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DONE BY,S ARYA DAS
2nd YR, 3rd SEMBHARTIMAIYA COLLEGE OF OPTOMETRY
INTRODUCTION
CROWN GLASS
Crown glass resist scratching
It is not easily affected by the environmental factors.
It has a refractive index of 1.523.
This material is low in chromatic aberration.
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HI-INDEX PLASTICS
• It is a very impact resistant lens material.
• Trivex is a triperformance lens material.
• It offers a triple ccombination of :-
(i) Superior optics
(ii) Impact resistance
(iii) Ultra light weight
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NXT material
• Lenses that are made of two or more layers of materials are known as laminated lenses.
• Lamination is done in polarizing lenses to cut out reflected glare.
• Lamination can also be done to increase impact resistance
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