The training of head movements of a person is of interest in particular for wearing progressive spectacles.  A progressive lens is here understood to mean a spectacle lens with different refractive powers for distance correction and near correction of defective vision and generally also presbyopia.  In contrast to single-vision lenses, it is possible with a progressive lens to view sharply a distance range which is specified in a distance point and near point via the refractive power of the progressive lens.  However, the visual impression perceived by a spectacle wearer through the progressive lenses of progressive spectacles depends significantly on the head movement behaviour of said wearer.  The visual impression for a spectacle wearer becomes increasingly clear, the better he is able, using head movements, to ensure that the viewing direction in each case penetrates a region of the spectacle lens that is adapted to a desired object distance.  Wearing progressive spectacles therefore generally requires that the spectacle wearer changes his head movement behavior as compared to seeing without glasses or seeing with single-vision lenses or with contact lenses.  This must be adapted to the geometry of the near zone, the distance zone and the progression channels of the progressive lenses.  Adapting the head movement behavior to progressive spectacles is, however, difficult for a spectacle wearer because in progressive lenses, changing the viewing direction without a corresponding head movement causes a blurred visual impression, and the spectacle wearer does not notice that the cause for this visual impression is an inadequate head movement.  This is because the information of the blurred visual impression contains no information for the spectacle wearer regarding the direction of head movements that improve the visual impression.  In particular, the mere information of a blurred visual impression does not contain any information as to how the spectacle wearer must change his head movement so that he sees a clear picture.  The result of this is that the statistic of natural head movements of the spectacle wearer is crucial for whether the adaptation of the head movement behavior to progressive spectacles is a success or a failure. 
U.S. 2012/018251 A1 describes an apparatus for capturing head postures of a subject in order to ascertain herefrom a preferred head posture so that for the correction of centering data, an ascertained deviation of a habitual head posture from an actual head posture can be taken into consideration. 
U.S. Pat.  No.  6,827,443 B2 discloses an apparatus and a method for specifying one or more lens designs which are adapted to the viewing behavior of a subject.  To this end, in particular head movements of the subject are captured.