What is the minimum blank size calculation requirement for a wearer with a P.D. of 55 mm and an A measurement of 52 mm?

To determine the minimum blank size for a lens prescription, one must consider both the pupillary distance (P.D.) and the A measurement of the frame. The P.D. indicates the distance between the centers of the pupils, while the A measurement refers to the horizontal distance between the two vertical (highest) points of the frame's front.

For a proper fit, the minimum blank size should ideally be large enough to accommodate the P.D. and provide sufficient lens material for adjustments and fitting. A general guideline for calculating the minimum blank size is to add a certain amount to the P.D. to ensure the lenses can be cut correctly and provide optimal vision.

In this scenario, since the P.D. is 55 mm, one would typically consider adding a few millimeters to ensure adequate lens size. The A measurement of 52 mm is the width of the lens space available, but it does not provide enough material for lenses to be constructed properly if the P.D. exceeds this measurement significantly.

Thus, selecting a minimum blank size of 58 mm provides a balanced margin to accommodate both the P.D. and the requirements for fitting and lens production. This ensures that the lenses can be fabricated without compromising the quality of vision or the fit within the chosen