Progressive Performance Transitions® LensesTransitions GEN S Polycarbonate Progressive Lenses combine the benefits of polycarbonate material, progressive lens design, and photochromic (transition) technology. These lenses are a great option for people who need clear vision at multiple distances (near, intermediate, and far), want lightweight and impact resistant lenses, and prefer the convenience of lenses that adjust to different light conditions. Lens Thickness Comparison How to Measure PD