I'm embarrassed to admit that I have some doubt about this matter, but doesn't the dioptric power of a curve (given the radius of curvature) vary depending on the index of the lens being measured?

For example, say you are given a polycarbonate lens with a sag (at 40mm) of 1.75. The radius of curvature is going to be 114.21mm (or thereabouts). If the lens had an index of 1.53, the dioptric value of that radius of curvature would be 4.64 diopters. However, considering that polycarbonate has an index of 1.586, the lens really has a front curve value of +4.81 Diopters... correct?

Thanks for your confirmation or refutation.