Patients' perceptions of the value of current vision: assessment of preference values among patients with subfoveal choroidal neovascularization--The Submacular Surgery Trials Vision Preference Value Scale: SST Report No. 6

Abstract

Objective: To improve understanding and awareness of the impact of subfoveal choroidal neovascularization (CNV) on health-related quality of life, we sought to measure the preference value that patients with subfoveal CNV assigned to their health and vision status.

Patients and methods: Patients with subfoveal CNV completed telephone interviews about their quality of life prior to enrollment and random treatment assignment in the Submacular Surgery Trials, a set of multicenter randomized controlled trials evaluating outcomes of submacular surgery compared with observation. The interviewers asked patients to rate their current vision on a scale from 0 (completely blind) to 100 (perfect vision). The interviewers also asked them to rate complete blindness and then perfect vision, assuming their health otherwise was the same as it was at the time of the interview, on a scale from 0 (dead) to 100 (perfect health with perfect vision). Scores were converted to a 0 to 1 preference value scale for health and vision status, where 0 represents death and 1 represents perfect health and vision.

Results: Of 1015 participants enrolled in the Submacular Surgery Trials, 996 completed interviews that included the rating questions, and 792 (80%) answered all 3 rating questions in a manner permitting calculation of a single overall preference value for their current health and vision status on a scale from 0 (dead) to 1 (perfect). The mean preference value was 0.64 (median, 0.68; interquartile range, 0.51-0.80). The preference values correlated with age (Pearson correlation coefficient, -0.11; P = .002), patients' self-rated perception of overall health (Spearman correlation coefficient, 0.36; P<.001), and self-reported perception of vision (Spearman correlation coefficient, 0.47; P<.001). The preference values were significantly lower with poorer visual acuity in the better eye and greater evidence of dysfunction on either the Hospital Anxiety and Depression Scale or the Physical or Mental Component Summary scales of the Short Form-36 Health Survey but did not differ significantly by gender or other baseline characteristics such as race, treatment assignment, or size of the CNV lesion.

Conclusions: Vision loss from subfoveal CNV is associated with patient preference values that are as low as or lower than values previously reported for other serious medical conditions such as dialysis-dependent renal failure and AIDS, indicating that both unilateral and bilateral CNV have a profound impact on how patients feel about their overall health-related quality of life.

Figure 1

Conversion of ratings on a vision scale to a preference value on a scale from death to perfect health.

Figure 2

Relation of patient preference values for current vision and health (y-axis values) by National Eye Institute Visual Function Questionnaire (NEI-VFQ) ratings of eyesight (x-axis values) (Spearman correlation coefficient, 0.38; P<.001). For patient preference values, boxed areas show interquartile ranges, dots within boxes show means, lines within boxes show medians, and whiskers extending from box show 1.5 times the interquartile range. Circles beyond the whiskers are outliers. For the 4 individuals who reported themselves to be completely blind, the 4 points are plotted instead of showing a box and whisker plot.

Figure 3

Variables were grouped into 4 categories for multivariate analyses: demographic characteristics, clinical features, comorbid conditions, and quality of life. Each variable was evaluated alone for its relation to the preference value (shaded boxes). Statistically significant variables were then combined to form the best multivariate model (white boxes and arrows in third column) for each category. Once the best demographic model was picked, the best clinical model variables were added. Once the best demographic and clinical model was picked, the best comorbid conditions model was added. Quality of life variables were kept separate by instrument and were then added to the best demographic, clinical, and comorbid model. Asterisks (*) denote statistically significant variables. HADS-Anx indicates Hospital Anxiety and Depression Scale classification of anxiety; HADS-Dep, Hospital Anxiety and Depression Scale classification of depression; NEI-VFQ, National Eye Institute Visual Function Questionnaire; SF-36-MCS, Short-Form 36 Mental Component Summary Scale; and SF-36-PCS, Short-Form 36 Physical Component Summary Scale.