Responsiveness and clinically important differences for the VF-14 index, SF-36, and visual acuity in patients undergoing cataract surgery.

OBJECTIVE: To assess visual acuity (VA) and 2 questionnaires of health-related quality of life--the Visual Function 14 (VF-14) index and the Medical Outcomes Study Short Form 36 Health Survey (SF-36)--as instruments for capturing clinically important changes after cataract surgery.
DESIGN: Prospective, observational study. PARTICIPANTS: Four thousand three hundred fifty-six consecutive patients attending ophthalmologic clinics in 17 hospitals in preparation for cataract surgery were recruited.
METHODS: Clinical data were collected in the visit before the intervention and 6 weeks after surgery by ophthalmologists. Patients completed the questionnaires before surgery and 3 months after surgery. MAIN OUTCOME MEASURES: The VF-14 and SF-36 questionnaire results obtained before surgery and 3 months after the procedure and VA before the procedure and 6 weeks afterward.
RESULTS: Positive mean changes in VA (+0.47) and VF-14 results (+24.03) indicated significant improvements after cataract surgery that were not reflected in changes in SF-36 domains (from 1.86 to 5.62). Responsiveness parameters demonstrated large changes in VA and VF-14 scores but not in SF-36 domains. The minimal clinically important differences (MCID) after surgery were 0.41 for VA and 15.57 for VF-14 results; the minimal detectable change (MDC) for VF-14 was 10.81.
CONCLUSIONS: Visual acuity and VF-14 scores, but not SF-36 scores, are appropriate instruments for capturing clinically important changes after cataract surgery. The MCID and MDC values obtained herein, although not absolute thresholds, may aid in the interpretation of changes in VA and VF-14 scores.