Peripheral power variations in progressive addition lenses.

The peripheral powers were studied in two types of progressive addition lenses: the AO Ultravue 28 and the Essilor Varilux 2. The marginal dioptric power was measured with respect to the vertex sphere with a device adapted to a Nikon projection vertexometer. The graphical representation of the results permits the power variations to be evaluated rapidly. The results demonstrate some optical characteristics of each of the lenses. Thus it is possible to establish a ratio between the peripheral astigmatism and the addition. The angular area of astigmatic zones could also be estimated.