Comparison of aberrations in different types of progressive power lenses.

Recently, computer numerically controlled machines have permitted the manufacture of progressive power lenses (PPLs) with different designs. However, the possible differences in optical performance among lens designs are not yet well established. In this work, the spatially resolved aberrations, at 20 relevant locations, of three PPLs with different designs were measured with a Hartmann-Shack wavefront sensor. The wavefront aberration (WA), its root mean square error (RMS) and the point-spread function were obtained. Spatially resolved plots are shown for all aberrations, astigmatism alone, and for higher order aberrations. The average RMS of all zones is also compared, and the standard deviation is used as a parameter to evaluate the level of hard-soft design. We find differences in the spatial distribution of the aberrations but not in the global RMS, indicating that current PPLs are rather similar to a waterbed, with the aberrations being the water: they can be moved but they cannot be eliminated.