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Moussa Zouache, Philip J Luthert, Ian Eames; Computational Model of the Oxygen Delivery to the Outer Retina Reveals Marked Heterogeneities in Oxygen Distribution. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4321.
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The choriocapillaris is a 10-30µm thick capillary bed located underneath the retina, which is solely responsible for the supply of oxygen to the photoreceptors. The blood flow through the choriocapillaris is remarkably high. A discrete lobular segmentation of the plexus is observed in the macula and the posterior fundus. Oxygen is delivered to the photoreceptors by diffusing from the choriocapillaris across the outer retina. The aim of this study was to investigate the oxygen delivery to the outer retina over the macular region and the posterior pole.
A computational model of a choriocapillary lobule informed by the angioarchitecture of the choriocapillaris as observed through whole mounts stained for Ulex Europaeus Agglutinin I, a vascular marker, was built and studied. Analytical and numerical solutions for the flow and oxygen transport were obtained. An experimental rheological model was built in order to validate the theoretical model. The model was then coupled with a model of the oxygen diffusion through the outer retina.
The computer model included the vascular volume fraction of the lobules, the spacing and distribution of arterioles and venules connecting with the plexus and the thickness of the different layers of the outer retina and derived parameters including the pressure and oxygen distribution. The model revealed marked heterogeneities in the oxygen distribution over the lobules, which resulted in a non-uniform repartition of the oxygen concentration in the outer retina.
The choriocapillaris exhibits significant heterogeneities in oxygen distribution that translates into a non-uniform distribution of the oxygen concentration in the outer retina. The size and distribution of the regions of minimal oxygen concentration are linked with the flow rate, the vascular volume fraction and the distribution of arterioles and venules in the choriocapillaris. Observations may have relevance for the pathogenesis of degenerative diseases and for the treatment of ischemic diseases. Furthermore, this model provides the basis for a more comprehensive model of the pathophysiology of the back of the eye.
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