Patent ID: 7837325

Claim:
A method for designing a progressive addition lens, comprising the steps of: a.) providing a first design for a progressive addition surface which includes a nominal surface power and a nominal cylindrical power that at least in part determine a channel length; b.) calculating a scaled surface power and scaled cylinder power for each of a plurality of base curves based on the nominal surface power and the nominal cylindrical power, so that the channel length is decreased or increased; c.) using the scaled surface and cylinder powers to generate a set of power and cylinder targets; and d.) optimizing the first design using the power and cylinder targets to produce a second optimized design, wherein the scaled surface power or cylinder powers are determined in step b) according to the following equations: P ( x,y )= p ( x′,y′ ) C ( x,y )= c ( x′,y′ ) Wherein P(x,y) is a scaled surface power; p(x′,y′) is a nominal surface power; C(x,y) is a scaled cylinder power; c(x′,y′) is a nominal cylinder power x′=x/x_scale; and y′=(y-shift)/y_scale+shift.