Modeling the effects of vascular impairments on blood flow autoregulation in the retinal microcirculation

BrendanFry

Metropolitan State University of Denver

"Modeling the effects of vascular impairments on blood flow autoregulation in the retinal microcirculation"

The retinal microcirculation supplies blood and oxygen to the cells responsible for vision, and vascular impairments – including compromised flow regulation, reduced capillary density, and elevated intraocular pressure – are involved in the progression of eye diseases such as glaucoma. Here, an established theoretical model of a retinal microvascular network will be presented and extended to investigate the effects of these impairments on retinal blood flow and oxygenation as intraluminal pressure is varied. A heterogeneous description of the arterioles based on confocal microscopy images is combined with a compartmental representation of the downstream capillaries and venules. A Green’s function method is used to simulate oxygen transport in the arterioles, and a Krogh cylinder model is used in the capillary and venular compartments. Acute blood flow autoregulation is simulated in response to changes in pressure, shear stress, and metabolism. The model predicts that impaired flow regulation mechanisms, decreased capillary density, and increased intraocular pressure all cause a loss in the autoregulation plateau over the baseline range of intraluminal pressures (meaning that blood flow is not maintained constant over those pressures), leading to a corresponding decrease in oxygenation in that range. Small impairments in capillary density or intraocular pressure are predicted to mostly be offset by functional flow regulation; however, larger changes and/or combinations of vascular impairments lead to a significant decrease in oxygenation. Clinically, since poor retinal tissue oxygenation could lead to vision loss in advanced glaucoma, model results suggest early identification of vascular changes to prevent these impairments from progressing.
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