Over the past few decades, progressive addition lenses (PALs) have emerged as an effective correction strategy for presbyopic patients. PALs offer a cosmetic and optical advantage to traditional mulitifocals, but they have optical drawbacks inherent to their design—namely, unwanted astigmatism mostly in the inferior periphery associated with the gradual steepening of the lens. Advancements in manufacturing technology and unique design approaches have reduced the magnitude of unwanted astigmatism, its negative impact on the visual system, and offered an array of design choices in the marketplace. Researchers have assessed PALs using several different approaches: psychophysical measures, clinical trials, satisfaction surveys, wavefront measurements, and lens power measurements (astigmatism and mean power). Assessments of PAL optical properties reveal significant differences in the overall distribution of power and astigmatism across lens designs—indicating the possibility that some designs are better suited for specific patients depending on their unique visual needs. Although it is unclear whether a description of the optical properties of a lens is sufficient in determining wearer preference, understanding the optics is a potentially useful starting point when prescribing them to patients. The focus of this research is to measure and classify PALs based on their individual design characteristics.
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