Questionnaire offers valid measure of visual disability despite poor targeting.

The article cites the visual function questionnaire (VFQ) which offers valid measure of visual disability despite poor subject targeting. A study showed VFQ as a more valid statistical model of visual disability compared to the quality of life questionnaire (QOL). The two questionnaires were mailed to 489 catarac patients in Australia who took Rasch analysis to evaluate statistical factors like, unidimentionality, targeting and differential item functioning. The results showed VFQ has good metric properties while QOL showed poor person separation.