A device and method for determining under wearing conditions at least one component of the orientation of a correcting ophthalmic lens of eyeglasses relative to the head of a future wearer. Provision is made for mounting a position-identification system (20) on the frame (10) and/or on a presentation lens fitted to the frame, which system includes at least one identification element (60, 70, 80) having at least one known geometrical characteristic, for capturing the image of the identification element in two dimensions in a vertical facial plane, for processing the captured image to measure the captured geometrical characteristic of the image of the identification element that depends on the known geometrical characteristic of the identification element, and for calculating at least one component of the orientation of the lens by comparing the captured geometrical characteristic with the known geometrical characteristic. A method of optically designing the correcting lens is disclosed.
