1. A method for analysis of a retinal image implemented in a medical system with one or more processors, said method comprising: (a) locating an optical disk on said retinal image and establishing a plurality of circumferences; (b) detecting a plurality of vessels within a region defined by said circumferences' radii using a crease-based algorithm; (c) extracting a plurality of vessel segments based on a deformable models algorithm; (d) measuring a plurality of vessel calibers; (e) classifying each vessel as a vein and an artery; and (f) computing an arteriolar-to-venular ratio from said vessel calibers.