Progressive lenses with variable reduced peripheral mean sphere

A computing device comprising a storage medium having instructions stored thereon which when executed by a processor in the computing device cause the processor to perform actions including:

• receiving a lens prescription including sphere S, cylinder C, cylinder axis A and addition Add;
• calculating an improved total merit function Φ′ that modulates reduction of peripheral values of the mean sphere according to the prescription sphere S according to
• Φ′=Φ″0+s(H0)Φ′1.
• wherein an amount of reduction of mean sphere in of the lens peripheral regions is dependent on the prescription resulting from modified merit function Φ″0 such that the greater the hyperopia and/or presbyopia defined in the prescription, the smaller the reduction of the peripheral value of mean sphere and such that when the peripheral mean sphere reduction is relaxed, a near region is made wider,
• wherein Φ″0 leaves unwanted astigmatism unconstrained below cutoff height ycutoff which depends on the prescription mean sphere H0,
• wherein s(H0)Φ′1 is intended to restrict the peripheral mean sphere from growing over a determined bound depending on the prescription mean sphere,
• wherein Φ′1 is computed using a region of the lens and depends on the prescription mean sphere, and the region is determined by at least one region defining function,
• wherein s(H0) is a weight depending on the prescription mean sphere that controls the importance of the term Φ′1 in relation to the term Φ″0,
• preparing a lens according to the results of the improved total merit function Φ′, the preparing including incorporating the improved merit function into a lens surface description file and guiding a cutting tool to generate a surface of the lens according to the lens surface description.