Zero-crossing interval correction in tracing eye-fundus blood vessels

Abstract

We are developing a health screening system for color eye-fundus photography. The system is designed to detect the first signs of adult diseases, for which purpose it is important to detect and trace eye blood vessels. This paper describes a method of finding the papilla by Hough transform, and from there tracing blood vessels by a second-order derivative Gaussian filter. The width of the blood vessel is obtained as the zero-crossing interval of the filter output. The filter is adjustable to the current width of the blood vessel being traced. In this process, since the obtained zero-crossing interval is larger than the true width of an ideal step-wise blood vessel, it is corrected at each step.