Patient-reported visual function outcome in cataract surgery : test–retest reliability of the Catquest-9SF questionnaire

Purpose: To study the test–retest reliability of the Catquest-9SF questionnaire in cataract surgery. Methods: A single-centre prospective non-randomized test–retest study was conducted using the Swedish National Cataract Register and the Catquest-9SF questionnaire, which is a valid patient-reported outcome measurement tool developed and used for evaluating quality and visual disability outcome in cataract surgery. Consecutive patients (n = 144) scheduled for cataract surgery completed the Catquest-9SF twice before surgery, with a minimum of 7 days and a maximum of 14 days between the two questionnaires. A rating scale model was constructed on the basis of the questionnaires from the first measurement and used to generate scores for both the first and second measurements. The consistency was investigated by calculating intraclass correlation, Pearson correlation and a Bland–Altman plot. Internal consistency was measured using Cronbach’s alpha. Results: Analyses showed an intraclass correlation of 0.93 (95% confidence interval: 0.90–0.95), a Pearson correlation of 0.93 and Cronbach’s alpha of 0.94. The results fit well in a Bland–Altman plot. Conclusion: The test–retest reliability of the Swedish Catquest-9SF is excellent. Along with previous knowledge, this supports continued use of the Catquest-9SF in evaluating quality and outcome in cataract surgery