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Ji Eun E Lee, Keun Heung Park, Kang Yeun Pak, Hak Jin Kim, Ik Soo Byon, Sung Who Park; Functional end-arterial circulation of the choroid assessed using fat embolism and electric circuit simulation. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4653.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the choroidal circulation using fat embolism model and electric circuit simulation.
Experimental fat embolism was induced by infusing triolein emulsion into the intracarotid artery in cats. Video fluorescein angiography (FA) was recorded. The observations were interpreted using a custom software which was developed to simulate the choriocapillaris as a schematic electric circuit; blood flow as electric current, intravascular pressure as voltage and vascular resistance as electric resistance. Dual layered hexagons representing the choriocapillaris lobules were arranged to represent the choriocapillary bed. An anode and cathodes were connected to the center and periphery of each hexagon representing the terminal arteriole and draining venules, respectively. Disconnecting anodes from the circuit simulated choroidal embolism.
Fat embolism model induced perfusion defects in two categories. In the scatter perfusion defects suggesting an embolism at the terminal arterioles, fluorescein filling from the perfused lobule to the adjacent non-perfused lobule was observed. In the segmental perfusion defects suggesting occlusion of the posterior ciliary arteries (PCAs), the hypo-fluorescent segment became perfused by spontaneous resolution of embolism, but subsequent non-perfusion of smaller segments was not observed. The angiographic findings could be simulated using electric circuit. Although electric currents formed to the disconnected hexagon, they were at very low level compared to the connected. As resistance of the collector venule decreases, currents in the connected hexagon increases, while in the disconnected decreases.
The choroid appeared to be composed of multiple sectors having no anastomosis to other sectors, but its own anastomotic arterioles in each sector. The choriocapillaris has a continuous vascular bed, but blood flows in an end-arterial nature following a pressure gradient due to drainage through the collector venule. Occlusion of the terminal arteriole or PCA results in a lobular or sectorial infarction, as flows from the adjacent perfused lobules are much less than normal perfusion.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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