Bifocals ⇔ Varifocals ⇔ Varilux
Bifocals D28 also known as S28 or straight top.
Are eyeglasses whose corrective lenses each contain regions with two distinct optical powers. Bifocals are most commonly prescribed to people with presbyopia who also require a correction for myopia, hypermetropia, and/or astigmatism.
Franklin's original bifocals were designed with the most convex lenses (for close viewing) in the lower half of the frame and the least convex lenses on the upper. Up until the beginning of the 20th century two separate lenses were cut in half and combined together in the rim of the frame. The mounting of two half lenses into a single frame led to a number of early complications and rendered such spectacles quite fragile. A method for fusing the sections of the lenses together was developed by Louis de Wecker at the end of the 19th century and patented by Dr. John L. Borsch, Jr. in 1908.
Today most bifocals are created by molding a reading segment into a primary lens and are available with the reading segments in a variety of shapes and sizes.
The most popular is the 28 mm flat-top bifocal [ Also known as the straight-top or D-segment), 28 mm wide].
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| D28 Straight Top |
TR28 Trifocal |
R24 Round Segment |
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| D35 Segment Bifocal |
Executive Bifocal |
Executive Trifocal |
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Varifocals
A varifocal lens corrects vision at various focal lengths - near, far and intermediate.
Varilux invented varifocals and sometimes these two names can be confused.
However, it is important to remember that not every varifocal is actually a Varilux lens.
As well as inventing varifocal technology in the 50s, Varilux has been responsible for many great strides in its development. Today, the period of adjustment to Varilux varifocals is shorter than with other varifocals.
Varilux lenses give you sharp, effortless vision from short to mid to long distance and back again.
All Varilux lenses now bear a tiny laser etched signature to ensure you have the genuine product.
You also receive a 'Certificate of Origin' in the form of a Guarantee Card, and all Varilux lenses are covered by an adaption guarantee which means your optical supplier will replace the lens with another type of lens in the very unlikely event that you are unhappy with your Varilux lenses.
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