Figure 2.

Definition of the retinal vessel geometric variables. Yellow lines are traced retinal vessels, and blue lines, arrows and titles are drawn to explain the math used to define the geometric variables. D ₀ = parent vessel diameter (μm), D ₁ = diameter of daughter vessel one (μm), D ₂ = diameter of daughter vessel two (μm), θ ₁ = angle between daughter vessel one and imaginary progress of parent vessel if no branching had occurred (degree), θ ₂ = angle between daughter vessel two and imaginary progress of parent vessel if no branching had occurred (degree), L = strait line from branching point to branching point, length diameter ratio = L/D ₀, branching angle = θ ₁₊ θ ₂, branching coefficient = ${(D_1+D_2)}^2/d_0^2$, junctional exponent deviation $\left({(D_0^3-D_1^3-D_2^3)}^{1/3}\right)/D_0$.