Evaluation of the relationship between quality of vision and the visual function index in Japanese glaucoma patients

We compared two types of visual field index including mean deviation (MD) and the visual field index (VFI) for assessing the relationship between quality of life (QOL) and the loss of visual field in open-angle glaucoma patients. We examined 336 eyes of 168 consecutive glaucoma patients. All participants completed the Japanese version of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25). Visual field testing using the Humphrey Field Analyzer (HFA) was performed to obtain both MD and VFI in the bilateral eyes of each patient. We defined eyes of better MD or VFI as the better eye and the fellow eyes as the worse eye. Visual field data and scores of NEI VFQ-25 were compared between patients with normal tension glaucoma (NTG) and patients with primary open-angle glaucoma (POAG). A single linear regression analysis was applied to assess the significance of the relationship between QOL and visual field, and to compare the strength of correlations between MD and the VFI. An unpaired t test was used for the comparison the data between NTG and POAG. A significant relationship was observed between QOL and visual field in nine subscales and the composite in both the better eye and the worse eye. The relationship was stronger in the better eye than in the worse eye. The correlation coefficients of the VFI were slightly higher than those of MD overall. The highest correlation coefficients were demonstrated in ten subscales and the composite in the better eye of the VFI. Only the score for general vision was significantly higher in NTG patients than POAG patients. A significant relationship was found between QOL and both the VFI and MD, but the VFI had a marginally better correlation than that of MD. While QOL was better related with visual field loss in the better eye than in the worse eye, the difference was not large. Not much of a difference was found in the status of QOL between NTG patients and POAG patients.