Method for determining at least one parameter associated with an ophthalmic device

A method for automatically determining at least one parameter associated with an ophthalmic device selected by an individual, said ophthalmic device comprising a frame referred to as a selected frame, the determination of at least one parameter being carried out from an image of the face of the individual wearing a spectacle frame, referred to as a worn frame, said worn frame being the selected frame, said image being acquired by an image acquisition system, the method comprising:

• detecting at least one characteristic point of at least one eye of the individual on the acquired image and estimating, in the reference frame of the image acquisition system, the three-dimensional position of the characteristic point(s) detected;
• detecting the worn frame in the acquired image and estimating the three-dimensional position of the worn frame in the system coordinate of the image acquisition system by aligning a three-dimensional representation of the worn frame with the worn frame in the acquired image;
• expressing the position of each characteristic point with respect to the three-dimensional representation of the selected frame;
• determining the parameter(s) from the relative position of the eyes with respect to the three-dimensional representation of the selected frame;
• wherein the characteristic point of one eye is the center of its pupil which is computed as the center of a circle representing the iris, said circle being positioned and oriented in three dimensions by computing the minimum of a distance function between the projection of the circle on the image and the contour of the pupil on the image;
• wherein the position of the center of the eyeball of an eye is computed:
• in the case where the point of gaze of said eye is known, as equal to the point situated on the line defined by the center of the pupil of said eye and said point of gaze, at a distance equal to the mean radius of an eyeball;
• in the case where the point of gaze of said eye is unknown, as equal to the center of a sphere of radius equal to the mean radius of the eyeball and for which the iris represents a cutting plane.