Higher-index materials reduce thickness but lower the Abbe value, increasing color separation.
Most PALs lack a true prism-neutral zone, so patients experience prism even at straight-ahead gaze.
Thicker lenses in high minus powers refract more steeply and worsen peripheral fringes.
Prismatic effect grows with distance. Patients can pass in-office tests yet struggle in the real world.

Goodrich Optical, 2450 Delhi Commerce Dr. Holt, MI 48842
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