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The development of the Melbourne low-vision ADL index: a measure of vision disability
S A Haymes1, A W Johnston, A D Heyes
1Department of Optometry and Vision Sciences, The University of Melbourne, Keppel and Cardigan Streets, Carlton, Victoria, Australia 3053. s.haymes@optometry.unimelb.edu.au
Purpose:
To develop a new test of activities of daily living (ADLs) appropriate for the low-vision population: the Melbourne Low-Vision ADL Index (MLVAI).
Methods:
The MLVAI was designed as a desk-based clinical assessment, comprising 18 observed items on complex ADLs in part (a) and 9 questions on broad self-care ADLs in part (b). Each item was rated on a five-level descriptive scale from 0 to 4, based on independence, speed, and accuracy of performance. It was designed to be administered under standardized conditions with regard to the instructions, illumination, and working distances. The validity and reliability of the new MLVAI was determined for 122 subjects who were representative of the general low-vision population, in a cross-sectional study.
Results:
Two items were found to be redundant and were eliminated from the test. Thus, the final test comprised 25 items, with 100 being the highest possible score. Cronbach's alpha indicated an internal reliability of 0.96, and an intraclass correlation coefficient indicated an overall reliability of 0.95. The SE of measurement was 4.5. According to Spearman's correlation coefficient, the test-retest reliability was 0.94 (P < 0.001), and the interpractitioner reliability for five different pairs of practitioners was 0.90 or higher (P < 0.001). With regard to validity, there was a moderately high correlation with vision impairment (r = -0.68, P < 0.001). Using Rasch analysis, content validity was also demonstrated by good separation indexes (4.70 and 9.88) and high reliability scores (0.96 and 0.99) for the person and items parameters, respectively. Separate calculation of indexes and reliability scores for parts (a) and (b) indicated high content validity and reliability of each part. However, the separation indexes and reliability scores were higher for part (a) than for part (b). The correlation coefficient for part (a) and part (b) was 0.68.
Conclusions:
The MLVAI is a highly valid and reliable standardized test of ADL performance for the general low-vision population. It may be used to assess patients with low vision and has the potential to be used as a measure of low-vision rehabilitation outcomes.