Optometry - Journal of the American Optometric Association
Clinical researchProgressive addition lenses—measurements and ratings
Section snippets
Measurement method
The lens measurement method was identical to that previously reported.3 All lenses were measured using the Rotlex Class Plus lens analyzer to provide sphere, cylinder, and axis values across the surface of the lens. The lenses were measured by aligning the prism reference line markings appropriately in the instrument. All of the measurements were made using the Rotlex “DST” mode; hence, all measurements were normalized to an assigned power of plano at the location recommended by the
Results
The criteria for measuring and reporting the zone width, zone area, astigmatism measurements, and ratings are identical to those used in the previous study.3 The rationale for selecting the particular criteria are reported in the previous publication and are not repeated here. Likewise, the validity of the measured widths and areas insofar as they are related to the performance of everyday tasks was discussed in the previous publication and is not presented here.
Discussion
The measurements and analyses of the PALs in this study are performed with the goal of providing clinicians with information that will assist them in providing appropriate treatment options for their patients. There are tradeoffs in the design of a PAL5; therefore, no single design can be optimized for all characteristics. The measurements in this study show that the balance of tradeoffs can vary widely for the various PAL designs in the market. Previous analyses of common visual tasks show
Conclusions
The optical characteristics of the different PAL designs are significantly different from one another. The differences are significant in terms of the sizes and widths of the viewing zones, the amount of unwanted astigmatism, and the minimum fitting height. Reasoning and task analyses3 suggest that these differences can be used to select a PAL design that matches the particular visual needs of the patient; clinical trials studies are required to test this hypothesis.
Acknowledgment
This research is supported by the Center for Ophthalmic Optics Research, a research consortium at Ohio State University. All ophthalmic companies are eligible and invited to join the consortium. The authors do not have any personal, financial, ownership, or consulting relationships with any of the companies in this study.
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