Fig. 5.

(a) Geometric drawing showing how velocity axial projection and cross-sectional area depend on vessel angle. (b, c) For relative flow determined in the B-mode plane, the velocity axial projection and vessel area change in the same direction when the vessel angle changes due to a 100-μm transverse shift. However, for relative flow determined in the en face plane (d, e), the velocity axial projection and vessel area change in opposite directions. Due to this counterbalancing effect, relative en face flow had a standard deviation of 10%, whereas relative B-mode flow had a standard deviation of 28% for a transverse shift of 100 μm near the optic nerve head ($N=\text{five vessels}$). Color-coded boxes are used to designate the same vessels in different planes.