Bifocal /



As their name suggests, bifocal eyeglass lenses have two lens powers — one for distance and one for near.

The lower half of a bifocal lens contains the near segment for reading and other close-up tasks. The rest of the lens is usually a distance correction, but sometimes has no correction at all in it, if you have good distance vision.

The Franklin bifocal design remained in style for more than a century. Then in the early 1900s, the invention of fused bifocals offered thinner and more attractive lenses.

In a fused bifocal, a small lens segment for near vision is attached (fused) to a full distance lens.



Flattop bifocal lens (also called a D-seg or straight-top).

The most popular fused bifocal today has a D-shaped near segment rotated 90 degrees so that the flat part of the "D" is facing up. For this reason, D-seg bifocals also are called "flattop" (FT) or "straight-top" (ST) bifocals.

Flattop bifocals are further described by the width of the near segment, measured in millimeters (mm). The most popular FT bifocal is the FT-28, a flattop bifocal with a near seg that is 28 mm wide.

Availibility for organic

Index Segment Size (mm) Ø (mm) Finish Semi-Finish
Organic 1.50 28 70 SPH +2.00 up to -2.00
ADD +1.00 up to +3.00
Base 2, 4, 6, 8 
ADD +0.75 up to +3.50
Organic 1.56 28 70 - Base 1.5, 3, 5, 7 
ADD +1.00 up to +3.00