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Spectacles Parts & Glasses Glossary Part #1

LENSES in Glasses, Eyeglasses, Reading Glasses, Spectacles

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This list could also include sunglasses (which themselves go by many names – as written before) are all frames holding lenses – held in front of the eye… for vision correction, physical eye protection or for protection from the sun’s UV.  (Any word in bold italics will have an explanation below headed in bold – except those examples!)

The lenses are made from glass, plastic or polycarbonate and can be coated in various ways.  What is called plastic is often actually CR-39 a trademark registered to it’s developer and is a DADC (diallyl diglycol carbonate) polymer that was introduced in 1941.  “39” just refers to the batch in which it was developed!  The “plastic” materials weigh less and are stronger than glass.  Glass has better clarity and generally can have better filtering qualities. But the highly developed plastics can have better light refraction properties which makes the vision correction more effective in thinner lenses.  Polycarbonate and Trivex lenses are the lightest and most shatter-resistant, making them suitable for eye protection where the optical properties (when you do’t want higher dispersion) is not so important.  They say you can hit polycarbonate with a hammer and it won’t shatter!

Lenses are either corrective/prescription lenses or clear lenses which hold the UV or other protection/filter.

Lens Coating/Treatments include scratch-resistant coatings which can be applied to most plastic lenses giving them similar scratch resistance to glass; hydrophobic coatings designed to ease cleaning ; anti-reflective coatings  to reduce glare, improve night vision and to make the wearer’s eyes more visible; UV protection to ct out the maimm damaging UV rays OR a “multi” coating to combine any or all the above

Clear Lenses are when glasses are not designed for vision correction but for protection, detailed or specialist viewing or sometimes for aesthetic reasons. Safety glasses are simply eye protection against physical damage or against light or radiation damage. Sunglasses are everyday examples of this allowing us better vision in bright lightand protection from ultraviolet.

More to follow in Spectacles Parts & Glasses Glossary Part #2

Including types of lens prescription – COMING SOON…

4 Comments

  1. […] weaknesses (partly in a literal sense) of glass vs. plastic see the earlier glossary/description of glasses/sunglasses lenses in an earlier […]

  2. […] glass lenses but they can scratch more, though some of the newer materials (see the first part of Spectacles Parts & Glasses Glossary) like CR-39 can have built in protection.

  3. […] series of Spectacles Parts & Glasses Glossary we

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