Dark Signals in the Choroidal Vasculature on Optical Coherence Tomography Angiography: An Artefact or Not?

Figure 2

Orientation of vessels according to the type of scanning laser used. The inner and outer neuron layers and the inner and outer photoreceptor segments appear dark on both SD-OCT and OCTA because of the “coherence” of the scanning laser. Similarly, if blood flow is parallel to the orientation of the scanning laser, for example, in the optic disc region, it becomes dark on OCT and OCTA (red arrows and red dash-dotted boxes). OCTA: optical coherence tomography angiography; SD-OCT: spectral-domain optical coherence tomography.