Visual impairment and vision-related quality of life in the Early Manifest Glaucoma Trial after 20 years of follow-up

Abstract

Purpose To determine the association between vision-related quality of life (VRQOL) and levels of visual function loss in the Early Manifest Glaucoma Trial (EMGT). Methods Two hundred and fifty-five patients were included in the EMGT between 1993 and 1997 and followed regularly by ophthalmic examinations. A Swedish translation of the National Eye Institute Visual Function Questionnaire 25 (NEI VFQ-25) was self-administered at several follow-up visits until 2014. We analysed the association between Rasch-calibrated NEI VFQ-25 scores and visual function in the best eye at the final follow-up visit. Results Ninety-one per cent (233/255) of all participants completed the NEI VFQ-25 at least once. In univariate logistic regression analysis, NEI VFQ-25 scores were modestly associated with visual acuity (VA) (r2 = 0.330, p < 0.001), visual field index (VFI) (r2 = 0.200, p < 0.001) and perimetric mean deviation (MD) (r2 = 0.193, p < 0.001). In multivariate analysis, VA and VFI together accounted for approximately 40% (r2 = 0.380) of the NEI VFQ-25 scores. NEI VFQ-25 scores were significantly higher for patients with no visual impairment (mean 73 ± 22) than for visually impaired patients (mean 31 ± 15, p < 0.001). VFI worse than 50% or MD worse than -18 dB was significantly associated with low VRQOL scores (p < 0.001). Conclusions Our results support the widespread, albeit arbitrary, use of a better-eye visual field of <50% as an important threshold for a significant reduction in VRQOL.