Influence of posture on the visual field in glaucoma patients and controls

The intra-ocular pressure rises when body position is changed from sitting to supine. This phenomenon occurs to the same extent in healthy people and glaucoma patients. The purpose of this preliminary study was to determine the effect of posture on the visual field. Visual fields of 15 eyes of 12 normal-tension glaucoma (NTG) patients, 16 eyes of 11 high-tension glaucoma (HTG) patients and 30 eyes of 26 healthy controls were measured in the upright and supine positions with program G1X on an Octopus swivel-arm perimeter. The delta mean defect (delta MD), that is MDupright-MDsupine, was calculated for each patient and compared among study groups. Whereas visual fields improved in healthy controls (delta MD = +0.45 dB), glaucoma patients showed a slight deterioration of the visual field after changing position from supine to upright (HTG: delta MD = -0.25 dB, NTG: delta MD = -0.24 dB). The difference between HTG and controls, as well as between NTG and controls, was statistically significant (p < 0.002, Student's t test). These findings indicate that in some glaucoma patients the regulatory mechanisms for blood supply in the optic nerve head are insufficient.