A continuous set of personalized designs (design space) for progressive addition lenses (PALs) is investigated. The main goals are (1) to study how the subjects’ perception of a personalized design depends on its position in the design space and (2) to compare the performance of personalized PALs to a conventional PAL with a fixed design.
In a double-blind study, 51 subjects compared Rodenstock Impression FreeSign 3, which is a family of PALs with a continuously controllable personalized design, and Rodenstock Progressiv Life Free, which is a conventional PAL with a single fixed design. The positions and sizes of viewing zones and the softness of gradients of mean power and astigmatism of personalized lenses were customized to individual viewing preferences. These designs were represented as points in a design space comprising a continuum of PAL designs. Subjective ratings and experimental measurements were used to study viewing zone widths, blur gradient smoothness, amount of distortion, the feeling of safety during motion, and overall wearing comfort.
(1) Far viewing zone width (experiments and ratings), near viewing zone width (experiments), blur gradient smoothness, and the amount of distortion (ratings) were significantly dependent on the position of the personalized lens design in the design space. This was consistent with the structure of the design space. (2) 82% of the subjects chose personalized lenses as their favorite. Most subjects reported higher wearing comfort and tolerability with personalized lenses than with conventional lenses.
The designs of the tested personalized lenses were perceived by the subjects as intended. This is a prerequisite to the successful customization of PALs to individual wearing preferences. Possible reasons for the preference of the tested personalized lenses are the optimization with respect to individual wearing conditions and the personalization.