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Progressive Addition Lenses 171

2. PD Ruler

Fig. 11.55: Measuring monocular PD with ruler

3. Marking directly on the lens insert

Fig. 11.56: Marking on the lens inserts

After determining the monocular PD, mark their location on the lens insert
in the following ways:
• Place the frame symmetrically and level on the progressive addition
lens layout card.
• At the determined PD, mark a vertical line on each lens insert.
• Place the frame back on the wearers face to check the accuracy of PD.