The FluoroPerm ST Bifocal is a monocentric, encapsulated-segment, translating gas permeable bifocal contact lens.  It uses prism ballast to maintain rotational stability and inferior lens position. 

This design allows the lens to position inferiorly, in primary gaze, so that the add segment does not intrude on the visual axis.  Upon down gaze, the lens translates upward, allowing the segment to position within the visual axis for near vision.  The monocentric design eliminates image jump when translation shifts the focus from distance to near.

The Fluoroperm ST Bifocal is produced in a multiple-step molding and lathing process.  A high-index segment is totally encapsulated within FluoroPerm 60, a material manufactured by Paragon Vision Sciences. It is available in +1.5D, +2.00D and+2.5D add powers and in segment heights from 3.0mm to 5.0mm. The flat-top segment is approximately 6.0mm wide and 3.0mm high. Prism ballast positions the high index segment inferiorly.

With this design, the lens positions in primary gaze so that the near segment does not intrude on the visual axis.