Back-surface progressive power lens

A progressive power lens having a negative dioptric power for distance vision, wherein a progressive surface is formed on the back surface of said progressive power lens;

• wherein the value of a surface power Pfm of said progressive surface in the main meridional plane at a first point on the main meridian in a distance portion of said progressive power lens is less than the value of a surface power Pfs of said progressive surface in a plane perpendicular to said main meridional plane at said first point (Pfm<Pfs);
• wherein the value of a surface power Pnm of said progressive surface in said main meridional plane at a second point on said main meridian in a near portion of said progressive power lens is greater than the value of a surface power Pns of said progressive surface in a plane perpendicular to said main meridional plane at said second point (Pnm>Pns);
• and
• wherein said surface power P is defined by the following condition:
• P=(n−1)/r;
• wherein “n” represents the refractive index of said progressive power lens;
• and
• “r” represents the radius of curvature at one of said first point and said second point on said main meridian in said near portion and said distance portion, respectively.