Which bifocal lens design creates the largest amount of image jump?

The round 28 bifocal lens design indeed produces the largest amount of image jump among the options given. Image jump occurs due to the abrupt transition between the two focal areas of the lens—distance and near vision segments.

In the case of bifocal lenses, the shape and size of the near segment can significantly impact the amount of image jump experienced when a wearer looks from distance to near. The round 28 bifocal has a smaller, circular near segment compared to the other designs listed. This smaller area creates a more pronounced jump in image position because the transition is steep, making the disparity between the two segments more noticeable.

Other designs, like the FT (Flat Top) bifocals, feature a wider and more horizontal near segment, which minimizes the jump by providing a more gradual transition. The Executive bifocal has an entire lower section dedicated to near vision, further reducing the sensation of image jump since the distance view is less abruptly contrasted with the near segment.

Thus, the round 28 bifocal lens design leads to the largest image jump due to its smaller, circular near segment, making the jump more perceptible for the wearer.