Method for determining at least one behavioural parameter of a wearer with a view to designing an ophthalmic lens for a spectacle frame of this wearer, said behavioural parameter being one of the following: - reading distance - ratio of the angular movements of the eye and head, - static or dynamic posture adopted for the habitual activity in question, - ergorama associating with each direction of the gaze the distance between the eye and the point looked at, - variability in the aforementioned behavioural parameters, - position of the spectacle frame of the wearer on his face, and said method including the following steps: a) acquiring a first dataset corresponding to a first representation of the head of the wearer in three dimensions, by virtue of a first image-capturing device, b) determining, from this dataset, the relative position in space of at least three particular predefined morphological points of the face of the wearer, c) acquiring a second dataset corresponding to a second representation of the head of the wearer in a natural posture, comprising at least one image of each of the three particular predefined morphological points of the face of the wearer, by virtue of a second image-capturing device distinct from the first image-capturing device, d) identifying, in said second representation of step c), the image of each of said particular predefined morphological points of the face of the wearer the relative positions in space of which were determined in step b), e) deducing from this identification information relating to the position and/or orientation of the head of the wearer during the determination of said second representation, f) determining, from the information deduced in step e), said behavioural parameter of the wearer. - reading distance - ratio of the angular movements of the eye and head, - static or dynamic posture adopted for the habitual activity in question, - ergorama associating with each direction of the gaze the distance between the eye and the point looked at, - variability in the aforementioned behavioural parameters, - position of the spectacle frame of the wearer on his face, and said method including the following steps: a) acquiring a first dataset corresponding to a first representation of the head of the wearer in three dimensions, by virtue of a first image-capturing device, b) determining, from this dataset, the relative position in space of at least three particular predefined morphological points of the face of the wearer, c) acquiring a second dataset corresponding to a second representation of the head of the wearer in a natural posture, comprising at least one image of each of the three particular predefined morphological points of the face of the wearer, by virtue of a second image-capturing device distinct from the first image-capturing device, d) identifying, in said second representation of step c), the image of each of said particular predefined morphological points of the face of the wearer the relative positions in space of which were determined in step b), e) deducing from this identification information relating to the position and/or orientation of the head of the wearer during the determination of said second representation, f) determining, from the information deduced in step e), said behavioural parameter of the wearer. a) acquiring a first dataset corresponding to a first representation of the head of the wearer in three dimensions, by virtue of a first image-capturing device, b) determining, from this dataset, the relative position in space of at least three particular predefined morphological points of the face of the wearer, c) acquiring a second dataset corresponding to a second representation of the head of the wearer in a natural posture, comprising at least one image of each of the three particular predefined morphological points of the face of the wearer, by virtue of a second image-capturing device distinct from the first image-capturing device, d) identifying, in said second representation of step c), the image of each of said particular predefined morphological points of the face of the wearer the relative positions in space of which were determined in step b), e) deducing from this identification information relating to the position and/or orientation of the head of the wearer during the determination of said second representation, f) determining, from the information deduced in step e), said behavioural parameter of the wearer.