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Polycarbonate lenses

It is 10 times more impact resistant than normal plastic and were among early high index lenses.
PTI | By HT Correspondent
PUBLISHED ON AUG 07, 2003 06:17 PM IST

Polycarbonate material was made by the American aerospace industry for use in helmet visors and these were worn by American astronauts. This material is also used in bulletproof windows and in aeroplane windows. This is about 10 times as impact resistant as normal plastic. Lenses made from this material were the early high index lenses.

Advantages of polycarbonate lenses:

They have a high impact resistance

They are thinner and lighter than ordinary plastic

They have built-in u-v filters.

The disadvantages are:

Their optical quality does not match the new high index lenses

They have more distortion than ordinary plastic or glass

These lenses are advised for kids, sportsmen and those with eye injuries who may need strong shatter proof glass.

High index lenses: These can be made from glass or plastic. They are thinner and lighter than conventional glass or plastic lenses. They can be made for medium or strong prescriptions.

The advantages of high index lenses are:

They are thinner and lighter than conventional plastic or glass

They can fit into neat and fashionable frames

They have a higher scratch resistance than normal plastic and higher impact resistance than glass.

The disadvantages are:

They are expensive

They are not as scratch resistant as glass.

(Source: Webhealthcentre.com)

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