Figure 5. Retinal vascular geometry parameters .

Retinal vascular tortuosity, retinal vascular branching angle and retinal vascular fractal dimension are shown. Tortuosity is derived from the integral of the curvature square along the path of the vessel, normalized by the total path length, which takes into account the bowing and points of inflection. Branching angle is defined as the first angle subtended between two daughter vessels at each bifurcation. Fractal dimension quantifies the complexity of the whole branching pattern of the retinal vascular tree and is defined as the gradient of logarithms of the number of boxes and the size the boxes.