The Activities of Daily Vision Scale (ADVS) for cataract surgery outcomes - re-evaluating validity with Rasch analysis


PURPOSE. The Activities of Daily Vision Scale (ADVS) has been extensively validated by traditional methodology. In the current study, Rasch analysis was used to explore further the validity of the ADVS and to determine whether improvements could be made.

METHODS. Forty-three patients with cataract underwent visual acuity (VA) and contrast sensitivity (CS) testing and completed the ADVS. The data were Rasch analyzed and the value of response scale and item reduction explored. A shortened version and the original ADVS were tested for criterion validity by determining correlations with VA and CS.

RESULTS. The ADVS data contained nonnormally distributed items and items with ceiling effects and empty response categories. Therefore, items benefited from shortening the response scale, the optimum length being three responses. There was poor targeting of item difficulty to patient ability, because many patients with cataract were sufficiently able that they had no difficulty with many activities. Items were eliminated if the task was too easy or did not fit with the overall concept of visual disability determined by the Rasch model. A reduced ADVS version was established that had adequate precision, equivalent criterion validity, and improved targeting of item difficulty to patient ability, but this version was still not ideal.

CONCLUSIONS. Despite careful traditional validation, the ADVS data contained inadequacies exposed by Rasch analysis. Through Rasch scaling, particularly with response scale reduction, the ADVS can be improved, but additional questions seem to be needed to suit the more able, including patients undergoing second eye cataract surgery. There remains a need to develop Rasch-scaled measures of visual disability for use in ophthalmic outcomes research.

Investigative Ophthalmolmology & Visual Science. July 2003; 44(7): 2892-2899
Submitted for publication October 21, 2002; revised December 17, 2002, and January 26 and February 26, 2003; accepted February 28, 2003.

Konrad Pesudovs1,
Estibaliz Garamendi1,
John P. Keeves2, and
David B. Elliott1

From the 1Department of Optometry, University of Bradford, Bradford, United Kingdom; and
the 2School of Education, Flinders University of South Australia, Bedford Park, South Australia, Australia.

Supported by a Neil Hamilton Fairley Fellowship from the National Health and Medical Research Council, Canberra, Australia (KP), and a scholarship from Johnson & Johnson Vision Care Europe (EG).



An extract from this paper can be found in Rasch Measurement Transactions 17:3 Winter 2003

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