Aim: To develop and evaluate a new vision specific functional index for use in individuals with age related macular degeneration (AMD).
Methods: Following consultation with patients with AMD and healthcare professionals, a questionnaire entitled the Daily Living Tasks Dependent on Vision (DLTV) was constructed. It was administered by interview to three separate groups of individuals aged 50 years or older: people with AMD, people with cataract, and people with no visual disability. The relations between DLTV, distance visual acuity, and disorder were examined using Pearson's product moment correlation coefficients, stepwise regression, and principal component analysis.
Results: There was a positive correlation between DLTV items and distance visual acuity in the better eye. Principal component analysis showed that the DLTV has a major single dimension within it. This first principal component accounted for 59% of the variation and correlated well with distance visual acuity in the better eye. Other components were found, one of which correlated with the difference in vision in the two eyes and one which featured in the differentiation of AMD subjects from individuals with cataracts.
Conclusions: The DLTV provided information on visual impairment in patients over and above that obtained from a measure of visual acuity. It also showed that patients with AMD experience greater difficulty with daily living tasks for any given level of acuity than do patients with cataract.