Reading Bifocal Lenses contain two different prescriptions in the same lens. The primary purpose of glasses bifocals is to provide the optimal balance between distance vision and near vision focusing needs. Eyeglasses bifocal lenses are available with the reading segments in a variety of shapes and widths including sunglasses bifocal options. The most popular reading bifocal is the Flat-Top (also known as straight-top or D-segment), 28 millimeters wide.
Trifocal Lenses
Trifocal Glasses Lenses contain three focal points, usually for distance, intermediate and near vision. A tri focal lens has an added segment above the bifocal for viewing objects in the intermediate zone, which is approximately arm's length away. Trifocal lenses are available with the reading segments in a variety of shapes and widths. The most popular is the flat-top (also known as straight-top or D-segment), 28 millimeters wide.