184 Image Analysis and Modeling in Ophthalmology
First the center of the OD was estimated by nding a point that has maximum local vari-
ance. The color morphology in CIE L*a*b* space is used in order to have a homogeneous
OD region. The boundary of the OD was located using a geometric active contour with
variational formulation. Sáez et al. [43] presented a method fully adapted to human per-
ception wherein an edge-based level-set algorithm is applied. Its main contribution is the
utilization of color information during the segmentation. Specically, vector gradients in
CIE L*a*b* are applied in the edge-based level-set algorithm and, instead of the Euclidean
norm, CIE 94 color difference formula is applied to those vector gradients.
11.2.4 ...