Poly and Trivex: Facts and Fiction
Even though Trivex has been available for years and polycarbonate for decades, there is still much debate, confusion and even long-held myths about how Trivex and polycarbonate stack up against one another. We'll lay out the facts, put the lenses to the test, 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.
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, some dispensers are hesitant to use polycarbonate in drill-mount frames because of its lack of tensile strength and likelihood of cracking around drill holes. We suggest putting the material through your own tests and deciding for yourself.
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 on paper. The tensile strength of Trivex makes it highly resistant to cracking around drill holes. In fact, Younger Optics guarantees its Trivex products (Trilogy) for life, against stress fractures and drill mount cracking.
Trivex vs. Polycarbonate: A Quick Side-By-Side Comparison
Thickness: Polycarbonate has a higher index of refraction than Trivex (1.58 vs. 1.53), so polycarbonate lenses are about 10 percent thinner than Trivex lenses, but as you see in the video, the difference may not even be noticeable.
Weight: Trivex has a lower specific gravity than polycarbonate, making Trivex lenses lighter than polycarbonate lenses theoretically. Again, as you see in the video, this does not always play out in reality.
Optical clarity; Trivex lenses have a higher Abbe value and may produce sharper peripheral vision with less chromatic aberration than polycarbonate lenses. Our informal tests show the difference is highly subjective.
Impact resistance: Polycarbonate and Trivex lenses have similar impact resistance, but remember all bets are of any time a coating of any kind is involved.
UV protection: Polycarbonate and Trivex lenses both block 100 percent of the sun's UV rays without the need for special UV-blocking lens coatings.
Availability: Polycarbonate lenses are available in a significantly wider variety of lens designs and treatment options Trivex lenses.
Cost: Polycarbonate lenses are the clear winner over Trivex in terms of cost
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 in theory. But as our video showed, real-world tests may yield different results.
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 are 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. But generally speaking polycarbonate is going to be significantly cheaper and be available in more options.