Abstract
PURPOSE: To develop a short form of Chinese ULV-VFQ-50 based on the ULV-VFQ-150 and compare the psychometrical properties of the two questionnaires. METHODS: We selected candidate items from the ULV-VFQ-150, considering the item response among ultra-low vision (ULV) participants, the even distribution of item measures, visual aspects, and visual domains, to construct a 50-item ULV-VFQ-50 questionnaire. Then, ULV participants were recruited to evaluate its psychometric characteristics by using Rasch analysis. RESULTS: In total, 79 out of 79 completed questionnaires of ULV-VFQ-50 were collected, of which 11 filled questionnaires were excluded because the participants' vision did not meet the inclusion criteria. Thus 68 valid questionnaires were analyzed (valid response rate 91.9%). The average age of the eligible responders was 45.0 years (standard deviation [SD] = 16.7), with 42.6% females (29/68). As per Rasch analysis, the person measures ranged from -1.74 to 4.91 logits, and the item measures ranged from -1.56 to 1.15 logits. The mean value of item difficulty was 0.00 logits, whereas the mean value of personnel distribution was -0.35 logits. The item reliability was 0.95, and the person reliability was 0.98. The items conform to unidimensionality as indicated by principal component analysis of the residuals, which showed that the first principal component unexplained only 5.5% of the total variance, and each component after that unexplained even less. CONCLUSIONS: The Chinese ULV-VFQ-50 exhibits excellent psychometric properties. The short form of Chinese ULV-VFQ, with fewer items and less administration time is better suited for clinical practice and research settings. TRANSLATIONAL RELEVANCE: The Chinese version of ULV-VFQ-50 is a reliable assessment of the visual function for people with ULV in China.