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User Name Thread Name Subject Posted
Al BS: Scratches in Glasses Question??? (66* d) RE: BS: Scratches in Glasses Question??? 10 Jun 06


Regular glasses lenses are made of a material marketed as CR-39. I'm not sure if that means acrylic or not. They are more scratch resistant and less shatter proof than polycarbonate. They are frequently coated for more scratch resistance on both sides of the lens. The optics of polycarbonate are inferior to CR-39 especially away from the optical center, and especially so in strong lenses. Polycarbonate lens blanks come from the manufacturer coated on the front surface for scratch resistance. The back surface of the blank is machined by the optical lab, and therefore has no coating. I could be wrong on the coating thing, but this is my understanding based on 26 years in the optometry business.
Al


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