A Computational Model of Peripheral Photocoagulation for the Prevention of Progressive Diabetic Capillary Occlusion

Figure 1

Pattern of capillary loss without burns. Normal condition of peripheral retina without photocoagulation. (a) (left) A 2D view of the configuration of the retinal capillary network, Mueller cells and other retinal cells in the in silico peripheral retina. Size of a Mueller cell (green) is 24 μm [39]. Size of other retinal cells (olive) is 21 μm. Diameter of arteriole (red) is 20 μm. Diameter of venules (red) is 25 μm. Diameter of shunting vessels at the top of the model area (red) is 18 μm. Capillary (red) diameter is 10 μm. Vessel pattern and diameters are from [25]. (Middle) flow velocity map of the vascular network. Capillaries carry blood flow with smaller velocities than arterioles, venules, and shunting vessels. (Right) oxygen tension map of the modelled section. Cells in the proximity of vessels have relatively higher oxygenation and redder colors than those located at a greater distance but no area is ischemic in the normal condition. (b) Evolution of the flow velocity map following initial capillary occlusion without photocoagulation. (Left) flow map shows closure of a capillary in AV sector. (Middle and right) a cascade of capillary occlusion instances propagates anteriorly and posteriorly within the same sector, and therefore the flow map shows a progressively larger gap. Color bar has units μm/s. Warmer color represents greater flow velocity. (c) Evolution of the oxygen tension map following initial capillary occlusion without photocoagulation. (Left) oxygen tension map shows a group of poorly oxygenated cells near occluded vessel. (Middle and right) area of the ischemic region expands in response to the increasing number of derived capillary occlusion instances. Also oxygen tension in the venules drops with time. Color bar has unit mmHg. Warmer color represents higher oxygen tension.

(a) Initial states

(b) Flow map

(c) Oxygen tension