![]() While prior studies have improved the understanding of the general properties of blood flow in the inner choroid, the extent to which these findings are valid in anatomically realistic human choroidal vasculature is unknown. In these geometries, blood is supplied and drained by cylindrical and regularly spaced arterioles and venules 23, 24, respectively. The choriocapillaris has previously been treated as a thin plane of uniform thickness interrupted by intercapillary pillars modeled either as uniform cylinders 23, porous media 24, or an open plane 25, 26. ![]() Given observations of choroidal microvascular anatomic changes in aging and in retinal diseases in cadaver eyes, coupled with those from functional perfusion imaging in living patients, we and others have sought to connect these two domains of knowledge by understanding the relationship between microvascular anatomy and inner choroidal blood flow.Įfforts to describe inner choroidal hemodynamics have applied fluid dynamics principles. Indeed, emerging evidence suggests that such perfusion alterations also extend beyond the margins of retinal atrophy and may predict disease progression 17, 18, 19, 20, 21, 22. These histopathologic observations have been supported by functional imaging of choroidal perfusion via indocyanine green angiography (ICGA), optical coherence tomography angiography (OCTA), and laser Doppler flowmetry (LDF), which have detected alterations in choroidal blood flow rate 12, 13, 14 and focal hypoperfusion 15, 16 in patients with AMD. ![]() For example, histopathologic analyses of human donor eyes reveals loss of capillary density and diameter in AMD 8, 9, 10, and capillary involution that may extend beyond the margin of retinal death in late AMD 11. Vascular remodelling of the choroid through neovascularization or atrophy is a common etiologic element of numerous blinding ocular conditions, including age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma. Failure of the choroid to fulfil its diverse functions can contribute to retinal disease. Beyond metabolic transport, the choroid is also responsible for, among other functions, trafficking of circulating and resident inflammatory cells to sites of infection, damage, or disease of the outer retina 2, 3, 4, 5, 6, 7. Because phototransduction and the visual cycle are extremely metabolically demanding, the arterioles of the macular choroid subsume among the greatest blood flow of the entire body per unit mass 1. The inner choroid is comprised of arterioles and venules from Sattler’s layer that feed and drain the choriocapillaris, which is a highly anastomotic planar capillary bed. The choroid is an anatomically unique vascular network that supports the nutrient exchange of the photoreceptor and retinal pigmented epithelial (RPE) layers of the retina. These first-ever findings improve understanding of how choroidal anatomy affects hemodynamics and may contribute to pathogenesis of retinal diseases such as AMD. ![]() Reductions in capillary, arteriolar, and venular density not only reduce the overall blood velocity within choriocapillaris, but also substantially increase its spatial heterogeneity. Here, we demonstrate that anatomic parameters, including arteriolar and venular arrangements and intercapillary pillar density and distribution exert profound influences on inner choroidal hemodynamic characteristics. We subjected image-based inner choroid reconstructions from eight human donor eyes to ICH simulation using a kinetic-based volumetric lattice Boltzmann method to compute hemodynamic distributions of velocity, pressure, and endothelial shear stress. Therefore, we sought to understand the influences of choroidal microvascular architecture on the spatial distribution of hemodynamic parameters in choriocapillaris from human donor eyes using image-based computational hemodynamic (ICH) simulations. However, how inner choroidal anatomy affects hemodynamic perfusion is not well understood. Evidence from histopathology and clinical imaging suggest that choroidal anatomy and hemodynamic perfusion are among the earliest changes in retinal diseases such as age-related macular degeneration (AMD).
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