Cost-effectiveness analysis in glaucoma: what drives utility? Results from a pilot study in Sweden.

Purpose: To investigate the effect of different levels of visual field defect in glaucoma on utilities and to test if utilities could be assessed using a general questionnaire such as the EQ-5D.
Methods: A cross-sectional study in 199 patients with ocular hypertension or open-angle glaucoma grouped into 5 severity stages according to visual field defects was performed in 4 specialized ophthalmic centres. Descriptive analysis was performed for the sample and by stage, and the effect of vision loss on utility was investigated with multiple step-wise regression analysis.
Results: The mean age of the sample was 70 and the mean MD in the worse eye was -13.1 dB (SD 10.2). Visual acuity (VA) was 0.63 and 0.87 in the worse and better eye, respectively, and the mean utility was 0.80 (SD 0.23). Utility decreased with increasing glaucomatous damage, ranging from 0.84 for mild disease to 0.72 for severe damage (MD -2.5 to -28.1), but the difference between the groups was not statistically significant when controlling for co-morbidity, except for the most severe stage (p < 0.01). In multiple regression analysis, visual field in the better eye was significantly correlated with utility, and there was an indirect correlation between visual field in the worse eye and utility: the effect of total VA on utility was significant, and MD in the worse eye was correlated with total VA.
Conclusions: Utility is strongly correlated with overall vision. Our results suggest a relationship between glaucomatous damage and utility, and patients with severe damage have a significantly lower utility. However, this should be further investigated in larger samples that include more patients with moderate-severe bilateral damage.