The FluoroPerm ST Bifocal is a monocentric,
encapsulated-segment, translating gas
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.