Most ic berlin eyewear has a bit of a curvature at the frame front, called faceform angle. When worn on the face, it will form a slight nice wrap around the face.
The typical faceform angle of ic berlin frames are from about 7 to 15 degree.
frame with faceform angle of 7 degree
frame with a faceform angle of 15 degrees
However depending on your prescription and the lenses you buy, the faceform angle may be reduced, ie.become less wrap .
As only 1.6 index and above lenses are suitable for the steel ic berlin frames and also most high index lenses have flat front curvature, the faceform angle will be greatly reduced (become less curve) when fitted into the ic berlin frames.
You may ask if there is anything wrong. Technically , there isn’t . Without the faceform, the ic berlin frame worn on your face is not as asthetically appealing. One way to overcome this problem is to use spherical lenses in your ic berlin frames. Using spherical lenses however may induce more distortion in the lenses. The higher the prescription, the more distortion there is. In addition, the higher the prescription, the thicker the lens .
With the Seiko A-Zone lenses, we are able to make the lenses more curve and thinner at the same time. With the help of double sided aspheric design, it is able to eliminate the distortion caused by high curve designs. If you have a high prescription like myopia , hyperopia and/or astigmatism, especially astigmatism, you will benefit greatly from the A-zone lenses as visual and power distortion is reduced markedly compared to normal spherical or aspherical lenses.
Notice in the picture above, the front curve of the Seiko A-Zone lens (higher prescription) is much more curved than the aspherical lens on the left with lower power.
From the above picture, you can see that the original faceform angle of the ic berlin frame is more or less retained when fitted with the Seiko A-ZOne lens (1.67 index), even with a prescription of -6.50D. The curvature and asthetic appeal would not be possible when fitted with a 1.67 index aspherical lens.
For more information on Seiko A-zone lens : http://www.seiko-opt.co.jp/en/lens/st/prime/