Rasch analysis of the student refractive error and eyeglass questionnaire

PURPOSE: To evaluate and refine a newly developed instrument, the Student Refractive Error and Eyeglasses Questionnaire (SREEQ), designed to measure the impact of uncorrected and corrected refractive error on vision-related quality of life (VRQoL) in school-aged children. METHODS: A 38-statement instrument consisting of two parts was developed: part A relates to perceptions regarding uncorrected vision and part B relates to perceptions regarding corrected vision and includes other statements regarding VRQoL with spectacle correction. The SREEQ was administered to 200 Native American 6th- through 12th-grade students known to have previously worn and who currently require eyeglasses. Rasch analysis was conducted to evaluate the functioning of the SREEQ. Statements on parts A and B were analyzed to examine the dimensionality and constructs of the questionnaire, how well the items functioned, and the appropriateness of the response scale used. RESULTS: Rasch analysis suggested two items be eliminated and the measurement scale for matching items be reduced from a four-point response scale to a three-point response scale. With these modifications, categorical data were converted to interval-level data to conduct an item and person analysis. A shortened version of the SREEQ was constructed with these modifications, the SREEQ-R, which included the statements that were able to capture changes in VRQoL associated with spectacle wear for those with significant refractive error in our study population. CONCLUSIONS: Although part B of the SREEQ appears to have a less-than-optimal reliability to assess the impact of spectacle correction on VRQoL in our student population, it is able to detect statistically significant differences from pretest to posttest on both the group and individual levels to show that the instrument can assess the impact that glasses have on VRQoL. Further modifications to the questionnaire, such as those included in the SREEQ-R, could enhance its functionality.