A progressive power lens belonging to a series of lenses according to the present invention is provided. If a first lens and a second lens randomly chosen from the series of progressive power lenses have a common spherical refractive power Sph [diopter] in the distance portions thereof, the Sph is greater than or equal to +1, and a base curve BC.sub.1 of the first lens is smaller than a base curve BC.sub.2 of the second lens, the first and second lenses satisfy a condition: ##EQU1##

Methods and apparatus for creating compressed versions of regular objects are disclosed. According to one aspect of the present invention, a method for creating a compressed version of an object that stores a first representation of a set of data on a heap structure of an object-based computing system includes determining when the first representation of the set of data is suitable for compression. If the first representation of the set of data is compressible, it is compressed to form a second representation of the set of data, and a second portion of memory is allocated on the heap structure. The second portion of memory is substantially smaller than a first portion of memory occupied by the object. Finally, the method includes writing the second representation of the set of data into the allocated second portion of memory. In one embodiment, the method includes resetting a pointer that identifies the object to identify the allocated second portion of memory, and removing the object from the heap structure.