What Can Be Observed?

Blood flow within retinal vessels and retinal tissue blood flow can be observed as a two-dimensional map. Areas with faster blood flow are displayed in red tones, while areas with slower blood flow are displayed in blue tones. At present, it is not possible to display blood flow as absolute values such as millimeters per second; however, comparisons such as a certain percentage decrease relative to surrounding areas, normal sites, or previous measurements are fully feasible. Blood flow maps are displayed continuously at 30 frames per second, so blood flow variations due to heartbeat in arterial vessels can also be observed. Blood flow can be imaged within an area of approximately several millimeters square on the fundus. Even if the measurement site shifts due to fixation movement, since a wide area is originally being observed, measurement can continue until the area moves out of the field of view, so data is not wasted. Although the measurement site shifting may seem inconvenient at first glance, software has been developed to semi-automatically stitch these maps together, enabling measurement of an even wider area at once. Although not as clear as retinal vessels, choroidal blood flow maps can also be observed quite well.