Psychometric Assessment of the Chinese Version of the Indian Vision Functioning Questionnaire Based on the Method of Successive Dichotomizations

PURPOSE: The purpose of this study was to assess whether a Chinese translated version of the 33-item Indian Vision Function Questionnaire (IND-VFQ-33) forms a valid measurement scale and to evaluate its psychometric properties based on the method of successive dichotomizations (MSD). METHODS: The English version of the IND-VFQ-33 was translated, back translated, and cross-culturally adapted for use in China. It was interviewer administered to patients with cataracts. MSD, a polytomous Rasch model that estimates ordered thresholds, was used to assess and optimize psychometric properties of the overall scale and three subscales separately. RESULTS: One hundred and seventy-nine patients provided complete responses. After the removal of 2 misfitting items, a revised 31-item overall scale demonstrated adequate precision (person reliability [PR] = 0.92) and no misfitting items. The general functioning subscale fit the MSD model well after removing two misfitting items. The psychosocial impact subscale and the visual symptoms subscale were not considered further due to poor measurement precision. After addressing psychometric deficiencies, a 31-item overall scale (IND-VFQ-31-CN) and a 19-item general functioning subscale (IND-VFQ-GF-19-CN) were developed. CONCLUSIONS: The original IND-VFQ-33 required re-engineering to form valid measures for use in China. The revised overall scale and general functioning subscale demonstrated adequate MSD based psychometric properties. TRANSLATIONAL RELEVANCE: The revised IND-VFQ-33 is a valid patient-reported outcome assessment for Chinese patients with cataract based on MSD analysis.