1. A method for detecting outlines for iris comparison, comprising: selecting N candidate outlines of circular form by applying a circle search technique to an image of edges of an iris, optimizing the form and the position of the N candidate outlines, the optimized candidate outlines being determined by using parametric models, a set of parameters being determined for each candidate outline by minimizing a quantity of energy E(C), selecting the best optimized candidate outline wherein the quantity of energy E(C) associated with a candidate outline C is equal to the sum of the edge energy E edge (C) and of the region energy E region (C) of said outline.