Abstract
To investigate the correlation between posterior pole choroidal blood flow evaluated with digital subtraction indocyanine green angiography and enface optical coherence tomography angiography (OCTA). Imaging in animal study. The anatomy of 2 cynomogulus monkeys was studied. Each monkey was given a 0.75 mg/kg injection of indocyanine green in the saphenous vein. The dynamic angiographic filling sequence was recorded at 15 frames per second using the Heidelberg Spectralis. After image registration, sequential frame subtraction was used to image the dye front moving through the choroid. The OCTA was obtained by frame averaging nine separate choriocapillaris slab flow images obtained from the Zeiss Plex Elite 9000. Posterior pole choriocapillaris filling pattern in relation to the choriocapillaris anatomy as imaged by OCTA. In the posterior pole, the choriocapillaris fills in the pattern of discrete units with variable sizes and shapes. The cycle of dye filling begins in the peripapillary area and progresses toward the periphery in a wavelike manner. This filling pattern repeats in a cyclical manner, consistent with the cardiac cycle. OCTA shows a uniform mesh of vessels. While OCTA shows a uniform meshwork appearance of the choriocapillaris, the dynamic dye angiography suggests an irregular configuration of functional units partitioned by pressure gradients as opposed to structural boundaries. Disturbance of local perfusion pressure within choroidal vasculature may result in abnormal flow patterns, which could be evaluated in the clinic using commercially available equipment.
Highlights
To investigate the correlation between posterior pole choroidal blood flow evaluated with digital subtraction indocyanine green angiography and enface optical coherence tomography angiography (OCTA)
Advances in digital indocyanine green angiography (ICGA) have permitted high speed angiography and digital subtraction of sequential frames as a means of following the dye front of the dye bolus, without the need or potential artefacts caused by increasing the intraocular p ressure[11]
After dye first entered the macular area of choriocapillaris in regions around the optic disc and posterior pole (Figs. 2A, 3A), an irregular segmented pattern can be seen as the choriocapillaris fills in discrete units starting in the peripapillary area and progressed radially to the macular region (Figs. 2B, C, 3B, C)
Summary
To investigate the correlation between posterior pole choroidal blood flow evaluated with digital subtraction indocyanine green angiography and enface optical coherence tomography angiography (OCTA). Hayreh surmised the choriocapillaris filled in a lobular pattern and proposed each lobule was surrounded by a venous collecting channel that cumulated the blood from the lobule. Flower captured ICGA images using a specially modified fundus camera and prepared subtraction angiography to study choriocapillaris filling and compared with corrosion casts from rhesus m onkeys[3]. They concluded that the choriocapillaris appeared as a uniform plexus capillary vessels lying in a plane, whose feeding and draining vessels enter from below[9]. We correlated the in vivo OCTA images of the choriocapillaris with flow dynamics extracted using subtraction of ICGA in monkeys
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