Review Article
Dark Signals in the Choroidal Vasculature on Optical Coherence Tomography Angiography: An Artefact or Not?
Figure 1
Increased penetration depth of scanning laser in a case of retinal pigment epithelium atrophy. (a) Multicolour images showed a round subfoveal atrophic RPE lesion. (b) SD-OCT shows collapse of the outer retina, atrophy of the choroidal capillaries and RPE, and increased penetration (the inserted image indicates the orientation of OCT scanning). (c) Cross-sectional OCTA at the same location shown in (b) confirms atrophy of the choroidal capillaries and enhances signals in the deep choroidal vasculature (red dash-dotted box). (d) En face OCTA shows a choroidal vessel that is dark because of the masking effect of the RPE and choroidal capillaries (red arrow). (e) An infrared image confirms that the transition between light and dark vascular signal is at the atrophy margin. (f) Cross-sectional OCTA shows a corresponding hypointense halo (red arrow). (g) En face OCTA of another case showing a hypointense halo in the atrophic region with hyperreflective vascular signals. (h) Corresponding cross-sectional OCTA confirming the hyporeflective halo without masked effect, which needs to be explained by other mechanisms. OCTA: optical coherence tomography angiography; RPE: retinal pigment epithelium; SD-OCT: spectral-domain optical coherence tomography.
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