Abstract: A method for measuring the position of a virtual characteristic point (PRV) associated with the face of a person wearing corrective lenses, said method comprising: acquiring at least two images of the wearer's face using an image acquisition means; estimating the position of the face in relation to the image acquisition means; and determining, on the images, the co-ordinates (Xpref, Ypref) of reference points associated with the face. Given that the virtual characteristic point is visible on at most one image and that the position of the virtual characteristic point is connected to the co-ordinates of the reference point(s) by a predetermined geometric relationship, the measurement method also comprises calculating at least one of the co-ordinates (XPRV, YPRV, ZPRV) of the virtual characteristic point (PRV) on the basis of the reference point(s), using the geometric relationship.

Abstract: The invention relates to a system that is used to aid in determining vision correction. The inventive system is characterised in that it combines: a camera which can take animated images of the subject's face along a determined visual axis; a display device which represents the images taken by the camera; an accessory which can be worn by the subject in a fixed manner on the head and which bears a plurality of visual reference marks; means which form the visual reference mark(s) and which can cover at least two determined regions in relation to the camera; and image-analysis means which can analyze the position of the visual reference marks in the images taken by the camera and deduce therefrom the position and spatial orientation of the accessory and, consequently, the subject's head when the subject is looking at a visual target, in order to ascertain information relating to the visual behaviour of the subject when the subject moves the direction in which he/she is looking.