Re-engineering the Hong Kong quality of life questionnaire to assess cataract surgery outcomes

PURPOSE: To assess psychometric properties of the Hong Kong Quality of Life Questionnaire (HKQ) using Rasch analysis and use it to assess cataract surgery outcomes. METHODS: The HKQ was interviewer administered to participants at baseline (preoperative) and 12 months of follow-up (postoperative). Rasch analysis was used to assess and improve psychometric properties of the HKQ using the preoperative data. The responsiveness of the HKQ was assessed on the stacked preoperative and postoperative data, reported with the effect size. RESULTS: One hundred ninety-nine participants (median age: 72 years; interquartile range: 65 to 78 years) with cataract completed the HKQ at the preoperative assessment. There were more women (58%) and most of the participants had bilateral cataract (83.9%). Nearly half of the participants had undergone surgery in one eye (45.2%) followed by bilateral surgery (38.7%). Psychometric assessment guided by Rasch analysis resulted into a 15-item HKQ with promising psychometric properties including adequate measurement precision (2.09), no misfitting items, near perfect targeting (-0.05), unidimensionality, and with no evidence of item bias. For those who completed the HKQ (n = 82, 41.2%) at the 12-month follow-up visit, all groups demonstrated statistically significant gains in the HKQ scores, with the highest gain in participants who had undergone bilateral surgery (effect size: 2.61). CONCLUSIONS: The 15-item HKQ was valid and psychometrically sound and might be a highly responsive instrument to measure cataract surgery outcomes in China. This study demonstrated that cataract surgery significantly improves quality of life in the Chinese population.