Fig. 1 Commonly used bifocal types. A. Round segment, available in diameters of 15, 22, 25, 28 and 35 mm. B. Flat top, available in diameters of 22, 25, 28, 35, and 45 mm. C. Ultex type, available in diameters of 38 and 40 mm. D. Executive bifocal. E. Round blended, diameter of 22, 25 and 28 mm. F. Curve top, available in diameters of 25 and 28 mm. For each bifocal type the dot designates the location of the optical center of the add. For all types (except D) the location of the optical center is at the center of the segment circle.