Automated selection of major arteries and veins for measurement of arteriolar-to-venular diameter ratio on retinal fundus images.

An automated method for measurement of arteriolar-to-venular diameter ratio (AVR) is presented. The method includes optic disc segmentation for the determination of the AVR measurement zone, retinal vessel segmentation, vessel classification into arteries and veins, selection of major vessel pairs, and measurement of AVRs. The sensitivity for the major vessels in the measurement zone was 87%, while 93% of them were classified correctly into arteries or veins. In 36 out of 40 vessel pairs, at least parts of the paired vessels were correctly identified. Although the average error in the AVRs with respect to those based on the manual vessel segmentation results was 0.11, the average error in vessel diameter was less than 1 pixel. The proposed method may be useful for objective evaluation of AVRs and has a potential for detecting focal arteriolar narrowing on macula-centered screening fundus images.