The invention relates to a method and an apparatus for determining a reference head posture of a subject (1), said method comprising the steps of:a) asking the subject to:a1) adopt an initial head posture wherein he/she directs his/her gaze towards a predetermined direction (18)；a2) move his/her head (2) up and down starting from said initial head posture at step a1), while keeping his/her gaze directed towards said predetermined direction； andb) determining said reference head posture as a function of a movement or a position of at least one eyelid of the subject during the motion of his/her head at step a2).Further, the invention also proposes a method for measuring a distinctive height associated with a frame of a pair of spectacles worn by the subject.Finally, the invention relates to a method for mounting and for verifying the mounting of an ophthalmic lens in a frame of a pair of spectacles.
