Imaging the Deep Choroidal Vasculature Using Spectral Domain and Swept Source Optical Coherence Tomography Angiography

Abstract

Purpose To evaluate the deeper choroidal vasculature in eyes with various ocular disorders using spectral domain (SD) optical coherence tomography angiography (OCTA) and swept source (SS) OCTA. Methods Patients underwent OCTA imaging with either SD-OCTA (Zeiss Cirrus Angioplex or Optovue AngioVue) or SS-OCTA (Topcon Triton). Retinal pigment epithelium (RPE) integrity, structural visualization of deep choroidal vessels on en face imaging, and OCTA of deep choroidal blood flow signal were analyzed. Choroidal blood flow was deemed present if deeper choroidal vessels appeared bright after appropriate segmentation. Results Structural visualization of choroidal vessels was feasible in all eyes by en face imaging. In both SD-OCTA and SS-OCTA, choroidal blood flow signal was present in all eyes with overlying RPE atrophy (100% of eyes with RPE atrophy, 28.6% of all imaged eyes, P < .001). Conclusions While choroidal vessels can be visualized anatomically in all eyes by en face imaging, choroidal blood flow detection in deep choroidal vessel is largely restricted to areas with overlying RPE atrophy. Intact RPE acts as a barrier for reliable detection of choroidal flow using current OCTA technology, inhibiting evaluation of flow in deeper choroidal vessels in most eyes.

Visualization of deep choroidal vasculatures and measurement of choroidal vascular density: a swept-source optical coherence tomography angiography approach

“…There had been an impression that OCTA might not be suitable for imaging the choroid beneath choriocapillaris. According to Diaz et al, motion contrast signals produced bright vessel outlines only in areas with overlying RPE atrophy, and dark signals beneath intact RPE was deemed as absence of blood flow [8]. According to our study, within a range of choroidal depths, dark signals in OCTA images corresponded to vessel lumen in OCT B-scan, and deep choroidal vessels manifested as dark stripes in OCTA images.…”

“…Optical coherence tomography angiography (OCTA), widely used for non-invasive imaging of retinal and choriocapillary microvasculatures [6,7], has long been doubted for its value in deep choroid imaging. According to a previous report by Diaz et al [8], intact retinal pigment epithelium (RPE) was regarded as a barrier for reliable detection of choroidal blood flow with OCTA. One previous study employed RTVue OCTA device for the quantification of deep choroidal vasculatures [9].…”

Fractal Dimension Analysis of Widefield Choroidal Vasculature as Predictor of Stage of Macular Degeneration

“…Devices have been shown to be inconsistent in segmenting the choroid, except in areas of absent RPE. 9 Second, OCTA at present is limited with regard to the detection of flow within individual choriocapillaris vessels, as well as within deeper choroidal vessels. 1 The long wavelength of ICG cyanescence penetrates the RPE to provide high-resolution imaging of the choroidal vasculature.…”

Discordant vascular parameter measurements in diabetic and non-diabetic eyes detected by different optical coherence tomography angiography devices

“…However, both machines have been reported to have difficulty visualizing choroidal vessels due to the overlying RPE. [33] Given these limitations, we elected to use FV as a proxy to evaluate choroidal blood flow since it does not require clear visualization of vessels. [3,19]…”