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A-M Montgomery, MR Stevenson, PM Hart, U Chakravarthy; Assigning subscales to the Daily Living Tasks Dependent on Vision (DLTV) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3818.
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Purpose: To assign subscales to the Daily Living Tasks Dependent on Vision (DLTV), a visual functioning questionnaire devised for use specifically in older people with AMD. Methods: One hundred and ninety-one subjects underwent visual function assessment (fully corrected distance and near acuity and contrast sensitivity in both eyes) and completed the DLTV at the same visit. Responses to 25 items within the DLTV were assigned to domains based on hierarchical cluster and factor analyses. The internal consistency of items within each of the domains was tested by reliability analysis. Intra and inter domain correlation coefficients were examined and multiple linear regression used to evaluate relationships between the domains and measures of vision. Results: We found that the items formed 4 clusters. Group 1 contained two items on light and dark adaptation. Group 2 contained items of global self rating of vision and tasks where vision interacted with mobility. Group 3 comprised tasks of visual discrimination (both near and far) and Group 4 was a complex mixture and included tasks involving stereoacuity and colour perception. Intra domain consistency tests showed that Cronbach’s alpha values were within the range 0.7 to 0.9 except in Group 3 where a value of 0.95 indicated some redundancy. Correlations between domains ranged from 0.49 to 0.86 with the lowest seen between Group 1 and the other three groups. Linear regression showed that near acuity explained most of the variation in Groups 3 and 4. Contrast in the worse eye explained most of the variation in Group 2. Cluster and factor analyses of a further independent data set of 200 AMD patients showed similar results. Conclusion: We did not find items segregating into domains on a typical intuitive basis (for example distance and near tasks or colour vision). Our results support the assigning of items to subscales using the above methods. The finding that contrast in the worse eye had a significant relationship with Group 2 tasks suggests that confidence and visual mobility are dependent on good vision in both eyes.
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