Will increasing the pantoscopic tilt of spectacles raise or lower the bifocal seg height?

Will increasing the pantoscopic tilt of spectacles raise or lower the bifocal seg height?

• A. Raise the seg height
• B. Lower the seg height
• C. No change
• D. Depends on lens material

Answer: (B)

Pantoscopic tilt changes where you look through the lens by rotating the lens plane about the horizontal axis. When you tilt the frame more toward your face, the eye’s downward gaze through the bifocal shifts to a lower portion of the lens. To keep the near segment aligned with the eye during reading, the segment line on the lens must be lowered. So increasing pantoscopic tilt causes the bifocal seg height to decrease. The lens material doesn’t change this geometric effect; it’s about how tilt alters the vertical alignment between the eye and the near portion of the lens.

Pantoscopic tilt changes where you look through the lens by rotating the lens plane about the horizontal axis. When you tilt the frame more toward your face, the eye’s downward gaze through the bifocal shifts to a lower portion of the lens. To keep the near segment aligned with the eye during reading, the segment line on the lens must be lowered. So increasing pantoscopic tilt causes the bifocal seg height to decrease. The lens material doesn’t change this geometric effect; it’s about how tilt alters the vertical alignment between the eye and the near portion of the lens.