For the lateral projection of the nasal bones, the interpupillary line (IPL) is:

• A. Parallel to the IR
• B. At 30 degrees to the IR
• C. Neutral to the IR
• D. Perpendicular to the IR

Answer: (D)

In a lateral nasal bone projection, you’re aiming for a true lateral view where there is no rotation of the head. The interpupillary line serves as a reference to detect and prevent that rotation. Placing the interpupillary line perpendicular to the image receptor helps ensure the head remains in a true lateral position, so the nasal bones are visualized in their profile without distortion or misalignment. If the IPL were not perpendicular, the head would be rotated or tilted, causing improper superimposition of midline structures and inaccurate depiction of the nasal bones.