Fig. 20.

Demonstration showing how OCTA projection artifacts are generated. (A–C) Water is flowing in the clear channel and in repeated images over time, are seen as a region of variable reflections. However, the light transmitted through the water illuminates the background and the illumination also changes over time. The variance (D) of the images can be computed to show motion contrast. The changing background illumination is detected even though the background itself is not moving. Similarly, flowing blood cells can generate motion contrast for stationary structures which are below them. (From Spaide et al., 2015a).