Comparison of different power distributions for designing freeform progressive addition lenses based on a minimization error function model

We compared different power distributions to design freeform progressive addition lenses (PALs) based on a minimization error function model. We employed straight line, trigonometric, eighth-order polynomial, and directly assigned function curvature laws to process the power distributions over an entire surface and assessed their effects on the PAL design. Four power distribution techniques were constructed to connect far vision and near vision areas. Correspondingly, four PALs were designed, simulated, and machined. The results showed that power distribution from the far vision point to the near vision point, according to the straight line curvature law, caused errors of 0.35 and 0.6 D in the distance and addition power, respectively. The error was reduced by the trigonometric curvature law and further reduced under the eighth-order polynomial curvature law. The assigned curvature law had the lowest error among the four lenses. These results indicate that the outcome of the PAL design is sensitive to different power distributions. The proposed method is expected to help advance the design procedure optimization of PALs in optometry.