Psychometric Assessment of the Metamorphopsia Questionnaire in Patients with Macular Diseases Receiving Anti-Vascular...

Background: The metamorphopsia questionnaire (MeMoQ) is an established patient-reported outcome measure (PROM) in the context of macular disease. However, its performance has not been proved in those being treated for various macular conditions with intravitreal anti-vascular endothelial growth factor (Anti-VEGF). The objective was to eliminate misfitting items, enhance measurement precision, and ensure optimal response categorisation. Methods: Rasch analysis was performed iteratively on 2286 responses from patients with macular diseases being treated with Anti-VEGF to optimise the MeMoQ. Fit statistics, reliability indices, person and item separation measures, and principal component analysis (PCA) of residuals were assessed to determine the optimal model. This study was conducted in an outpatient clinic specialising in retinal diseases in Hywel Dda University Health Board. Results: Misfitting items were removed in successive iterations, leading to optimised category probability curves and stable fit statistics for the MeMoQ. The resulting model for all responses included two final items, with person separation remaining inadequate reducing from 1.23 to 1.12 and reliability from 0.60 to 0.56. Category probability curves demonstrated good ordering of response variables with Andrich thresholds separated by >1.2 logits. In the subgroups of neovascular age-related macular degeneration and diabetic macular oedema person separation remained below two and reliability remained low. Conclusions: Rasch analysis demonstrated that the MeMoQ was not a valid or reliable PROM in this patient population. Therefore, the MeMoQ may not provide a reliable index of patient's perception and visual experience when undergoing Anti-VEGF treatment.