What does a concentric design feature in its lens structure?

A concentric design in lens structure indeed features a distance prescription in the center, surrounded by concentric rings that provide varying powers as you move outward. This design allows for different prescription strengths to be delivered progressively across the lens, accommodating the wearer's needs for both distance and near vision. It is particularly beneficial for individuals who require gradual transition zones in their vision correction, such as those with presbyopia.

In contrast, a lens with a single power throughout would not accommodate the varying visual needs that a concentric design offers. A soft edge with a hard center does not describe the function of concentric rings, as it implies a different structural characteristic. Additionally, a color gradient touches upon aesthetic transitions in tints or shades rather than optical power changes, which is not relevant to the functional design of concentric lenses. The concentric design, therefore, stands out for its ergonomic approach to vision correction tailored to the specific requirements of the wearer.