Title:
The reliability and validity of the daily activities dependence on vision (DADV) scale to evaluate vision related functional limitations.

Abstract:
The purpose was to determine the reliability and validity of the DADV scale to evaluate vision-related functional limitations in persons over 65 years. Cross sectional study was performed to determine the reliability and validity of a questionnaire (9 items). A total of 1387 subjects were selected by random sampling. An analysis of the intra/inter-observer reliability was performed and the convergent validity with the Visual Function Index, 14 items (VF-14) was determined. The number of patients who had some difficulty in performing any of the activities was 223 (19.2%; 95%CI=16.9-21.5). The intraclass correlation coefficient (ICC) of the intra/inter-observer reliability analysis was 0.883 and 0.900, respectively. Factorial analysis demonstrated that one single factor explained 63.2% of the total variance (visual function). The scale showed a high degree of convergent validity (ICC=0.857) with the VF-14. Visual acuity showed a moderate correlation with the DADV score (r=0.366). The Rasch analysis showed a satisfactory model fit for the items. Although the DADV scale is a short questionnaire it showed high correlation with the VF-14 and moderate correlation with visual acuity. The results indicate that the scale has acceptable reliability and is valid to efficiently evaluate visual function.