Lenses

The following are some commonly used safety materials used for prescription lenses:

Trivex: (Also known as Trilogy, Phoenix):

Trivex lenses are new to the Australian prescription safety eyewear market. Not only have they just been added to the newly proposed ASNZs 1337.6 standard for MEDIUM impact resistance but they have a few added benefits over the traditional polycarbonate safety material. These include:

• More chemical resistance than polycarbonate
• Lower specific gravity (lighter) than polycarbonate
• Higher Abbe Number (better optical quality) than polycarbonate
• 100% UV protection (same as polycarbonate)
• Scratch resistant (same as polycarbonate)

The above qualities of Trivex, will be an exciting era for the safety eyewear industry.

CR39:

This hard resin monomer used for many current standard optical prescriptions is not recommended for prescription safety glasses. CR39 can be specifically ground to meet low impact standards but not medium impact. CR39 is good for chemical resistance but is thicker and heavier than other prescription safety materials.

Polycarbonate Lenses:

Polycarbonate lenses have long been regarded as the lens material of choice for prescription safety eyewear.

Advantages of Polycarbonate lenses:

• Approved for medium impact protection
• 100% UV protection
• Scratch resistance
• Thinner and lighter than CR39

Disadvantages of Polycarbonate Lenses:

Lower chemical resistance compared to CR39 and trivex

Non-tintable

The table below summarizes general properties of the three materials:

	CR39	TRIVEX	POLYCARBONATE
Abbe No:	58	43-46	29
Approved Impact Resistance:	LOW	MEDIUM	MEDIUM
Refractive Index:	1.49	1.53	1.59
Specific Gravity:	1.32	1.11	1.22
Chemical Resistance: Acetone Perfumes Hairspray Household Cleaners Solvents Windex/Ammonia	GOOD GOOD GOOD GOOD GOOD GOOD GOOD	GOOD GOOD GOOD GOOD GOOD GOOD GOOD	POOR POOR POOR POOR POOR POOR POOR
Scratch Resistance:	YES	YES	YES
100% UV Protection	NO	NO	NO