Abstract
PurposeTo characterize the choriocapillaris (CC) structure in relation to subretinal fluid (SRF) as a possible systematic error source using spectral domain (SD-OCTA) compared to swept-source optical coherence tomography angiography (SS-OCTA).MethodsThis is a prospective case-control study of 23 eyes. Ten patients with acute central serous chorioretinopathy (CSC), three patients with partial macular-off retinal detachment (RD) and ten healthy, age-matched controls were included. Abnormal CC decorrelation signals were quantitatively compared in CSC and controls by means of custom image processing. To investigate the influence of SRF on CC OCTA signal, the extent of SRF was quantified with a macular heatmap and compared with the corresponding OCTA signal of the CC.ResultsSS-OCTA yielded a more homogeneous OCTA signal from the CC than SD-OCTA, offering less signal dispersion and variability in healthy and diseased eyes. Both devices demonstrated CC signal voids in CSC and RD, respectively. In CCS, the voids were predominantly located in the area with SRF. Compared to SD-OCTA, SS-OCTA delivered a more homogenous OCTA signal and reduced signal voids in the CC underneath SRF in both RD and CSC (CSC, 7.6% ± 6.3% vs, 19.7% ± 9.6%, p < 0.01). Despite this significant attenuation of signal voids, SS-OCTA continued to reveal signal voids below SRF and more pixels with reduced OCTA signals in CSC patients compared to controls (7.6% ± 6.3%, 0.1% ± 0.1%, p < 0.0001).ConclusionUnderstanding OCTA artifacts is critical to ensure accurate clinical evaluations. In this study, we describe the presence of SRF as an important shadow-causing artifact source for CC OCTA analysis which can be mitigated but not completely eliminated by employing SS-OCTA.
Highlights
The choriocapillaris (CC) is a few-lm-thin layer of capillaries of relatively large diameter located in the inner aspect of the choroid below the retinal pigmented epithelium (RPE) [1]
We describe the presence of subretinal fluid (SRF) as an important shadow-causing artifact source when assessing the CC—one that can be mitigated but not completely eliminated when employing swept-source optical coherence tomography angiography (OCTA)
We show that SRF is associated with a diseaseindependent, reduced SD-OCTA signal from the CC by examining patients with acute central serous chorioretinopathy (CSC) and retinal detachment (RD)
Summary
The choriocapillaris (CC) is a few-lm-thin layer of capillaries of relatively large diameter located in the inner aspect of the choroid below the retinal pigmented epithelium (RPE) [1]. OCTA technology employs motion contrast to image blood flow and thereby vessels through different segmented areas in the eye, eliminating the need for intravascular dyes. The newer generations, on the other hand, apply swept-source OCT (SS-OCT) technology, which uses a longer wavelength of nearly 1050 nm (compared to 840 nm in SD-OCT) and a higher scan speed of 100,000 A-scans/s (compared to 68,000 A-scans/s). It allows deeper penetration into the tissue of 3 mm (compared to 2 mm), with the compromise of a slightly lower axial resolution of 6,3 lm (compared to 5 lm, personal communication with Zeiss)
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