Swept - Source Optical Coherence Tomography Angiogaphy Imagi
A Study was conducted to analyze the swept-source optical coherence angiography images acquired at different depths above and below the default location of the Zeiss PLEX Elite 9000.

Normal eyes of subjects in their 20s and 30s were evaluated. Angiographic slab images were taken at the default location of 29 microm to 49 microm below the retinal pigment epithelium and 21 microm to 41 microm through 52 microm to 72 microm below in steps. The images were processed using the projection removal function from the device's software. Raw images were evaluated, as were images that underwent a published compensation technique that adjusts for light penetration to the sampled layer.

Results:
--11 eyes of 11 subjects were evaluated for the uncompensated and the compensated sets with the projection removal function turned off and on.

--The default location, 29 µm to 49 µm below the retinal pigment epithelium, showed a granular choriocapillaris appearance.

--This appearance remained in all slabs from each group, differing slightly throughout depth.

--The projection removal function modified the grayscale values and diminished projection from overlaying retinal vessels.

--The compensation technique altered the appearance of flow deficits, and the changes induced by it were more evident on the images were the projection removal function was turned on.

Flow images of the choriocapillars are similar in appearance in swept-source angiography of the optical coherence from different levels and show projection from the choriocapillaris to be important in the formation of the picture, although layers of vessels in internal choroid may contribute by different quantities. A model is proposed which explains the substantial projection artifacts reported in the choroid with the angiography of swept source.

Source: https://journals.lww.com/retinajournal/Abstract/2021/07000/SWEPT_SOURCE_OPTICAL_COHERENCE_TOMOGRAPHY.3.aspx
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