Which term describes the technique used to correct vertical imbalance by adding BU prism to the more minus lens?

Which term describes the technique used to correct vertical imbalance by adding BU prism to the more minus lens?

• A. Slab off
• B. Seg drop
• C. Image jump
• D. Vertical shift

Answer: (A)

Vertical imbalance happens when anisometropia causes different image heights between the eyes, especially for near tasks. The corrective technique is slab-off, which involves adding a prism slab to the more minus lens to shift its near image vertically so it lines up with the other eye. The prism is chosen to move the near image enough to reduce the disparity, improving binocular fusion and comfort. Other terms describe different ideas: seg drop relates to where the bifocal segment sits rather than altering image height with prism; image jump is a perceptual effect at the segment boundary; vertical shift is a general description of changing image height without specifying the balancing method.

Vertical imbalance happens when anisometropia causes different image heights between the eyes, especially for near tasks. The corrective technique is slab-off, which involves adding a prism slab to the more minus lens to shift its near image vertically so it lines up with the other eye. The prism is chosen to move the near image enough to reduce the disparity, improving binocular fusion and comfort. Other terms describe different ideas: seg drop relates to where the bifocal segment sits rather than altering image height with prism; image jump is a perceptual effect at the segment boundary; vertical shift is a general description of changing image height without specifying the balancing method.