The invention relates to a method for determining at least one optical design parameter for a progressive ophthalmic lens intended for being provided on a frame (10) selected by a wearer, in accordance with the visual behaviour thereof. According to the invention, the method includes the following steps: a) collecting a plurality of behavioural measurements relating to a plurality of positions and/or directions of the eyes of the wearer during a visual task; b) statistically processing said plurality of behavioural measurements such as to determine a wearing area of the surface of a lens mounted on said frame, said wearing area (ZU) being representative of a statistical spatial distribution of said plurality of behavioural measures; and c) determining at least one optical design parameter for a progressive ophthalmic lens in accordance with a position and/or size of the wearing area.