Which statement is true about round seg?

• A. Raise by 1 mm
• B. Lower by 1 mm
• C. No change
• D. Raise by 2 mm

Answer: (A)

Round seg refers to the circular reading portion of a bifocal lens and its vertical placement on the lens is chosen to align with the wearer’s line of sight when looking down to read. Because the near segment must come into the visual axis without being blocked by the eyelids or interfering with distance vision, a small upward adjustment is typical. Raising the round seg by about 1 mm places the near portion in the correct position for most users, allowing comfortable use of the reading area while keeping the distance portion usable. Lowering it would shift the near zone downward and often misalign it with the wearer's gaze; no change would fail to account for the eyelid clearance and segment positioning; raising it by 2 mm would likely push the near segment too high and can intrude into the distance portion or cause edge issues.