Comparison of Rates of Change Between Binocular and Monocular Visual Fields

PURPOSE. To compare rates of change between binocular and monocular visual fields. METHODS. The study included 1264 visual fields from 62 normal-tension glaucoma patients with a minimum of nine pairs of visual fields for at least 5 years of follow-up. Integrated binocular visual fields (BVFs) were calculated from the two monocular visual fields using a binocular summation. Linear regression of mean deviation (MD) values was used to evaluate the rates of change of the BVFs and monocular visual fields. For each patient, the eye with the worse MD value at baseline was defined as the worse MD eye. The eye with the faster rate of change of monocular visual fields was defined as the faster-changing eye. RESULTS. The mean age of subjects was 61.8 years at baseline, the mean number of paired visual field tests was 10.2, and the mean follow-up was 8.1 years. The mean rate of change in the BVFs (-0.10 dB/y) was significantly slower than that of the faster-changing eyes (-0.34 dB/y) and faster than that of the slower-changing eyes (-0.06 dB/y; P < 0.001 for both comparisons). Forty-five eyes (64.5%) among the worse MD eyes at baseline were identified as faster-changing eyes at last follow-up, and having a worse MD value at baseline was a risk factor for being the faster-changing eye (P = 0.025). CONCLUSIONS. The rate of change in BVFs was intermediate between the rates of the fasterchanging and slower-changing eyes.