Measurement method for visual behavior, design method and manufacturing method for progressive power lens

A method for designing a progressive power lens, comprising:

• a step (a) of ascertaining a head rotation amount that is generated by a subject in a sagittal plane of the subject when gazing at each of a plurality of gaze points that are set at predetermined and known distances different from each other in a forward depth direction with respect to the subject;
• a step (b) of determining an eyeball rotation amount that is generated by the subject when gazing at each of the plurality of gaze points, based on an assumption that a line-of-sight angle from the subject's eyes to the plurality of gaze points when the subject is gazing at each of the plurality of gaze points is equal to a sum of the head rotation amount and the eyeball rotation amount, the number of gaze points being at least three;
• a step (c) of judging visual behavior of the subject by using the head rotation amount and the eyeball rotation amount, or using the eyeball rotation amount;
• a step (d) of determining a correction method for correcting a progressive power lens based on a result of judgement made in the step (c);
• and
• a step (e) of correcting a design of the progressive power lens based on the correction method determined in the step (d).

A method for manufacturing a progressive power lens, comprising:

• a step (a) of ascertaining a head rotation amount that is generated by a subject in a sagittal plane of the subject when gazing at each of a plurality of gaze points that are set at predetermined and known distances different from each other in a forward depth direction with respect to the subject;
• a step (b) of determining an eyeball rotation amount that is generated by the subject when gazing at each of the plurality of gaze points, based on an assumption that a line-of-sight angle from the subject's eyes to the plurality of gaze points when the subject is gazing at each of the plurality of gaze points is equal to a sum of the head rotation amount and the eyeball rotation amount, the number of gaze points being at least three;
• a step (c) of judging visual behavior of the subject by using the head rotation amount and the eyeball rotation amount, or using the eyeball rotation amount;
• a step (d) of determining a correction method for correcting a progressive power lens based on a result of judgement made in the step (c);
• a step (e) of correcting a design of the progressive power lens based on the correction method determined in the step (d);
• and
• a step (f) of processing the progressive power lens based on the design corrected in the step (e).