Part I. Seg insect for the "executive" multifocal. (Or it really can be done the way you want it)

Design principles of the one-piece Franklin type bifocal are described and illustrated. Correct (and incorrect) methods for verifying decentration are explained. Examples of typical decentration problems are given as well as explicit instructions for telling the lab how to lay out the blank for surfacing. A formula for determining the maximum frame/lens size that will cut out of a given blank is provided.