What does the term 'frame PD' refer to?

The term 'frame PD' specifically refers to the sum of the A box measurement and the DBL (distance between lenses). This measurement is crucial in opticianry and eyewear prescription, as it helps to ensure that the lenses are aligned properly with the wearer's pupils, facilitating optimal visual comfort and performance. The A box measurement indicates the width of the lens at its widest point, while the DBL measures the distance between the two lenses at the bridge of the frame. Adding these two components together gives the overall frame PD, which is essential for correctly fitting glasses.