Evaluation of minimum clinically meaningful changes in scores on the National Eye Institute Visual Function Questionnaire (NEI-VFQ) SST Report Number 19.

PURPOSE

To evaluate responsiveness of the National Eye Institute Visual Function Questionnaire (NEI-VFQ) to changes in visual acuity and to provide estimates of minimum clinically meaningful changes in NEI-VFQ scores.

METHODS

Data were combined from three clinical trials of submacular surgery for subfoveal choroidal neovascularization. Patients who completed NEI-VFQ interviews and visual acuity measurements at baseline and 2 years later contributed data for analysis. Data were analyzed using anchor-based (relating 2-year change in NEI-VFQ to 2-year change in visual acuity using correlation and linear regression) and distribution-based (standardized response mean) methods.

RESULTS

Of 1,015 patients enrolled, 828 patients completed NEI-VFQ interviews and had visual acuity measurements at baseline and 2 years later. Median age of patients was 75 years (range 18 to 94); all patients had subfoveal choroidal neovascularization in at least one eye. Median overall NEI-VFQ score at baseline was 69.9 (mean, 66.5). Based on anchor-based methods, a 2-line change in visual acuity of the better-seeing eye translated to a 3.4-point change in the overall NEI-VFQ score and from 2.4-point to 7.0-point changes in most subscale scores. The NEI-VFQ was sensitive to both gains and losses in visual acuity; the standardized response mean for the overall NEI-VFQ score in patients with a 2-line gain was 0.6 and for patients with 2-line loss was -0.3. In the subgroup of patients with a 2-line loss of visual acuity in the better-seeing eye, patients who had overall NEI-VFQ scores at baseline greater than the median (59.8) had an standardized response mean of -0.9 for the overall NEI-VFQ score and patients who had overall NEI-VFQ scores at baseline at or below the median had a standardized response mean of 0.2 for the overall NEI-VFQ score. A 4-point change in the overall NEI-VFQ and a 5-point change in individual subscale scores corresponded to a small clinically meaningful change.

CONCLUSIONS

The NEI-VFQ was responsive to 2-year changes in visual acuity but was less responsive to changes among patients with poorer NEI-VFQ scores at baseline. Based on this analysis, a 4-point change in the overall NEI-VFQ and a 5-point change in individual subscale scores may be considered minimum clinically meaningful within-person changes in NEI-VFQ scores.