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 pat ients with retinal disease. Design: A self-administered questionnaire package in association with clini cal 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 relat e to global self-assessment scales and visual acuity. In addition, correlat ions were calculated between the VF-14, the 36-Item Short-Form Health Surve y, a Weighted Comorbidity Scale, and visual acuity scores. Results: Five hundred forty-seven patients were given the questionnaire pac kage to complete. The VF-14 demonstrated a moderately strong positive assoc iation with patient self-rating of amount of trouble, satisfaction, and ove rall 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 re sponsiveness 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 e valuate patients' functional ability. Further implementation and developmen t of this outcome measure will better our understanding of the utility of t he functional assessment format for patients with retinal disease.