Figure 3.

(A) Schematic diagram showing the first bifurcation point of the superior and inferior arterioles originating from the optic disk, considered during tortuosity, radius of curvature, and curvature measurement. (B) Clinically, two lines crossing vertically through the center of the optic disk, one from 12 o’clock to 6 o’clock and the other from 3 o’clock to 9 o’clock, were taken to define the four quadrants clockwise, namely, superior nasal (1), superior temporal (2), inferior temporal (3) and inferior nasal (4).

Notes: (A) Reproduced from Mazumder AG, Sharma UR, Aishwaryaprajna, Nawn D, Chakraborty D, Chatterjee J. Extracting arteriolar geometric attributes (tortuosity index, curvature, bifurcation angles) in normal and diabetic colour fundus images-a preliminary report. Current Indian Eye Research. 2015; Dec 2015:86–87.⁵⁰