Validation of the visual disability questionnaire (vdq) in india

Abstract

To validate visual disability questionnaire (VDQ) in patients with low vision in India, and explore whether the two latent traits “importance” and “difficulty” associated with performance of daily activities are valid and independent constructs. The VDQ consisting of 25 items was administered verbally to 137 subjects with low vision aged 16 to 89 years. Responses for each item were rated for importance and difficulty using a 5-category Likert scale. Rasch analysis was used to estimate interval measures of response ratings. Subjects could discriminate only three response categories for importance and difficulty. Content validity was demonstrated by good separation indices for importance (4.24..