A method for determining at least one optical design parameter for a progressive ophthalmic lens intended to be fitted in a frame of a wearer, depending on the wearer's visual behaviour, includes: a) placing the wearer in a situation in which he carries out a visual task at a first working distance； b) during this task, determining at least two gaze directions of the wearer at this first working distance in a frame of reference of the wearer's head； c) determining a relative position of a surface related to the frame or to an ophthalmic lens intended to be fitted in the frame； d) determining for each gaze direction at the first working distance the intersection between this gaze direction and the surface so as to establish a map of these points of intersection on this surface； and e) deducing the sought-after optical design parameter from this map.
