Validity of the visual function index (VF-14) in patients with retinal disease

Objective: To test the validity of the Visual Function Index (VF-14) in patients with retinal disease. Design: A self-administered questionnaire package in association with clinical examination findings. Participants: Consecutive patients attending the Vancouver General Hospital Eye Care Centre, Vancouver, British Columbia, retina clinic between May 1 and August 15, 1998. Main Outcome Measures: Responses to the questionnaire package as they relate to global self-assessment scales and visual acuity. In addition, correlations were calculated between the VF-14, the 36-Item Short-Form Health Survey, a Weighted Comorbidity Scale, and visual acuity scores. Results: Five hundred forty-seven patients were given the questionnaire package to complete. The VF-14 demonstrated a moderately strong positive association with patient self-rating of amount of trouble, satisfaction, and overall quality of vision. Correlations between the 36-Item Short-Form Health Survey, visual acuity, and the global scales were mild to moderate. The VF-14 was moderately correlated with visual acuity in the better and the worse eyes. Conclusions: This study provides support for the validity of the VF-14 as a measure of functional impairment in patients with retinal disease. Once responsiveness has been measured and an analysis of disease subtypes has been carried out, the VF-14 will be ready for inclusion in clinical trials to evaluate patients' functional ability. Further implementation and development of this outcome measure will better our understanding of the utility of the functional assessment format for patients with retinal disease.