Cataract Symptom Scale: clarifying measurement

Abstract

AIM: Previous psychometric evaluation of the Cataract Symptom Scale (CSS) focused on classic assessments of reliability and validity. The aim was to investigate the psychometric properties of the CSS using the Rasch measurement model. METHODS: 243 patients drawn from the Flinders Eye Centre cataract surgery waiting-list self-administered the CSS. Rasch analysis was used to investigate the following properties of the CSS: measurement a single construct (unidimensionality), discrimination between strata of patient ability (person separation) and targeting of item difficulty to person ability. RESULTS: The CSS discriminated between four strata of patients. However, some items did not contribute..