Comparison of three techniques in measuring progressive addition lenses.

PURPOSE

To measure progressive addition lenses (PALs) by three techniques and to compare the differences across techniques.

METHODS

Five contemporary PALs (Varilux Comfort Enhanced, Varilux Physio Enhanced, Hoya Lifestyle, Shamir Autograph, and Zeiss individual) with plano distance power and a +2.00 diopters (D) add were evaluated under the condition of lateral displacement of the lens (no rotation and no tilt) using three methods. A Hartmann-Shack wavefront sensor (HSWFS) on a custom-built optical bench was used to capture and measure wavefront aberrations. A Rotlex Class Plus lens analyzer operating as a moiré interferometer was used to measure spherical and cylindrical powers. A coordinate measuring machine (CMM) was used to measure front and back surfaces of PALs and converted to desired optical properties. The data were analyzed with MATLAB programs. Contour plots of spherical equivalent power, cylindrical power, and higher-order aberrations (HOAs) in all PALs were generated to compare their differences.

RESULTS

The differences in spherical equivalent and cylinder at distance, near, and progressive corridor areas among the HSWFS, Rotlex, and CMM methods were close to zero in all five PALs. The maximum differences are approximately 0.50 D and located below the near power zone and the edge areas of the lens when comparing the HSWFS and CMM with the Rotlex. HOAs measured both by the HSWFS and CMM were highest in the corridor area and the area surrounding the near zone in all PALs. The HOAs measured by the CMM were lower than those from the HSWFS by 0.02 to 0.04 μm.

CONCLUSIONS

The three measurement methods are comparable for measuring spherical and cylindrical power across PALs. The non-optical method, CMM, can be used to evaluate the optical properties of a PAL by measuring front and back surface height measurements, although its estimates of HOAs are lower than those from the HSWFS.