A Novel Approach to Measuring Binocular Visual Fields in Glaucoma

Precis: Combined average visual field index (VFI) is a simple, novel tool for binocular visual field which agrees with the existing binocular integrated visual field (IVF) model, as well as patient reported activity limitation in glaucoma. Purpose: The aim was to determine the correlation between novel models of binocular visual field with the existing IVF and glaucoma activity limitation (GAL-9). Materials and Methods: IVFs were calculated from the monocular visual fields of 58 patients with primary glaucoma and the novel binocular visual field models termed binocular summation visual field index (BiSumVFI) and combined average visual field index (CaVFI) were derived from the VFIs of both fields. GAL-9 questionnaire was administered to the patients. The relationship between IVF and the 2 newer models of binocular fields were determined and the correlation of IVF, BiSumVFI, and CaVFI with GAL-9 was estimated. Results: A very strong correlation was seen between IVF and BiSumVFI (r=-0.913, P<0.001, confidence interval: -0.958 to -0.821) and also between IVF and CaVFI (r=-0.896, P<0.001, confidence interval: -0.947 to -0.802). Linear regression analysis showed a significant R (2) of 0.902 (P<0.001) to predict IVF from BiSumVFI and R (2) of 0.847 (P<0.001) to predict IVF from CaVFI. IVF, BiSumVFI, and CaVFI correlated moderately and significantly with GAL-9 with correlation coefficients of 0.481, -0.499, and -0.505, respectively. Conclusion: The binocular summation VFI and combined average VFI models of binocular visual field are good predictors of IVF in glaucoma. They correlate well with the existing IVF model in estimating patients' perception of activity limitation in glaucoma.