Difference Lens Material

any material used during the manufacturing process, i.e. all materials that goes into composition of the basic ophthalmic lens

Lens Material

includes quartz or rock made out of pure silica

- its hardness and low mist retaining property made it ideal

for spectacle lens

- disadvantage: double refracting medium

Natural Media

- plastic polymer

- (1940) developed by Pittsburgh Plate

Glass Industries as the 39th formula o f a

thermosetting plastic called Columbia Resin

- also known as allyl diglycol carbonate

CR-39

-originally developed as "visual armor" for the military

-excellent optics, strength characteristics and lightweight qualities

-ultraviolet light protection is inherent in the material

Trivex

- first developed by a company named Gentex

- thermoplastic Theroplastic lens means it is moldable uncher sufficient heat

- (1950s) marketed under the name Lexan and due to its extraordinary resistance to impact was originally manufactured for

safety devices, Up to this day, it is still sometimes used far polyarbonate materials.

- (1978) first single vision lens appeared for industrial usage

Polycarbonate Lens

amorphous solid material that is obtained by cooling without crystallization, an organic mixture that has been found to fuse at high temperature; "super cooled liquid"

raw materials: sand, sodium carbonate, carbon dioxide

Glass

most commonly used clear glass for ophthalmic lenses; used mainly for single vision lenses and the distance carrier for most glass bifocals and trifocals

Crown Glass

uses lead oxides in its chemical make up to increase its index of refraction

- material is relatively soft, displays a brilliant luster and has chromatic aberration

Dense Flint Glass

main ingredient: barium oxide (25-40%)

- used in the bifocal segment in the Nokrome series of fused bifocals.

Barium Crown Glass