1. A method for determining a fitting position of an optical axis of lenses mounted in spectacles of a person to the position of the person's eyes, comprising the steps of: determining an interpupillary distance (PD) of the person by a processor, the interpupillary distance (PD) determines a relative distance between the optical axis, the processor is configured to: acquire data by capturing a set of successive images, using a predefined movement of the person in front of a camera, representative of the person's eyes during the predefined movement from a first configuration of a face of the person to a second configuration of the face of the person; and calculate morphological and dimensional parameters based on the acquired data; determining the fitting position of the optical axis of lenses to the determined interpupillary distance; wherein the processor is configured to calculate the morphological and dimensional parameters by: measuring a set of morphological parameters PD, di, r and mechanical parameter f, where di is an iris diameter, r is a radius of an ocular globe and f is a focal length of the camera; constructing a projection stage of a PD system and generating a correspondence table that samples a continuous reality of the morphological and dimensional parameters, depending on the following inputs for given image sizes: PDpx, dipx, PD, di, f, z where z is a distance from a center of the person's eyes to the camera, and where PDpx and dipx are image measurements of the data PD and di; establishing a plurality of probability densities, smoothed by a kernel method and distributed into the correspondence table that express at least the following functions: PD=f (PDpx, dipx, f, zi) and di=f (PDpx, dipx, f, zi), where zi (i=1. .. n) are distances between the camera and the persons for the successive images acquired during the predefined movement, and n is the number of images; characterizing the image measurements by detecting a face of the person; detecting and recognizing the person's eyes; descripting irises by parameters of a circle or ellipse represented by a projection of each iris onto an image; and determining values PDpx, a distance between two centers of the images of the irises and dipx, and diameters of the images of said each iris; determining statistically the morphological and dimensional parameters PD, di, f and zi (i=1. .. n) by expressing all the zi parameters, with two parameters: a starting distance z 0 and a distance between two image captures dz; and simulating a set of samplings of the predefined movement to provide a probabilistic determination of the parameters f, PD and di in relation to the measurements PDpx and dipx observed in the images to determine statistically the morphological and dimensional parameters; and optimizing the morphological and dimensional parameters non-linearly using a simplex algorithm or an additive texture adjustment algorithm by releasing a constant distance constraint between the zi values and initializing with a previous solution; and defining confidence levels for 3D parameters by searching the set of zi, PD, di, f values to minimize a re-projection error of the irises onto acquired images.