REPRODUCIBILITY AND RESPONSIVENESS OF THE VF-14 - AN INDEX OF FUNCTIONAL IMPAIRMENT IN PATIENTS WITH CATARACTS

Objective: To assess the test-retest reliability and responsiveness of the VF-14, which is an index of functional impairment in patient with cataracts. Design: Observational longitudinal study. Patients were en rolled prior to undergoing their first cataract surgery between July 1 5 and December 15, 1991, and they were followed up for 1 year after su rgery. Setting: Patients were recruited from 72 ophthalmologists' prac tices in three US cities. Patients: Five hundred fifty-two patients wh o had undergone a surgical procedure in only one eye by the 4-month po stoperative follow-up (responsiveness analyses) and a subset of these (n = 426) who had not subsequently undergone surgery for the second ey e by the 12-month postoperative follow-up (reproducibility analyses). Main Outcome Measures: Two health status measures (the VF-14 and the S ickness Impact Profile, two global measures of a patient's trouble and satisfaction with his or her vision, and best corrected visual acuity in each eye. Results: The VF-14 is highly reproducible, with an intra class correlation coefficient of .79 when patient-rated criteria are u sed to define stable patients. The intraclass correlation coefficient was lower (.57 to .71) when various measures of visual acuity were use d to define stable patients. The VF-14 is also about three times more responsive to a change in vision than the Sickness Impact Profile, whi ch is a generic health status measure (effect size of approximately 1. 00 vs 0.30). Estimates of the responsiveness of the VF-14 and the Sick ness Impact Profile were not associated with preoperative visual acuit y in the operated on or better eye. Responsiveness of the VF-14, howev er, was higher in patients with greater self-rated trouble with vision preoperatively. Conclusions: The VF-14 was reproducible in stable pat ients during an 8-month period, and it was more responsive to clinical ly significant changes in vision than was a generic health status meas ure tie, the Sickness Impact Profile).