In PAL fitting, what does the fitting cross help determine besides monocular PD?

• A. Fitting height/seg height
• B. Frame width
• C. Vertex distance
• D. Optical center

Answer: (A)

The fitting cross is a vertical reference on PAL lenses used during frame fitting to align the lens’ geometry with the wearer’s eyes. It specifically guides where the progressive corridor should sit relative to the pupil, which in turn determines the fitting height. By placing the cross at the appropriate eye level, you establish the correct vertical position of the lens in the frame (the fitting height), and for lenses with a reading zone, the seg height as well. This ensures the distance portion aligns with looking straight ahead and the near portion lines up when looking downward.

Frame width, vertex distance, and the optical center are not derived from this cross in the same way; they relate to horizontal frame fit, how far the lens sits from the eye, and the lens’ central reference points, respectively.