Progressive-power lens
An eye-side refractive surface 11 of a distance portion is concave and at least part of an eye-side refractive surface 3 of a near portion is a convex region 31 where one or both of principal meridians of the surface are convex. This provides a back surface progressive-power lens capable of solving disadvantages in terms of lens thickness, external appearance and the like in a back surface progressive-power lens in which the eye-side refractive surface is formed of a progressive-power surface.
1. A progressive-power lens comprising:
an object-side refractive surface; and
an eye-side refractive surface, the eye-side refractive surface including:
a distance portion having power to view relatively distant objects;
a near portion having power to view relatively near objects, and
an intermediate portion having power to continuously view intermediate objects between the distant and near objects,
wherein the eye-side refractive surface of the distance portion is concave,
wherein at least part of the eye-side refractive surface of the near portion is a convex region,
wherein the progressive-power lens is configured to provide multiple viewing zones at a time in a single lens,
wherein the distance portion is configured to have a prescribed positive power, and
wherein the ratio of the surface area of the convex region within a circle having a radius of 25 mm from the geometrical center of the progressive-power lens to the surface area of the circle is less than or equal to 30%.
2. The progressive-power lens according to claim 1 , wherein the absolute value of maximum surface power of a principal meridian of the convex region is not greater than 2 dioptres.
3. The progressive-power lens according to claim 1 , wherein at least part of the convex region is outside the circle having a radius of 25 mm from the geometrical center of the progressive-power lens.
4. The progressive-power lens according to claim 3 , wherein the absolute value of maximum surface power of a principal meridian of the convex region is not greater than 2 dioptres.