Assessment of functional vision performance: a new test for low vision patients

Vision-related tasks in children with visual impairment: a multi-method study

Objective

Functional Vision (FV) is vital for the successful growth of children with visual impairment. However, tasks related to measuring FV have not been thoroughly studied for this population. To address this gap, this study seeks to establish a comprehensive set of vision-related tasks that consider both the difficulty levels of activities and the ages of children with visual impairment.

Methods

This study utilized a sequential multi-method design, including a scoping review, a qualitative content analysis, and a focus group. Firstly, a scoping review was conducted to identify vision-related tasks based on the literature. Then, to contextualize the vision-related tasks, a qualitative content analysis was carried out. Subsequently, a focus group was conducted to categorize the identified tasks based on their difficulty levels and the children's level of dependency. We utilized the directed content analysis method to analyze the data, using the occupational domain of the Occupational Therapy Practice Framework 4th edition (OTPF-4) as the primary framework.

Results

During the review phase, which included 22 studies, and the interview phase, which involved 16 participants, a total of 95 and 85 vision-related tasks were identified, respectively. These tasks were then categorized into 17 activities and five occupations, which included activities of daily living (ADL), instrumental activities of daily living (IADL), education, play, and participation in social activities. Among these occupations, ADL was the easiest, while participation in social activities was the most challenging. Finally, the tasks were arranged based on their difficulty level for children with visual impairment.

Conclusion

A comprehensive list of vision-related tasks has been developed based on the difficulty level of the tasks and the degree of dependency of children with visual impairment. This list can be used to develop standardized instruments for assessing FV in children with visual impairment.

Reliability and validity of the Canadian-French ecological adaptation of the weighted version of the Melbourne low-vision ADL Index

Background: The Mesure de l'impact de la déficience visuelle dans les activités quotidiennes (MIDVAQ) is the Canadian-French adaptation of the Melbourne Low-Vision ADL Index. It measures performance, personal importance and handicap situation in 16 instrumental activities requiring near vision (standardized material, part A) and in 9 self-care and domestic activities (self-report questionnaire, part B). This study aimed at measuring the MIDVAQ reliability and its relationship with measures of visual functions and functional vision.Methods: The MIDVAQ was administered twice to 100 visually impaired participants, at home, with their personal visual and non-visual aid. A second rater was present at T1. Two different versions of part A were used alternately at T1 and T2.Results: The total Handicap scale demonstrates good internal reliability (Cronbach's alpha coefficient = 0.82) and very high inter-rater and test-retest reliability (ICCs = 1.00 and 0.86). Part A alternative versions are highly comparable. Vision function measures are significantly correlated with total Handicap score, for which 48% of the variance is explained by functional vision estimates, age, and education.Conclusions: The MIDVAQ is highly valid and reliable. It can be useful to measure the functional impact of the visual impairment, its progression, and the outcomes of low vision rehabilitation services.Implications for rehabilitationEven if administered at home in an ecological way, this measure of the impact of the visual impairment in daily activities is very reliable.Given its good metric properties, this tool can be confidently used to assess the functional impact of visual impairment, outcomes of the low vision rehabilitation services, etc.This measurement tool provides complementary information to those obtained from clinical measures of visual functions, by reflecting the interaction between the functional abilities with the requirements of the environment.

Measurement properties of continuous text reading performance tests

PURPOSE

Measurement properties of tests to assess reading acuity or reading performance have not been extensively evaluated. This study aims to provide an overview of the literature on available continuous text reading tests and their measurement properties.

METHODS

A literature search was performed in PubMed, Embase and PsycInfo. Subsequently, information on design and content of reading tests, study design and measurement properties were extracted using consensus-based standards for selection of health measurement instruments. Quality of studies, reading tests and measurement properties were systematically assessed using pre-specified criteria.

RESULTS

From 2334 identified articles, 20 relevant articles were found on measurement properties of three reading tests in various languages: IReST, MNread Reading Test and Radner Reading Charts. All three reading tests scored high on content validity. Reproducibility studies (repeated measurements between different testing sessions) of the IReST and MNread of commercially available reading tests in different languages were missing. The IReST scored best on inter-language comparison, the MNread scored well in repeatability studies (repeated measurements under the same conditions) and the Radner showed good reproducibility in studies.

CONCLUSIONS

Although in daily practice there are other continuous text reading tests available meeting the criteria of this review, measurement properties were described in scientific studies for only three of them. Of the few available studies, the quality and content of study design and methodology used varied. For testing existing reading tests and the development of new ones, for example in other languages, we make several recommendations, including careful description of patient characteristics, use of objective and subjective lighting levels, good control of working distance, documentation of the number of raters and their training, careful documentation of scoring rules and the use of Bland-Altman analyses or similar for reproducibility and repeatability studies.

Characterizing functional complaints in patients seeking outpatient low-vision services in the United States

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<0.05 for all). Mobility concerns, defined as walking difficulty and out-of-home activities, showed no relationship to gender, age, or visual acuity.

CONCLUSIONS

Reading was the most commonly reported difficulty, regardless of the patient's diagnosis. Neither visual acuity nor gender were predictive of reading concerns, although, age showed a small effect. Addressing reading rehabilitation should be a cornerstone of low-vision therapy.

Visual functions and disability in diabetic retinopathy patients

PURPOSE

This study was undertaken to find correlations between visual functions and visual disabilities in patients with diabetic retinopathy.

METHOD

A cross-sectional study was carried out among 38 visually impaired diabetic retinopathy subjects at the Low Vision Clinic of B.P. Koirala Lions Centre for Ophthalmic Studies, Kathmandu. The subjects underwent assessment of distance and near visual acuity, objective and subjective refraction, contrast sensitivity, color vision, and central and peripheral visual fields. The visual disabilities of each subject in their daily lives were evaluated using a standard questionnaire. Multiple regression analysis between visual functions and visual disabilities index was assessed.

RESULT

The majority of subjects (42.1%) were of the age group 60-70 years. Best corrected visual acuity was found to be 0.73±0.2 in the better eye and 0.93±0.27 in the worse eye, which was significantly different at p=0.002. Visual disability scores were significantly higher for legibility of letters (1.2±0.3) and sentences (1.4±0.4), and least for clothing (0.7±0.3). Visual disability index for legibility of letters and sentences was significantly correlated with near visual acuity and peripheral visual field. Contrast sensitivity was also significantly correlated with the visual disability index, and total scores.

CONCLUSION

Impairment of near visual acuity, contrast sensitivity, and peripheral visual field correlated significantly with different types of visual disability. Hence, these clinical tests should be an integral part of the visual assessment of diabetic eyes.

The assessment of disability related to vision performance-based measure in diabetic retinopathy

PURPOSE

To validate a third-generation performance-based measure of visual function titled "Assessment of Disability Related to Vision" (ADREV) in a study population of patients with diabetic retinopathy.

DESIGN

Prospective, cross-sectional study.

METHODS

Patients with nonproliferative or proliferative diabetic retinopathy, free from ocular comorbidity, were recruited from a single institute and completed the ADREV, the 25-Item National Eye Institute Visual Functioning Questionnaire (VFQ-25), and a clinical ophthalmic examination. Correlation, regression, and bootstrap analysis were conducted to determine the relationship between ADREV scoring and each of the study's clinical and self-report measures of visual ability, while controlling for potential confounders.

RESULTS

Ninety-one patients with diabetic retinopathy completed the study and analysis showed that the ADREV total and subscale scores shared a stronger relationship with the clinical measures of visual function than did the VFQ total and subscale scores. Regression analysis revealed that binocular visual acuity, contrast sensitivity, and better eye visual field were the best predictors of ADREV performance.

CONCLUSIONS

The ADREV performance measure is a valid instrument for the assessment of disability related to vision in patients with diabetic retinopathy. Furthermore, the assessments provided by ADREV were more related to traditional clinical indicators of visual impairment than were the results of the self-report measure, specifically the VFQ-25.

Development of a battery of functional tests for low vision

PURPOSE

We describe the development and evaluation of a battery of tests of functional visual performance of everyday tasks intended to be suitable for assessment of low vision patients.

METHODS

The functional test battery comprises-Reading rate: reading aloud 20 unrelated words for each of four print sizes (8, 4, 2, & 1 M); Telephone book: finding a name and reading the telephone number; Medicine bottle label: reading the name and dosing; Utility bill: reading the due date and amount due; Cooking instructions: reading cooking time on a food package; Coin sorting: making a specified amount from coins placed on a table; Playing card recognition: identifying denomination and suit; and Face recognition: identifying expressions of printed, life-size faces at 1 and 3 m. All tests were timed except face and playing card recognition. Fourteen normally sighted and 24 low vision subjects were assessed with the functional test battery. Visual acuity, contrast sensitivity, and quality of life (National Eye Institute Visual Function Questionnaire 25 [NEI-VFQ 25]) were measured and the functional tests repeated. Subsequently, 23 low vision patients participated in a pilot randomized clinical trial with half receiving low vision rehabilitation and half a delayed intervention. The functional tests were administered at enrollment and 3 months later.

RESULTS

Normally sighted subjects could perform all tasks but the proportion of trials performed correctly by the low vision subjects ranged from 35% for face recognition at 3 m, to 95% for the playing card identification. On average, low vision subjects performed three times slower than the normally sighted subjects. Timed tasks with a visual search component showed poorer repeatability. In the pilot clinical trial, low vision rehabilitation produced the greatest improvement for the medicine bottle and cooking instruction tasks.

CONCLUSIONS

Performance of patients on these functional tests has been assessed. Some appear responsive to low vision rehabilitation.

A new method of assessing ability to perform activities of daily living: design, methods and baseline data

PURPOSE

To describe study protocol and baseline characteristics of initial subjects.

METHODS

Prospective study of 194 glaucoma patients. After informed consent, patients were evaluated using a third-generation, performance-based measure, Assessment of Disability Related to Vision (ADREV), nine tasks to simulate daily living activities; including: reading in reduced illumination, recognizing facial expression, detecting motion, recognizing street signs, locating objects, ambulating, placing pegs into different sized holes, telephoning, and matching socks. All patients completed clinical tests including visual acuity (Early Treatment Diabetic Retinopathy Study [ETDRS]), monocular and binocular visual fields, contrast sensitivity, stereopsis, and National Eye Institute's Visual Functioning Questionnaire (NEI VFQ-25). Main outcome measures are scores on subtests, total scores of ADREV and NEI VFQ-25.

RESULTS

Mean age was 67.1 years; 51% were female, 55% were of European extraction. Seventy-two percent had open-angle glaucoma. Visual acuity (logMAR) ranged from -0.18 to 2.20, visual field mean defect ranged from -32.68 to 2.62, Binocular field score ranged from 5 to 100 and contrast sensitivity score ranged from 0 to 1.8. While ADREV score ranges from 0 (total disability) to 63 (no disability), total ADREV score ranged from 3.0 to 61.7. Total NEI VFQ-25 score ranged from 17.8 (low score indicates incapable) to 100 (high score indicates not hindered).

CONCLUSIONS

Methodology of this study should provide information about disability caused by visual loss, specifically glaucoma, how difficulties in performing activities relate to standard clinical tests, and how they correlate to quality of life from patient's point of view. Subsequent papers will delineate findings and discuss their application.

Clinical Application of a Self-Report, Functional Independence Outcomes Measure in the DVA's Blind Rehabilitation Service

This article reports on a self-report measure of functional independence that is being used to measure outcomes of blind rehabilitation programs in the Department of Veterans Affairs (DVA). Analyses of the data have resulted in the clinical protocol that is currently in use nationally by the DVA Blind Rehabilitation Service.

Relationship between vision impairment and ability to perform activities of daily living

PURPOSE

To determine the relationship between clinical measures of vision impairment and the ability to perform activities of daily living (ADLs).

METHODS

One hundred and twenty subjects with low vision from a variety of causes participated in the study. Vision impairment was assessed under binocular conditions by measuring distance visual acuity, near word acuity, Melbourne Edge Test contrast sensitivity, Pelli-Robson Chart contrast sensitivity and visual fields. The ADL performance was assessed using the Melbourne Low Vision ADL Index (MLVAI), which is in part an observed performance assessment of instrumental ADLs and in part a self-report assessment of basic self-care ADLs.

RESULTS

All vision measures had a high, statistically significant correlation with MLVAI total score. Near word acuity, had the strongest correlation (r(s) = -0.86, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (r(s) = 0.80, p < 0.001). Visual field had the weakest correlation (r(s) = 0.56, p < 0.001). Together, age, near word acuity, Melbourne Edge Test contrast sensitivity and visual field accounted for 82.2% (adjusted R2, p < 0.001) of the variance in MLVAI total score. All correlations obtained were higher for the observed performance assessment of instrumental ADLs than for the self-report assessment of basic self-care ADLs.

CONCLUSIONS

Clinical vision impairment measures are highly correlated with capacity to perform ADLs, as measured by the MLVAI.

A weighted version of the Melbourne Low-Vision ADL Index: a measure of disability impact

OBJECTIVE

To develop a version of the Melbourne Low-Vision ADL Index that measures the personal impact of disability in activities of daily living (ADL's). Also, to determine the relationship between clinical measures of vision impairment and disability impact.

METHODS

The Melbourne Low-Vision ADL Index (MLVAI) is a desk-based clinical assessment of disability in ADL's. Ability to perform each item is rated on a five-level descriptive scale from zero to four. In this study, the original version of the MLVAI was modified to measure disability impact. The simple modification involved weighting each item by the importance of that item to the person being tested. Importance was also rated on a five-level scale from zero to four. The validity and reliability of the Weighted Melbourne Low-Vision ADL Index (MLVAI(W)) was determined for 97 vision-impaired subjects in a cross-sectional study.

RESULTS

Cronbach's alpha coefficient indicated an internal reliability of 0.94, and an intraclass correlation coefficient indicated an overall reliability of 0.88. The standard error of measurement was 24.7 points (out of a possible score of 400). There was a statistically significant difference in test scores between normal subjects and vision-impaired subjects. All vision measures had a high, statistically significant correlation with MLVAI(W) score. Near-word acuity had the strongest correlation (r(s) = 0.78, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (r(s) = -0.72, p < 0.001). Visual field had the weakest correlation (r(s) = -0.52, p < 0.001). The best predictive model of MLVAI(W) score incorporated the variables age, near-word acuity, and visual field. Together, these variables accounted for 65.1% of the variance in MLVAI(W) score.

CONCLUSIONS

The MLVAI is highly valid and reliable when weighted by a scale that reflects the personal importance of ADL's. The MLVAI(W) can provide information over and above that obtained with the usual clinical vision measures and may be used to assess low-vision patients and to measure low-vision rehabilitation outcomes. It is suggested that the assessment of disability using the original MLVAI and the assessment of the impact of disability using the MLVAI(W) should be kept separate to facilitate the clear interpretation of the outcomes of low-vision rehabilitation.

Preliminary investigation of the responsiveness of the Melbourne Low Vision ADL index to low-vision rehabilitation

PURPOSE

To conduct a preliminary investigation on the ability of the Melbourne Low Vision ADL Index to detect changes in functional ability as a result of low-vision rehabilitation.

METHODS

Twenty two subjects with age-related macular degeneration (ARMD) who were newly referred to the Kooyong Low Vision Clinic were recruited. The Melbourne Low Vision ADL Index was administered prerehabilitation and postrehabilitation. Changes in scores and effect size statistics were analyzed.

RESULTS

The median total score for the subjects prerehabilitation was 67, and the median total score postrehabilitation was 76. The difference in prerehabilitation and postrehabilitation scores was statistically significant (Wilcoxon signed rank test = 248.5, p < 0.001). The mean change score for the total Melbourne Low Vision ADL Index was 9.3 (SD, 5.6). Thus the overall effect size statistic (mean change score divided by SD of prerehabilitation score) was 0.78.

CONCLUSIONS

This preliminary investigation indicates that the Melbourne Low Vision ADL Index is responsive to a rehabilitation program for patients with ARMD. It has potential to be used as a measure of low-vision rehabilitation outcomes.

Timed instrumental activities of daily living tasks: relationship to visual function in older adults

PURPOSE

To identify instrumental activities of daily living (IADL) tasks whose completion time is related to visual function in older adults.

METHODS

Visual function (acuity, contrast sensitivity, and useful field of view) and the time to complete 17 visual tasks of everyday life were measured in a sample of 342 older adults (mean age 71 years, range 56 to 86) recruited from eye clinics. The timed IADL (TIADL) tasks included a variety of visual activities such as reading ingredients on cans of food and instructions on medicine bottles, finding a phone number in a directory, locating items on a crowded shelf and in a drawer, and using a screwdriver.

RESULTS

Multiple regression analysis indicated that poorer scores for acuity, contrast sensitivity, and useful field of view were independently associated with longer times to complete visual TIADL tasks, even after adjusting for age, educational level, depression, and general health. Cognitive status also had a significant, independent association with timed task performance.

CONCLUSIONS

Older adults' timed performance in everyday tasks is related to various aspects of visual function independent of the influences of other functional and health problems and advanced age. This suggests that TIADL tasks may eventually be useful as performance outcomes in intervention evaluations targeted at reversing vision impairment or minimizing its impact. To understand the relationship between vision impairment and TIADL task performance in older adults, cognitive impairment needs to be taken into account because it has a relatively strong and independent relationship with visual TIADL task performance.

A practical guide to low vision management of patients with diabetes

iabetic retinopathy is the leading cause of low vision and blindness in developed countries. Optometrists have an important role in the detection of diabetic-related eye disease. They are also well-placed to manage patients with reduced vision due to diabetes. In 1998, visual rehabilitation information was analysed from 590 visually impaired patients attending the multidisciplinary Low Vision Clinic at Kooyong in Melbourne, Australia. Diabetes was the primary cause of vision loss in 43 (7.3 per cent) of the patients. This paper investigates the characteristics of these 43 patients and the strategies employed to assist them. In doing so we hope to assist practitioners in managing patients with low vision due to diabetes.

Design of the low vision quality-of-life questionnaire (LVQOL) and measuring the outcome of low-vision rehabilitation

PURPOSE

To design and validate a vision-specific quality-of-life assessment tool to be used in a clinical setting to evaluate low-vision rehabilitation strategy and management.

METHODS

Previous vision-related questionnaires were assessed by low-vision rehabilitation professionals and patients for relevance and coverage. The 74 items selected were pretested to ensure correct interpretation. One hundred and fifty patients with low vision completed the chosen questions on four occasions to allow the selection of the most appropriate items. The vision-specific quality of life of patients with low vision was compared with that of 70 age-matched and gender-matched patients with normal vision and before and after low-vision rehabilitation in 278 patients.

RESULTS

Items that were unreliable, internally inconsistent, redundant, or not relevant were excluded, resulting in the 25-item Low Vision Quality-of-Life Questionnaire (LVQOL). Completion of the LVQOL results in a summed score between 0 (a low quality of life) and 125 (a high quality of life). The LVQOL has a high internal consistency (alpha = 0.88) and good reliability (0.72). The average LVQOL score for a population with low vision (60.9 +/- 25.1) was significantly lower than the average score of those with normal vision (100.3 +/- 20.8). Rehabilitation improved the LVQOL score of those with low vision by an average of 6.8 +/- 15.6 (17%).

CONCLUSIONS

The LVQOL was shown to be an internally consistent, reliable, and fast method for measuring the vision-specific quality of life of the visually impaired in a clinical setting. It is able to quantify the quality of life of those with low vision and is useful in determining the effects of low-vision rehabilitation.

Evaluating the effectiveness of a vision rehabilitation intervention using an objective and subjective measure of functional performance

PURPOSE

To test the hypothesis that vision rehabilitation using optometry, occupational therapy and social work services increases patients' functional ability and to assess whether involving families in the intervention results in more successful outcomes.

METHODS

We conducted an outcome study of 97 patients new to the Vision Rehabilitation Service. Subjects were between the ages of 19 and 91 years, with a median age of 76. Their visual acuities were 20/100 or worse in the better eye, with 50% of the subjects having acuities worse than 20/200. Macular degeneration was the most prevalent diagnosis. Subjects were assigned to either an individually focused (n=48) or a family focused (n=49) intervention. The outcome measure was change in function, as assessed by speed and accuracy of performance (objective measure) and by the patients' self-reports of difficulty and dependency in performing daily activities (subjective measures). Data were collected before and after the intervention.

RESULTS

Most patients had documented improvement after rehabilitation on both objective (p=.0001) and subjective (decreased dependency, p=.01) measures of function. The sample size did not provide adequate statistical power to show differences between family focused and individually focused interventions.

CONCLUSIONS

This study documents significant improvement after vision rehabilitation for a predominantly elderly population. Patients in both family and individually focused interventions improved comparably.