Method, manufacturing method, and design system of progressive addition lens, and progressive addition lens

A design system of a progressive addition lens, the design system comprising:

• a processor configured to adjust a surface shape of a progressive addition lens to bring a difference V between a state A and a state B closer to a difference W between a state C a state D, wherein
• the state A is when an object at a location O is visually recognized, and the location O is in front of a wearer by a finite distance and on a medial plane of the wearer, the state B is when an object at a location P is visually recognized while the progressive addition lens is worn, the location P is on a side in a horizontal direction of the location O at a constant height in a vertical direction with respect to the location O, and the location P is in a plane that is parallel to a frontal plane,
• the state C is when the object at the location O is visually recognized, and
• the state D is when the object at the location P is visually recognized while a reference single focal lens corresponding to the progressive addition lens is worn or while no lens is worn, wherein
• the difference V is between an angular difference VA and an angular difference VB, wherein the angular difference VA is between a direction of a line of sight of a right eye and a direction of a line of sight of a left eye in the state A, and the angular difference VB is between a direction of a line of sight of a right eye and a direction of a line of sight of a left eye in the state B,
• the difference W is between an angular difference WC and an angular difference WD, wherein the angular difference WC is between a direction of a line of sight of a right eye and a direction of a line of sight of a left eye in the state C, and the angular difference WD is between a direction of a line of sight of a right eye and a direction of a line of sight of a left eye in the state D, and
• the surface shape of the progressive addition lens is adjusted to change the angular difference VB in the state B so that the difference V is within a predetermined allowable range of the difference W.

A progressive addition lens comprising:

• a near portion having power used for near vision;
• a distance portion having power for seeing an object farther than near vision;
• an intermediate portion having a progressive action in which power changes progressively between the distance portion and the near portion;
• and
• a prismatic effect adjustment region that brings a distortion degree of an image due to an unnecessary prismatic effect caused by a progressive action closer to a distortion degree of an image while a reference single focal lens corresponding to a progressive addition lens is worn or while no lens is worn,
• wherein the prismatic effect adjustment region satisfies at least one of following two conditions:
• in a plot when a lens horizontal direction is a horizontal axis and a surface prism difference in a vertical direction normalized by addition power is a vertical axis, a difference between a maximum value and a minimum value of a surface prism difference in the vertical direction in a predetermined location α on a predetermined horizontal cross section of the near portion is 0.2 prism diopter/diopter or more;
• and
• in a plot when a lens horizontal direction is a horizontal axis and a surface prism difference in a horizontal direction normalized by addition power is a vertical axis, an absolute value of a surface prism difference in the horizontal direction is 0.25 prism diopter/diopter or more at a position of x=0 in a predetermined location γ on a predetermined horizontal cross section of the near portion, and a position of x=0 in the predetermined location γ is directly below a prism reference point or directly below a midpoint of two alignment reference marks of a progressive addition lens;
• and
• wherein a position of the predetermined horizontal cross section is where addition power is 85% to 100%.