C54975: Progressive power lenses: part 6

In the sixth part of our comprehensive series discussing progressive spectacle lens design, Professor Mo Jalie looks at degressive designs

So far, this series has concentrated on progressive lenses offering vision correction from distance to near. This article will consider modern lens designs targeting correction where the visual demands are more centred around intermediate and near work.

Degressive power lenses

When an emmetrope wears a pair of +1.00 D lenses, the effect is to render the wearer 1.00 D myopic, with an artificial far point at 100cm in front of the lens (figure 1). Objects which lie further than 100cm from the lens appear blurred, and images take on the typical characteristics of pincushion distortion.

Figure 1: Range of vision through near vision spectacles

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