Differences in Blood Flow Between Superior and Inferior Retinal Hemispheres

To determine whether the blood flow in the superior retina is significantly different from that in the inferior retina, and to determine whether the posture affects the blood flow in the superior and inferior retina. The blood flow in the vessels around the optic nerve head was measured by laser speckle flowgraphy in the sitting position in 68 healthy subjects. The blood flow in the superior peripapillary retina was compared with that in the inferior peripapillary retina. The measurements of the blood flow were performed in the sitting position, and the effect of switching to a supine position was determined at 2, 4, 6, 8, 10, and 30 minutes after the switch. The total relative flow volume (RFV)-all, RFV-artery, and RFV-vein were significantly greater in the superior retina than in the inferior retina (all P < 0.001). The mean diameter-all and mean diameter-artery in the superior retina were significantly larger than that in the inferior retina (all P < 0.05). The mean blur rate (MBR)-all, MBR-artery, and MBR-vein in the superior retina were also greater than that in the inferior retina (P < 0.001, P < 0.01, and P < 0.001, respectively). Although the ocular perfusion pressure was significantly changed with the postural alteration, the total RFV-all remained greater in the superior retina than in the inferior retina after the postural change. Clinicians need to be aware of the differences in the blood flow between the superior and inferior retinal peripapillary area when considering the mechanisms of retinochoroidal diseases.