1. A method of pupil segmentation in a digital image of a vertebrate eye, said image being an intensity image composed of pixels having each a specific intensity value, the method comprising the steps of: deriving a texture image from the intensity image, said texture image being composed of pixels having each a specific contrast value; forming a combined image by point-wise combining the intensity image with the texture image, identifying a set of pixels in the combined image which fulfill a combined low-intensity and low-contrast criterion; and approximating a boundary of said set by a convex curve and taking said convex curve as a boundary of the pupil.