = 2.46; P = 0.05) and at 6 months (F(4, 178) = 2.55; P = 0.05). The PST subjects also developed more adaptive coping strategies than ST subjects.We found that PST was not superior to ST at improving vision function in patients with AMD, but that PST improved their vision-related QoL. Despite the benefits of anti-vascular endothelial growth factor treatments, AMD remains associated with disability, depression, and diminished QoL. This clinical reality necessitates new rehabilitative interventions to improve the vision function and QoL of older persons with AMD.The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Crossing the street is an important but risky activity of daily living. If a pedestrian makes a poor street-crossing decision, the consequence could be serious injury or death. In order to advance our understanding of how visual and auditory information is sampled and processed to make street-crossing decisions, an accurate, reliable, and sensitive psychophysical and/or psychometric method of measurement of the street-crossing decision variable must first be developed and validated. The aim of this paper is to develop and validate a new metric for this variable.Using a 5 point rating scale, safety ratings for eight different vehicular gap times of different durations were recorded along an unsignalized, two-lane street of one-way traffic. Safety ratings were collected from 12 normally sighted and 10 visually impaired subjects. Receiver Operating Characteristic (ROC) curves were estimated for all possible gap pairs and the discriminability (d') of the street-crossing decision variable for all gap pairs was estimated from the area under the ROC curve.We found that our data conform with the assumptions that the underlying distributions of the decision variable are continuous, monotonic and unbounded. Using the dissimilarity matrix of d' values for each person (which were computed for all pairings of gap times) in a one-dimensional scaling model, we estimated the means of each distribution of the decision variable relative to a center of gravity (COG) for the person. When plotting the means of the distributions against vehicular gap time, the data are best described as a non-linear function symmetric about the COG. We showed that the x-intercept (t(COG)) and slope from the non-linear function can be used to assess a person's street-crossing decision-making performance for different amounts of sensory information. Using our newly developed metrics, we found no significant difference in t(COG) (p=0.30) and in the slopes of the model (p=0.85) between normally sighted and visually impaired subjects. In addition, both subject groups centered their t(COG) close to their actual crossing time.A newly developed model for measuring a street-crossing decision variable functions as a valid metric that can be used to quantify street-crossing decision-making performance in pedestrians. Using this new metric, we observed that visually impaired subjects who travel independently are able to make street-crossing judgments that are comparable to those of normally sighted subjects.

Background: Modern psychometric theory is now routinely used in clinical vision research, as well as other areas of health research, to measure latent health states on continuous interval scales from responses to self-report rating scale questionnaires. Two competing theories are commonly employed: Rasch theory and item response theory.Methods: Because the field is currently in transition from using traditional scoring algorithms based on classical test theory to using the more modern approaches, this article offers a tutorial review of Rasch theory and item response theory and of the analytical methods employed by the two theories to estimate and validate measures.

To develop and validate a patient-reported outcome measure of refractive error for persons living in developing countries.A 21-item visual function questionnaire was developed from existing instruments through pilot testing in 51 urban Indian adults with refractive error. This was then administered to 400 adults aged 18 to 45 in Delhi, India. Rasch analysis was performed to determine item fit, differential item functioning (DIF), targeting of the instrument to the study population, and instrument precision.The removal of 5 items from the instrument resulted in better fit to the Rasch model. Reducing the number of possible responses from five to four further improved fit. Analysis of the person-item map including the Fisher information function demonstrated acceptable targeting of the instrument to this population. The person separation index was good (2.03), demonstrating ability to differentiate between 3 strata of respondents.Revisions to existing instruments to measure visual function in persons with refractive error resulted in an instrument that conformed to the Rasch model. Identifying activities that are more difficult to perform with refractive error in this setting might further improve the instrument. The 16-item instrument was able to differentiate among levels of impairment due to uncorrected refractive error and could be used to assess refractive programs in similar settings.

Comparative effectiveness research in rehabilitation medicine requires the development and validation of clinically meaningful and scientifically rigorous measurements of patient states and theories that explain and predict outcomes of intervention. Patient traits are latent (unobservable) variables that can be measured only by inference from observations of surrogate manifest (observable) variables. In the behavioral sciences, latent variables are analogous to intensive physical variables such as temperature and manifest variables are analogous to extensive physical variables such as distance. Although only one variable at a time can be measured, the variable can have a multidimensional structure that must be understood in order to explain disagreements among different measures of the same variable. The use of Rasch theory to measure latent trait variables can be illustrated with a balance scale metaphor that has randomly added variability in the weights of the objects being measured. Knowledge of the distribution of the randomly added variability provides the theoretical structure for estimating measures from ordinal observation scores (e.g., performance measures or rating scales) using statistical inference. In rehabilitation medicine, the latent variable of primary interest is the patient's functional ability. Functional ability can be estimated from observations of surrogate performance measures (e.g., speed and accuracy) or self-report of the difficulty the patient experiences performing specific activities. A theoretical framework borrowed from project management, called the Activity Breakdown Structure (ABS), guides the choice of activities for assessment, based on the patient's value judgments, to make the observations clinically meaningful. In the case of low vision, the functional ability measure estimated from Rasch analysis of activity difficulty ratings was discovered to be a two-dimensional variable. The two visual function dimensions are independent of physical limitations and psychological state. To explain outcome measures (latent variable estimated from difficulty ratings), a theory must be developed that explicitly defines how latent variables are related to the observed manifest variables and to each other. The latent variables are categorized as primary variables, which in the case of low vision are the two visual function dimensions, and as effect modifiers, which in the case of low vision are other physical and psychological latent traits of the patients that can influence the outcome measures. Interventions give rise to latent intervention effect variables that can alter the latent primary variables or independently affect the outcome measures. The latent effect modifier variables, in turn, can alter the latent intervention effect variables. Once developed and validated, a theory of this form will predict the rehabilitation potential of individual patients, i.e., the probability of obtaining criterion outcome measures given the observed state of the patient and the choice of interventions.

Objective To evaluate the effects of cataract extraction with intraocular lens implantation (CE-IOL) in low-vision patients. Design Prospective, interventional case series. Participants Twenty low-vision patients (30 eyes) underwent CE-IOL by 1 surgeon at an academic institution. Methods Pre- and post-CE-IOL visual acuities and responses to a 23-page survey (self-reported functioning in general vision, mobility, illumination, and ability to see faces) were compared. Results Sixteen patients had age-related macular degeneration (AMD); 1 patient each had rod-cone dystrophy, oculocutaneous albinism, retinitis pigmentosa, or cerebrovascular accident. The average age was 78 years (range: 53-96 years). Preoperative best-corrected visual acuity (BCVA) ranged from 20/70 to count fingers; postoperative BCVA at 8 weeks was 20/40 to 20/400, with improvement in 25 (83%) eyes of 15 patients, and no change in the rest. The average change in logMAR of BCVA in the 1 eye or in the eye with better preoperative vision in bilateral surgery was an improvement of 0.6 logMAR units ( p = 0.0001). Seventeen (85%) patients noted an improvement in visual function and would consent to CE-IOL again. Twelve patients completed the survey pre- and post-CE-IOL at 3 months. More patients could read with a magnifier after surgery. On average, self-reported functioning was improved. Conclusions In this small study, CE-IOL offered subjective and objective benefits to patients from a low vision clinic, many of whom may have been dissuaded from CE-IOL. Most patients had moderately dense cataracts and moderate to advanced AMD, and these features may help form clinical recommendations. Expectations are important to elicit preoperatively. Postoperatively, patients may be more receptive to low-vision services and devices when the prognosis for visual rehabilitation is better.

The value of a diagnostic test for an individual patient is expressed in terms of the test's ability to determine whether the patient does or does not have a disease. For diagnostic tests with a continuous diagnostic variable, various decision thresholds can be selected to adjust the sensitivity and specificity of the diagnostic test to conform with the clinician's concerns (e.g., health costs, financial costs, and diagnostic information of the test). Three methods of statistical decision theory and information theory are presented for critically evaluating the value of a clinical diagnostic test. To provide an example of the application of the three methods we critically evaluate the value of using intraocular pressure (IOP) data from three populations: open angle glaucoma, open angle glaucoma suspect, and no open angle glaucoma. Based on these methods, IOP data are shown to provide a means of indicating the higher probability of the presence of open angle glaucoma (whereupon the clinician would need to conduct further diagnostic tests), but on average IOP data are shown to have very little value as a diagnostic variable.

Visual increment thresholds measured on backgrounds flashed on simultaneously with the test flash exhibit saturation rather than following Weber’s law. These flash-on-flash thresholds have been modeled with saturating nonlinearities similar to those used to describe intensity-response functions of retinal neurons. Recently, the flash-on-flash technique has been used to assess the mechanisms of threshold elevations in visual system diseases. However, the results were interpreted in a qualitative way. This paper extends the clinical application of flash-on-flash threshold measures by providing a theoretically derived algorithm for estimating nonlinear model parameters from flash-on-flash threshold data. The performance of the algorithm is evaluated with Monte Carlo techniques, and the theoretical interpretations of the model parameters are tested experimentally. Published clinical flash-on-flash threshold data are reanalyzed using the algorithm. A previously unappreciated decrease in the half-saturation constant of retinitis pigmentosa patients was revealed by this analysis.

The Wilmer fundus camera stimulator has been designed to allow testing of visual function at precise retinal locations under direct visualization. We use a modified fundus camera with a deep red source and IR vidicon to allow for both low levels of illumination and visualization of the fundus. The stimulus location is plotted directly on a real-time digitized image of the fundus using computer-generated graphics, and fixation can be monitored as testing proceeds. The fundus image with stimulus location can be stored on floppy disk for later retrieval and analysis. Both static and kinetic perimetry can be performed. This paper describes the fundus camera stimulator in detail, compares it to existing types of fundus perimeters, and provides clinical examples of its use.

The Johns Hopkins Wilmer Eye Institute and the NASA Stennis Space Center are collaborating on the development of a new high technology low vision aid called the Low Vision Enhancement System (LVES). The LVES consists of a binocular head-mounted video display system, video cameras mounted on the head-mounted display, and real-time video image processing in a system package that is battery powered and portable. Through a phased development approach, several generations of the LVES can be made available to the patient in a timely fashion. This paper describes the LVES project with major emphasis on technical problems encountered or anticipated during the development process.

To examine the effects of bias and distortion from general health status on Rasch model-based measurements of visual function, and establish measurement equivalence across different health status groups in low vision patients.Self-reported data were obtained from 1746 low vision patients who completed the Activity Inventory (AI) and an intake health-related questionnaire prior to their first visit to the low vision rehabilitation service. Differential Item Functioning (DIF) analysis by health status and separate Rasch analyses adjusted by health status were performed on the responses to both a DIF-free scale and the full scale of the AI.Of 48 Goal-level items, only 15 items showed significant DIF (P0.001). Comparing the vision-related estimates from the original full set of items with those from the DIF free scale; we found that only 25% of the person measure estimates differed by 0.5 logits or more and there was a strong intraclass correlation between the two scales in measuring the patients' vision-related functional ability (IC = 0.75). Patients' health status influenced the Rasch model based estimation of visual function by the AI (ANOVA, p = 0.005), but this effect was within accepted range of MISFIT statistics.Taken together, our results indicate that despite confounding effects of general health status on vision-related ability, we can still regard visual ability to be a single theoretically constructed variable for the low vision population. It appears that self-perceived comorbidities add to vision-related disability, but do not distort its measurement.

PURPOSE. A retrospective case-matched study designed to compare patients with diabetic retinopathy (DR) and other ocular diseases, managed in a low-vision clinic, in four different types of functional vision. METHODS. Reading, mobility, visual motor, and visual information processing were measured in the patients (n = 114) and compared with those in patients with other ocular diseases (n = 114) matched in sex, visual acuity (VA), general health status, and age, using the Activity Inventory as a Rasch-scaled measurement tool. Binocular distance visual acuity was categorized as normal (20/12.5-20/25), near normal (20/32-20/ 63), moderate (20/80-20/160), severe (20/200-20/400), profound (20/500-20/1000), and total blindness (20/1250 to no light perception). Both Wilcoxon matched pairs signed rank test and the sign test of matched pairs were used to compare estimated functional vision measures between DR cases and controls. RESULTS. Cases ranged in age from 19 to 90 years (mean age, 67.5), and 59% were women. The mean visual acuity (logMar scale) was 0.7. Based on the Wilcoxon signed rank test analyses and after adjusting the probability for multiple comparisons, there was no statistically significant difference (P > 0.05) between patients with DR and control subjects in any of four functional visions. Furthermore, diabetic retinopathy patients did not differ (P > 0.05) from their matched counterparts in goal-level vision-related functional ability and total visual ability. CONCLUSIONS. Visual impairment in patients with DR appears to be a generic and non-disease-specific outcome that can be explained mainly by the end impact of the disease in the patients' daily lives and not by the unique disease process that results in the visual impairment.

As part of a study of 198 residents with low vision in 28 nursing homes, 91 participated in a low vision rehabilitation intervention. Among the rehabilitation participants, 78% received simple environmental modifications, such as lighting; 75% received low vision instruction; 73% benefited from staff training; and 69% received simple nonoptical devices. Because of the cognitive and physical fragility of many nursing home residents, the authors recommend an approach that centers on training nursing home staff and improving the environment of the facilities, especially in the area of illumination.

There are dozens of visual function questionnaires (VFQs). VFQs differ in number of items, item content, and response categories. Despite differences, all VFQs are designed to measure vision-related functional ability in visually impaired people. The objective is to determine whether four popular VFQs measure the same variable in visually impaired patients.Two of four VFQs (ADVS, NEI-VFQ, VF-14, VAQ) plus the SF-36 were administered by telephone to 407 consecutive low vision clinic patients. Thus, each instrument was administered to just over 200 patients, and there were over 67 patients for each of the 6 pairings of VFQs. Separate Rasch analyses were performed on patient responses to each VFQ and to the physical and mental health domains in the SF-36.Person measure estimates from the four VFQs were highly correlated. Person measures estimated from the mental health and physical domains of the SF-36 were uncorrelated with each other and with person measures estimated from the VFQs. From principal components analysis we concluded that three factors were necessary and sufficient: the first principal component accounts for 62% of the variance, the other two factors account for 16% and 14% of the variance, respectively. The VFQs load most heavily on the first factor; the mental health component of the SF-36 loads most heavily on the second; and the physical limitations component of the SF-36 loads most heavily on the third.The four VFQs measure the same vision-related functional ability variable in low vision patients that is separate from and independent of the physical and mental health variables measured by the SF-36.

This study was conducted to demonstrate use of a simple scoring algorithm for the 48-item Veterans Affairs Low Vision Visual Functioning Questionnaire (VA LV VFQ-48) that approximates the measure of persons' visual ability that would be calculated with Rasch analysis and to provide a short form version of the questionnaire for clinical practice and outcomes research.Items were eliminated from the VA LV VFQ-48 to reduce redundancy and shorten the instrument. The approximation of persons' visual ability calculated with the scoring algorithm for vision function questionnaires developed by Massof was compared with the person measure estimated from Rasch analysis for a sample of 126 subjects entering a low vision rehabilitation program.The approximation captures 98% of the variability in the Rasch measure estimate of persons' visual ability and 97% of the variability in the change score estimate. The relationship does not hold in circumstances where patients with high visual ability find most items to be easy. A 20-item short form of the instrument was constructed for use in low vision service delivery.The scoring algorithm can be used with the VA LV VFQ-48 or short form versions of the questionnaire. Clinicians can use the algorithm to score the VA LV VFQ from examination of individual patients or as an outcome measure for their low vision rehabilitation programs. Research investigators can use the scoring algorithm with small samples when Rasch analysis is not reliable or in studies where Rasch analysis is not practical. Rasch analysis is still recommended for research studies that require more accurate assessments.

Purpose The primary purpose of the study is to present and test a simple algorithm for scoring visual function questionnaires (VFQs) that approximates person measure estimates from Rasch analysis, does not introduce nonlinearities at extreme scores, and is insensitive to missing data. A secondary purpose is to test the hypothesis that all VFQs measure the same visual ability variable and can be calibrated to a common measurement scale. Methods Each of 407 consecutively recruited low vision patients were administered two of four visual function questionnaires: Activities of Daily Living Scale (ADVS), National Eye Institute Visual Functioning Questionnaire (NEI VFQ), 14-item Visual Functioning Index (VF-14), Visual Activities Questionnaire (VAQ). Separate Rasch analyses, using the Andrich rating scale model, were performed on responses to each of the four VFQs and again on the merged data of all instruments. An approximation of visual ability, based on average functional reserve and an inverse hyperbolic tangent transformation, is presented and tested by comparing visual ability estimates from the Rasch analyses to corresponding estimates from the approximations. Results Relative to person measure estimates from Rasch analysis, the approximations were observed to be linear and highly reliable (intraclass correlations ranged from 0.97 to 0.997). The measurement scale of each of the four instruments was observed to be a linear transformation of the measurement scale estimated from the merged responses of all four instruments. The approximation algorithm transforms rating scale responses for each instrument to a common measurement scale. By randomly censuring item responses for each subject, it was demonstrated that the approximation algorithm is robust and insensitive to missing data. Conclusions A simple scoring algorithm based on an inverse hyperbolic tangent transformation of average functional reserve produces highly reliable approximations of visual ability estimated from Rasch analysis for the ADVS, NEI VFQ, VAQ, and VF-14. All four instruments measure the same visual ability variable in units that can be calibrated to a common measurement scale.

To evaluate the natural course of visual field loss in patients with Type 2 Usher syndrome and different patterns of visual field loss.Fifty-eight patients with Type 2 Usher syndrome who had at least three visual field measurements during a period of at least 3 years were studied. Kinetic visual fields measured on a standard calibrated Goldmann perimeter with II4e and V4e targets were analyzed. The visual field areas in both eyes were determined by planimetry with the use of a digitalizing tablet and computer software and expressed in square inches. The data for each visual field area measurement were transformed to a natural log unit. Using a mixed model regression analysis, values for the half-life of field loss (time during which half of the remaining field area is lost) were estimated. Three different patterns of visual field loss were identified, and the half-life time for each pattern of loss was calculated.Of the 58 patients, 11 were classified as having pattern type I, 12 with pattern type II, and 14 with pattern type III. Of 21 patients whose visual field loss was so advanced that they could not be classified, 15 showed only a small residual central field (Group A) and 6 showed a residual central field with a peripheral island (Group B). The average half-life times varied between 3.85 and 7.37 for the II4e test target and 4.59 to 6.42 for the V4e target. There was no statistically significant difference in the half-life times between the various patterns of field loss or for the test targets.The average half-life times for visual field loss in patients with Usher syndrome Type 2 were statistically similar among those patients with different patterns of visual field loss. These findings will be useful for counseling patients with Type 2 Usher syndrome as to their prognosis for anticipated visual field loss.

Stelmack JA, Moran D'A, Dean D, Massof RW. Short- and long-term effects of an intensive inpatient vision rehabilitation program. Objective To assess the effects of a visual rehabilitation program on visually impaired subjects' visual ability and ability to perform activities. Design Prospective observational study. Setting Telephone interviews of respondents in their homes the week before admission to the rehabilitation center and 3 months and 1 year after discharge from the rehabilitation center. Participants A total of 178 consecutive patients from the Hines Blind Rehabilitation Center participated in development of the 48-item Veterans Affairs Low Vision Visual Functioning Questionnaire (VA LV VFQ-48). Data were analyzed for 95 who participated in all 3 administrations of the questionnaire. Intervention Comprehensive blind rehabilitation program (mean hospital admission, 40d). Main Outcome Measure The self-report ratings of patients' difficulty performing 48 activities on the VA LV VFQ-48. Results The increase in visual ability ± standard deviation of .981±.482 logits (equivalent to an 8-line improvement in visual acuity on an Early Treatment of Diabetic Retinopathy Study chart) at 3 months postrehabilitation decreased to .682±.485 logits (equivalent to a loss of 2.5 lines of visual acuity on the same chart) 1 year postrehabilitation. The effect sizes measured at 3 months (2.035) and 1 year (1.495) indicate large treatment effects corresponding to statistically significant differences for the increase in visual ability at 3 months and 1 year postrehabilitation (paired 2-tailed t tests, P P Conclusions Treatment effects decreased over the 12-month follow-up period. However, the group of patients whose data were analyzed was still statistically and clinically significantly better at their 1-year follow-up than before beginning treatment.

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.

To compare the uptake of cataract surgery in nursing homes in which assistance was provided in obtaining services with that in control homes.The Salisbury Eye Evaluation in Nursing Home Groups (SEEING) project is a randomized clinical trial studying the effect of a comprehensive vision restoration-rehabilitation program, including the provision of cataract surgery services when needed. Twenty-eight nursing homes in the Eastern Shore area of Maryland and Delaware were matched in pairs by size and payment type. Nursing homes within each pair were randomized to usual care or targeted intervention. Persons with cataract causing visual acuity in the better eye to be worse than 20/40 were informed of the possible benefit of cataract surgery. For those in intervention homes, additional support was provided in obtaining cataract surgery.Of residents with vision-impairing cataract in intervention homes, 31% underwent cataract surgery vs 2% in usual-care facilities. Residents with cataract compared with all residents without visual impairment, regardless of nursing home assignment, tended to be older (mean age, 86.7 vs 82.1 years; P.001), were more likely to be black (age-adjusted P.001), had lower Mini-Mental State Examination scores (mean, 11.7 vs 16.2; age-adjusted P.001), and longer length of stay (mean, 42.3 vs 24.4 months; P.001). Furthermore, cataract was associated with significant visual impairment and with functional limitations, with 20% of those recommended for surgery having a visual acuity of 20/100 or worse in the better-seeing eye.Screening for and identifying cataracts as a cause of vision loss rarely results in uptake of cataract surgery services in nursing homes. The addition of a support system to facilitate the process of scheduling surgery and getting to and from the hospital dramatically increases uptake rates.

The National Institutes of Health (NIH) includes visual impairment in the 10 most prevalent causes of disability in America. As rehabilitation programs have the potential to restore independence and improve the quality of life for affected persons, NIH research priorities include evaluating their effectiveness. This paper demonstrates a clinical perspective on the use of the Rasch person-item map to evaluate the range and precision of a new vision function questionnaire in early analysis (prior to full sample). A self-report questionnaire was developed to measure the difficulty that persons with different levels of vision loss have performing daily activities. This 48-item Veterans Affairs Low-Vision Visual Functioning Questionnaire (VA LV VFQ-48) was administered to 117 low-vision patients. Preliminary analysis indicates that the questionnaire items are applicable to persons of differing abilities. The Rasch person-item map demonstrates that the field-test version of the VA LV VFQ-48 has good range and is well centered with respect to the person measure distribution. Construct validity and reliability are also demonstrated.

PURPOSE. To describe psychometric properties of a self-report questionnaire, the Veterans Affairs (VA) Low-Vision Visual Functioning Questionnaire (LV VFQ-48), which was designed to measure the difficulty visually impaired persons have performing daily activities and to evaluate low-vision outcomes. METHODS. The VA LV VFQ-48 was administered by telephone interview to subjects with visual acuity ranging from near normal to total blindness at five sites in the VA and private sector. Rasch analysis with the Andrich rating scale model was applied to difficulty ratings from 367 subjects, to evaluate measurement properties of the instrument. RESULTS. High intercenter correlations for item measure estimates (intraclass correlation coefficient [ICC] 0.97) justified pooling the data from these sites. The person measure fit statistics (mean square residuals) confirm that the data fit the assumptions of the model. The item measure fit statistics indicate that responses to 19% of the items were confounded by factors other than visual ability. The separation reliabilities for pooled data (0.94 for persons and 0.98 for items) demonstrate that the estimated measures discriminate persons and items well along the visual ability dimension. ICCs for test‐retest data (0.98 for items and 0.84 for persons) confirm temporal stability. Subjects used the rating categories in the same way at all five centers. Ratings of slight and moderate difficulty were used interchangeably, suggesting that the instrument could be modified to a 4-point scale including not difficult, slightly/moderately difficult, extremely difficult, and impossible. Fifty additional subjects were administered the questionnaire with a 4-point scale to confirm that the scale was used in the same way when there were four rather than five difficulty ratings. CONCLUSIONS. The VA LV VFQ-48 is valid and reliable and has the range and precision necessary to measure visual ability of low-vision patients with moderate to severe vision loss across diverse clinical settings. (Invest Ophthalmol Vis Sci. 2004;45: 3919‐3928) DOI:10.1167/iovs.04-0208

Sensory engineering is defined to be the science and technology of synthetic environments. This emerging discipline incorporates such technologies as virtual environments and virtual reality, data visualization, human sensory system modeling, human-machine interface, and perception, cognition and performance characterization. An educational curriculum requires basic science in the fields of computer science, electrical engineering, psychology, physiology, the biomedical sciences, and mathematics. The authors present the plan for a multidivisional graduate education program in sensory engineering, being developed at the Johns Hopkins University, within the Schools of Arts and Sciences, Engineering, Medicine, and the Applied Physics Laboratory. >

To evaluate the sensitivity of the National Eye Institute Visual Functioning Questionnaire-25 (NEI VFQ-25) to change in visual abilities after low-vision rehabilitation in two different Veterans Administration (VA) low-vision programsSeventy-seven legally blind veterans from the Blind Rehabilitation Center (BRC) at Hines VA Hospital and 51 partially sighted veterans from the Visual Impairment Center to Optimize Remaining Sight (VICTORS) program at the Chicago Health Care Network, West Side Division, were administered the NEI VFQ-25 plus supplement in interview format at admission and discharge. Instructions for administration were modified to have study participants answer all the questions as if they were wearing glasses or contact lenses or were using low-vision devices. Interval measures of person ability and item difficulty were estimated from the patients' responses to 34 of the 39 items on the VFQ-25 plus supplement before and after rehabilitation, by the polytomous rating scale measurement model of Wright and Masters.In VICTORS patients, item order by difficulty before rehabilitation agreed with item order for BRC patients. Visual ability scales are used similarly by different patients with different degrees of low vision. Based on prerehabilitation person measure distributions, VICTORS patients were less disabled, as would be predicted by visual acuity, than were BRC patients. After rehabilitation, estimated item difficulty for 4 of the 34 items decreased significantly in both BRC and VICTORS patients.The present study demonstrates that the NEI VFQ-25 plus supplement can be used to measure the effects of low-vision rehabilitation; however, only 7 of the 34 items tested are sensitive to change after rehabilitation. Targeted activities, such as reading ordinary print, small print, and street signs are easier to perform for graduates of both programs after rehabilitation. The patients' visual ability also shows improvement in both BRC and VICTORS. Improvement in visual ability is independent of change in difficulty of targeted items. Although this was not a controlled clinical trial, the decrease in difficulty of targeted items may reflect the use of low-vision aids and training to make tasks easier. The change in visual ability may reflect positive outcomes of rehabilitation or may be the consequence of patients' overestimates of their functional ability at the time of discharge.

To determine whether the patient-based assessment of difficulty in mobility, developed and validated in a group of patients with retinitis pigmentosa (RP), is valid for measuring perceived visual ability for independent mobility in patients with glaucoma.A mobility questionnaire that had previously been developed was administered to 83 patient-volunteers who had various amounts of visual impairment caused by glaucoma. Each volunteer rated the perceived difficulty of walking independently in each of 35 mobility situations. A Rasch analysis of the ordinal difficulty ratings was used to estimate interval measures of perceived visual ability for independent mobility.The instrument showed good construct and content validity and high reliability scores. Criterion validity of the instrument was demonstrated by its ability to discriminate mobility-related behaviors such as fear of falling, asking for accompaniment, and believing their ability to travel independently is less than that of persons with normal vision. To make the perceived mobility scale comparable for the two diagnostic groups the questionnaire was restricted to those items whose difference in item-logit distributions was within +/-3 (18 items). Using the same instrument calibration, we compared the person measures between the patients with glaucoma and those with RP. Patients with glaucoma had, on average, higher perceived visual ability for independent mobility than those with RP.The instrument developed for patients with RP, to determine difficulty across a range of mobility situations, is a valid measure of perceived ability for independent mobility in patients with glaucoma.

To assess the performance of two approaches to visual acuity testing in a group of nursing home residents with cognitive impairment. The study was a cross-sectional comparison of the effectiveness of two tests of visual acuity.Nursing home residents participating in a clinical trial were tested with both recognition acuity charts and grating acuity cards (Teller) by masked observers.Of the nursing home residents (n = 656) who participated in the study, 86% could respond to visual acuity testing in at least one eye. Eighty-four percent were testable using Teller cards versus 73% who were testable by Early-Treatment Diabetic Retinopathy Study (ETDRS) charts or Lea symbol charts. Forty-one percent of individuals with MiniMental Status Examination (MMSE) scores lower than 10 were testable by recognition acuity, whereas 61% were testable with grating acuity cards. Grating acuity correlated well with recognition acuity (R = 0.79; 95% CI, 0.75-0.98, intraclass correlation coefficient [ICC]). The correlation was slightly lower in individuals with decreased MMSE scores. Although grating acuity was one line better than recognition acuity on average and median acuities were the same, 24% of individuals had results that differed by three or more lines.Teller acuity cards can effectively test the vision in cognitively impaired individuals who are not testable by conventional means. Grating acuity results correlated well with those of recognition acuity, although differences of three or more lines were not uncommon. Wider use of grating acuity testing allows a more complete assessment of visual function in the cognitively impaired elderly.

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.

Background Prior studies have shown age-related macular degeneration (AMD) to be associated with falls. The purpose of this study is to determine if (AMD) and AMD-related vision loss are associated with fear of falling, an important and distinct outcome. Methods Sixty-five persons with AMD with evidence of vision loss in one or both eyes and 60 glaucoma suspects with normal vision completed the University of Illinois at Chicago Fear of Falling questionnaire. Responses were Rasch analyzed. Scores were expressed in logit units, with lower scores demonstrating lesser ability and greater fear of falling. Results Compared to glaucoma suspect controls, AMD subjects had worse visual acuity (VA) (median better-eye VA = 20/48 vs. 20/24, p

Over the past two decades, more than a dozen visual function questionnaires have been offered as instruments to measure the impact of visual impairment on a person’s ability to perform common daily activities.

The basic concepts and structure of a hierarchical systems model for low vision rehabilitation is developed and presented. The model is built on the assumption that the patient has a desired life state, which is not realized because of the visual impairment. Life state is defined as a set of activities that the individual wants or needs to perform. The activities that constitute life state are represented hierarchically in a system called the activity breakdown structure (ABS). The highest level of the ABS represents the objectives served by the activities (e.g., daily living, vocational, recreational, social, and educational objectives). Under each objective is a set of goals that serve that objective. Any goal could serve multiple objectives. The requirements for successfully achieving a goal may vary with the objective that goal serves. The lowest level of the ABS consists of tasks that must be performed successfully to achieve particular goals. Any task could serve multiple goals. Each goal and each task has a value to the patient (i.e., level of importance) and also is associated with a level of difficulty. The need for rehabilitation, which is captured in the formal construct rehabilitative demand, for each goal and its subsidiary tasks, scales with the value of the goal or task and with the difficulty in achieving the goal and/or performing the task. Successful rehabilitation will reduce rehabilitative demand by reducing the level of difficulty associated with the goal or task and/or by reducing the value assigned by the patient to the goal or task (as a result of counseling or of learning alternative strategies). Within the framework of the model, changes in rehabilitative demand define effectiveness of intervention.

To evaluate the effectiveness of low-vision rehabilitation in 2 cohorts derived from the Veterans Affairs Low-Vision Intervention Trial.In a prospective study, we observed 44 participants randomly assigned to outpatient low-vision rehabilitation who did not receive additional treatment after the trial ended at 4-month follow-up and 56 participants randomly assigned to the waiting-list control group and thereafter to standard therapy. The outcome measures included visual ability domains (reading, mobility, visual information processing, and visual motor skills) and overall visual ability estimated from difficulty ratings using the 48-item Veterans Affairs Low-Vision Visual Functioning Questionnaire. Mean visual ability scores for the treatment and control groups were compared at baseline, 4 months, and 1 year. A mixed-effects model was used to test treatment effects between groups over time. Differences in visual ability mean scores from baseline to 1 year were compared between the 2 groups. Within-group changes in visual ability were compared from baseline to 1 year, from baseline to 4 months, and from 4 months to 1 year.At baseline, there were no significant differences in mean visual ability scores between groups. From baseline to 4 months, the treatment effects for all visual ability domains and overall visual ability increased to a maximum in the treatment group (P.001), whereas the mean scores (except visual motor skills) decreased in the control group (P.01). From 4 months to 1 year, the differences became smaller. There was a loss of visual ability in reading and visual information processing (but not in visual motor skills, mobility, or overall visual ability) in the treatment group and a gain in all visual ability measures in the control group. Interactions of treatment and follow-up time in the mixed models showed the trend of treatment effects significantly changed over time from baseline to 1 year (P.001) for all visual ability domains and overall visual ability. Both groups demonstrated improvement in visual ability from baseline to 1 year (P.001) (except for mobility in the control group). Overall visual ability (but not other visual ability domains) improved more in the treatment group than in the control group (P= .01).Visual ability improved significantly in both groups from baseline to 1 year. The Low-Vision Intervention Trial treatment effect is robust and well maintained for patients with macular diseases.