The Impact of Vision Impairment Questionnaire: An Evaluation of Its Measurement Properties using Rasch Analysis
Ecosse L. Lamoureux; Julie Pallant; Konrad Pesudovs; Jennifer B. Hassell; Jill Keeffe
PURPOSE: To explore the psychometric properties of the Impact of Vision Impairment scale (IVI) by using Rasch analysis. METHODS: Three hundred fourteen first-time referrals to low-vision clinics completed the 32-item IVI. The data were Rasch-analyzed with a partial credit model using RUMM2020 software (RUMM Laboratory, Perth, WA, Australia). The overall fit of the model, response scale, individual item fit, differential item functioning, unidimensionality, and person-separation reliability were assessed. RESULTS: Initially, 26 items displayed disordered thresholds. However, collapsing the response scale to three categories (4 items) and four categories (28 items) produced ordered response thresholds for all items. Four items with high proportions of missing responses, poor spread, high skewness, and deviation between observed and expected model curves were then removed. This adjustment p...
Ecosse L. Lamoureux, Julie Pallant, Konrad Pesudovs, Jennifer B. Hassell, & Jill Keeffe (2006). The Impact of Vision Impairment Questionnaire: An Evaluation of Its Measurement Properties using Rasch Analysis. Investigative Ophthalmology & Visual Science, 47(11), 4732-4732. https://doi.org/10.1167/iovs.06-0220