Validation of an instrument to assess visual ability in children with visual impairment in China

Objective: To validate a visual ability instrument for school-aged children with visual impairment in China by translating, culturally adopting and Rasch scaling the Cardiff Visual Ability Questionnaire for Children (CVAQC). Methods: The 25-item CVAQC was translated into Mandarin using a standard protocol. The translated version (CVAQC-CN) was subjected to cognitive testing to ensure a proper cultural adaptation of its content. Then, the CVAQC-CN was interviewer-administered to 114 school-aged children and young people with visual impairment. Rasch analysis was carried out to assess its psychometric properties. The correlation between the CVAQC-CN visual ability scores and clinical measure of vision (visual acuity; VA and contrast sensitivity, CS) were assessed using Spearman's r. Results: Based on cultural adaptation exercise, cognitive testing, missing data and Rasch metrics-based iterative item removal, three items were removed from the original 25. The 22-item CVAQC-CN demonstrated excellent measurement precision (person separation index, 3.08), content validity (item separation, 10.09) and item reliability (0.99). Moreover, the CVAQC-CN was unidimensional and had no item bias. The person–item map indicated good targeting of item difficulty to person ability. The CVAQC-CN had moderate correlations between CS (−0.53, p