The Structural Flaw of Legacy Progressive Lenses (PALs)
For over six decades, presbyopia correction relied on grinding progressive curves onto fixed lens surfaces. To create an additive reading power (ADD zone), lens manufacturers were forced to accept mathematical optical trade-offs: localized surface steepening causes lateral astigmatism, resulting in peripheral blur, distorted peripheral vision, and the visual phenomenon known as the "swim effect." In commercial retail networks, static progressive lenses continue to generate non-tolerance return rates between 10% and 15%.