<p>Reference line “c” is a line from the center of the optic disc to the center of the macula. The vertical distance of the central vessel trunk “a” and horizontal distance “b” was measured from the reference line and retinal nerve fibre layer width (RNFLW) using Image J software. Inset shows the division of the disc by two lines into 4 quadrants for determining the exit quadrant of the central vessel trunk.</p
