What is another term for the frame pupillary distance measurement?

The frame pupillary distance measurement refers to the distance between the optical centers of the lenses in a pair of eyeglasses, which is crucial for ensuring that the lenses align correctly with the wearer's pupils. This alignment is essential for optimal vision correction and comfort.

The term FPD, which stands for frame pupillary distance, specifically relates to this particular measurement, making it the correct answer. Accurate FPD measurements help opticians create glasses that fit properly and provide the best visual experience.

In contrast, terms like DCB, DBL, and pattern difference do not refer specifically to the frame pupillary distance. DCB usually refers to the distance between the corner of the eye and the center of the lens, DBL pertains to the distance between the bridge of the frame and the lens, and pattern difference relates to the increment of lens size differences rather than the pupillary distance. Hence, these terms are less relevant when discussing the measurement of pupillary distance in frame construction.