Even though Trivex has been available for a while now, there is still much debate and confusion about how Trivex and polycarbonate stack up against one another. We'll lay out the facts and attempt to put the question to rest.
Born from the space race in the 1960's and introduced to the ophthalmic lens market in the late 1970's, polycarbonate has been around the block a few times and enjoys a sizeable market share, particularly in children's and safety eyewear due to its superior impact resistance. With a higher index of refraction and lower specific gravity, polycarbonate lenses are thinner and lighter than their plastic and glass counterparts. Inherent UV protection and wide product availability also contribute to its popularity.
Polycarbonate, however, is not without its drawbacks. One of the chief complaints about polycarbonate is its optical quality, or lack thereof. With an Abbe value of 29, polycarbonate's chromatic aberration is the highest of any lens material in use today. Furthermore, with the increase in popularity of drill mount frames, some dispensers are hesitant to use polycarbonate because of its lack of tensile strength and likelihood of cracking around drill holes.
Introduced in 2001 by PPG, as the only lens material other than polycarbonate to pass FDA Impact Resistance Test (@ 1mm CT), the High Velocity Impact Test, and meet ANSI Z87.1 '89 standards, Trivex has been slowly increasing in both popularity and availability. While Trivex has a slightly lower refractive index (1.53 compared to 1.58), it's specific gravity, 1.11g/cm3, makes it the lightest of any lens material available today. Like polycarbonate, Trivex also has inherent UV protection. However, unlike polycarbonate, Trivex has an Abbe value of 45, making it optically superior. Further distinguishing itself, Trivex is ideal for drill mounting. The tensile strength of Trivex makes it highly resistant to cracking around drill holes, so much in fact, Younger Optics guarantees its Trivex products (Trilogy) for life, against stress fractures and drill mount cracking.
In summary, Trivex has the impact resistance and inherent UV protection of polycarbonate. With a lower index of refraction, Trivex may be slightly thicker than polycarbonate, but is lighter, and can be surfaced to the same 1mm center thickness. Trivex rises above polycarbonate with both its optical quality and suitability for drill mounting.
However, a couple of key points we discovered in our testing is first of all when you're dealing with average prescriptions, the differences in the material performance is often negligible, also keep in mind that when any type of coating is added, all bets are off in terms of impact resistance.
Finally, when comparing the price of Trivex to polycarbonate, make sure you are comparing apples to apples. If you are looking at a spherical polycarbonate product, compare it to a spherical Trivex product. You'll likely find the difference to be less than you might think.