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Moussa Zouache, Ian Eames, Christian A Klettner, Philip J Luthert; Computational analysis of the impact of a reduction of the blood flow in large choroidal arteries on the function of the choriocapillaris.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4628. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The choriocapillaris, which forms the inner layer of the choroidal vasculature, is responsible for sustaining the photoreceptors and clearing waste products originating from the outer retina. A decrease in blood flow velocities has been reported in large choroidal arteries in the early stages of Age-related Macular Degeneration (AMD); however, it is not clear how these changes affect the function of the choriocapillaris. In the present study, we investigate the impact of a reduction of the blood supply to the choriocapillaris on the delivery of metabolites to the outer retina and the clearance of waste material, using a computational approach.
The computational analysis was carried out using a previously established model of the choriocapillaris, which was informed by the angioarchitecture of the human choroid as observed through whole mounts stained with Ulex Europaeus Agglutinin I, a vascular marker. Analytical and numerical solutions for the blood flow and mass transport in the choriocapillaris were obtained. These were then paired with a model for mass exchange between the choriocapillaris and the retina.
The computer model included the vascular volume fraction of the choriocapillaris, the spacing and distribution of arterioles and venules connecting with the plexus and mass exchange process rates with the outer retina based on data collected from the literature; extracted parameters included blood pressure drop, blood travel time and mass extraction and clearance rates. The model revealed that a decrease in the blood supply to the choriocapillaris resulted in a marked increase in the heterogeneity of both mass extraction and clearance rates over the capillary bed. The mass extraction and clearance rates were also found to vary non-linearly with changes in arterial flow rates, and to display a strong dependence on the diffusivity of the substance considered.
Reductions in arterial supply to the choriocapillaris have a non-linear and substance-specific impact on both average mass extraction and clearance rates. The significance of the non-linearity is that the clearance of substances that diffuse slowly across the capillary wall will be dramatically compromised by a decrease in the blood supply to the choriocapillaris. This finding may have significance for the clearance of sub-retinal pigment epithelium material in AMD.
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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