The introduction of the first bifocal lenses by ZEISS, as long ago as 1952, represented a real revolution at the time. In the past few years, however, the popularity of bifocals has considerably decreased due to the constant improvement in the quality of progressive lenses.
While a large number of segment shapes existed in the past, the type with a curved top is now the most common in most countries and is indicated in the product name by a "C" (curved). Fewer reflections result on the curved surface than on the straight edge of an S segment (S = straight). Today’s Bifocal lenses from ZEISS therefore provide wearers with improved cosmetic benefits and enhanced functionality.
Bifocal lenses are available with two different segment widths: 25 mm and 28 mm. The number after the "CT" in the product name indicates the segment width in millimeters. The segment width of 25 mm is adapted to standard conditions of use, providing a sufficiently large visual field for reading purposes. The diameter 28 mm provides correspondingly wider fields of view.
For the segments of glass bifocals from ZEISS, materials with different refractive indices are selected according to the addition in order to ensure that, even with higher additions, all bifocal lenses are as thin and flat as possible.
Bifocal ZEISS Flattop lenses are available in a range of materials.