Which GP design functions more like a FT 28 bifocal lens?

Which GP design functions more like a FT 28 bifocal lens?

• A. Simultaneous design
• B. Translating design
• C. Front surface aspheric
• D. Bitoric aspheric

Answer: (B)

GP bifocal designs come in two main approaches: translating and simultaneous. A translating design uses a distinct near segment at the bottom of the lens that physically moves into the line of sight as the wearer looks down to read. The eye and lid interaction cause the lens to translate so the near portion aligns with the pupil, delivering the reading power when needed, much like a traditional bifocal eyeglass. The FT 28 bifocal lens is a classic example of this translating approach—the near segment is designed to translate into position with gaze, providing near vision when the wearer looks down. That is why it functions most like a translating GP design. In contrast, simultaneous designs place multiple powers in front of the pupil at the same time (via concentric zones or an aspheric front surface). There is no moving segment to align with the line of sight, so these do not mimic the FT 28’s translational mechanism. The same idea applies to bitoric aspheric forms, which are typically designed to alter the surface shape for optical objectives within a simultaneous design framework.

GP bifocal designs come in two main approaches: translating and simultaneous. A translating design uses a distinct near segment at the bottom of the lens that physically moves into the line of sight as the wearer looks down to read. The eye and lid interaction cause the lens to translate so the near portion aligns with the pupil, delivering the reading power when needed, much like a traditional bifocal eyeglass.

The FT 28 bifocal lens is a classic example of this translating approach—the near segment is designed to translate into position with gaze, providing near vision when the wearer looks down. That is why it functions most like a translating GP design.

In contrast, simultaneous designs place multiple powers in front of the pupil at the same time (via concentric zones or an aspheric front surface). There is no moving segment to align with the line of sight, so these do not mimic the FT 28’s translational mechanism. The same idea applies to bitoric aspheric forms, which are typically designed to alter the surface shape for optical objectives within a simultaneous design framework.