Dissimilar segs can be used to correct vertical imbalance. Which statement best reflects this?

• A. Vertical imbalance
• B. Myopia
• C. Astigmatism
• D. Presbyopia

Answer: (A)

Vertical imbalance is the situation where the two eyes would need different vertical alignment or prism when looking through near vision, leading to discomfort or diplopia. Dissimilar segments in each eye—placing the near portion at different heights or using different segment powers—adjusts where the near image falls for each eye. This helps equalize the vertical demands between the eyes, reducing the vertical disparity and stabilizing binocular vision at near.

So, using dissimilar segments is a targeted way to manage vertical imbalance, rather than correcting general refractive errors like myopia, astigmatism, or presbyopia themselves.