Developing a heterogeneous model of the arteriolar vasculature in the human retina

Abstract

Purpose : This work adapts a previous heterogeneous model of the murine retinal vasculature to be relevant to human. Oximetry and structural data are used to translate the mouse model into a human model that can predict blood flow and tissue oxygenation in the retinal arterial architecture.

Methods : A theoretical model of the human retina is extrapolated from a previous mouse model based on confocal microscopy images. The vasculature is represented as a directed graph where each edge corresponds to a blood vessel with a specific diameter and length. Oximetry data from the human retina are used to convert the murine vascular network to a human network by adapting: (i) the number of main arterial branches and the angles between them, (ii) vessel diameters, and (iii) vessel lengths. In the human model, oxygen levels in the retinal arterioles and surrounding tissue are calculated using Green’s functions. Blood flow, pressure, and viscosity are also computed.

Results : A scaling factor of 3.6 was used to convert murine diameters to human values based on data averaged from five experimental studies. A mouse-to-man scaling factor of 5.4 for vessel length was obtained based on oximetry images and position of the fovea. Figure 1A shows the predicted values of blood flow along a particular vascular pathway of the human model. Figure 1B depicts the predicted levels of the partial pressure of oxygen (PO₂, in mmHg) throughout the human arteriolar network. The arteriolar model is not connected to the downstream capillaries and venules, so the figure is a proof of principle but does not give precise levels of PO₂.

Conclusions : This study provides a mathematical model of the human retinal vasculature that can predict blood flow and oxygen levels within a spatially heterogeneous arteriolar network. The heterogeneous arrangement of arterioles in this model accounts for the complex geometry of blood vessels and diffusion of oxygen from multiple sources into one tissue point; however, it does not account for the oxygen supplied by the capillaries. This heterogeneous model of the retinal arterioles will be connected to a series of compartments representing the capillaries and veins to create a hybrid model description of the retinal microcirculation.

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1. Model predictions of flow (A) and partial pressure of oxygen (B) in the arteriolar network of the human eye.