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Lensometer guide for opticians: reading free-form lenses
Where to read distance power, prism and add on a free-form progressive, what the engravings locate, and why a compensated lens won't match the written Rx.
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· Lenses
Abbe value of lens materials: which one to order
CR-39, polycarbonate and 1.67 high-index compared by Abbe value and specific gravity, what each number means for the patient, and when to order each.
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