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Kirk Kohwa Hou, Adrian Au, David Sarraf; Evaluation of Pseudoflow Artifact with OCT Angiography. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2851. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Pseudoflow artifact is defined as flow signal detection with en face optical coherence tomography angiography (OCTA) in the absence of true motion. The aim of this study is to determine the cause of pseudoflow artifact in eyes with macular exudates due to diabetic macular edema and retinal vein occlusion.
This study is a retrospective review of 20 eyes with hard exudates due to diabetic macular edema or retinal vein occlusion evaluated with OCTA at the Stein Eye Institute UCLA. Eyes with macular exudates as noted with cross sectional and en face OCT were identified. Corresponding OCTA images (3 x 3 MM and 6 x 6 MM) were analyzed for the presence of pseudoflow and analysis was performed to determine the cause and mechanism of this OCTA artifact.
19/20 eyes with hard exudates illustrated corresponding pseudoflow signals with en face OCTA. The OCTA signals were bright on the en face projection with a corresponding flow signal displayed with the cross sectional B scan overlay. Of note, all cases of hard exudates with pseudoflow signals displayed corresponding true flow signals in the superficial retinal layers immediately above the exudates implicating projection as the source of the pseudoflow signal. Further, 11/20 eyes demonstrated hard exudates without pseudo-flow signals. In all cases, these lesions were found in the foveal avascular zone or in areas of capillary dropout. Also, 3/20 eyes demonstrated large cystic cavities of lipid exudation with corresponding pseudoflow signals which did not correspond with overlying true flow signals likely corresponding to scattered suspended particles in motion or SSPIM.
Our results suggest that pseudoflow signals generated by hard exudates are due to projection artifact. Notably, hard exudates often resemble the flow pattern of the overlying superficial capillary plexus. Furthermore, hard exudates do not exhibit pseudoflow signal when located in areas without overlying vasculature such as the FAZ or areas of capillary dropout. We suspect that hard exudates reflect de-correlated signal from the overlying vessels providing a highly reflective substrate for the appearance of projection artifact. We further identified cystic cavities of lipid exudation consistent with SSPIM suggesting that these lesions are pathologically different from focal hard exudates and may exhibit Brownian motion of suspended lipid.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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