Individualized Progressive Lenses Outperform Optimized, Conventional Designs

Customized progressive addition lenses (PALs) that account for vertex distance and wrap and pantoscopic angles outperform lenses with conventional or optimized designs with fixed values — even when those measurements have errors, according to research published in Ophthalmic and Physiological Optics.

Using data from 1900 participants, investigators compared the optical performance of 4 PAL designs, which included a customized design with perfectly measured pupillary distance, vertex distance, wrap and pantoscopic angle measurements, a customized design with measurement errors, an optimized lens design using fixed values for vertex distance, wrap and pantoscopic angle, and a conventional lens design that did not account for these measurements. The team compared the performance of the lenses by simulating the power a lens wearer would perceive with respect to the deviations in measurements. The patient’s true prescription was subtracted from this number, and values closer to 0 indicated less deviation from the prescribed correction (m_f  and m_n for distance and near, respectively).  

The average m_f values were 0.10, 0.06, 0.00, and 0.03 diopters [D] for the conventional, optimized, perfectly measured custom, and customized design with measurement errors, respectively. The m_n values were 0.28, 0.15, 0.08, and 0.10 D, respectively. 

The perfectly measured customized design demonstrated the best far and near vision performance, evidenced by m_f and m_n scores closest to 0. Despite induced measurement errors, the imperfectly measured customized design outperformed the optimized and conventional designs. 

Considering the manufacturing error of the lenses, researchers estimate real-world average metrics for m_f to be 0.12, 0.09, 0.05, and 0.06 D for the conventional, optimized, perfectly measured customized, and imperfectly measured customized PALs, respectively. The m_n values were 0.29, 0.16, 0.10, and 0.11 D, respectively when manufacturing errors were accounted for. 

“We showed that the optimized and individual designs are superior to the conventional form and exhibit superior optical performance,” according to the researchers. “That is because optimized designs consider both the position of wear and minimization of oblique aberrations, whereas conventional designs do not. This result indicates that the individual design has the best optical performance, better than the conventional and optimized designs, even when individual parameters are measured poorly.”

Study limitations include the use of a simulation to determine lens performance. 

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.