Glass led the way in optics for decades. Glass is a hard material and very resistant to scratching but is also prone to shattering on impact and is heavier than most modern materials.
One key advantage in glass is its excellent optical clarity, making it a good choice for fashion and lifestyle sunglasses but not so much for the rough and tumble of active or sports sunglasses. Ray-Ban still offers toughened forms of glass which undergo strenuous testing for this reason, and Julbo offers protection category 4 glass lenses for high-altitude use thanks to their clarity.
CR-39 is a plastic polymer and for several decades has been one of the most common lens materials.
The material was made for the military as a durable, lightweight plastic to be used on aircraft. A company based in the US state of Ohio named Columbia Southern Chemical Company initiated a project named “Columbia Resins” and managed to create the desired product on the 39th attempt, in May 1940, creating the abbreviation “CR-39”.
CR-39 is about half the weight of glass. In itself this confers many advantages, and during the 1970s it enjoyed a popularity boom as it could be used in larger frames which were the fashion of the time. Another advantage of CR-39 is the ease with which the lens material can be tinted, making this lens a great choice for fashionable lifestyle frames.
The greater thickness of CR39 compared to polycarbonate makes it unsuitable for high-prescription eyewear, but it is a great cost-effective choice for lower prescriptions.
Like CR-39, polycarbonate is a plastic polymer but confers many advantages its predecessor does not. Polycarbonate became a popular choice during the 1980s for several reasons.
Lenses made using this material are 25% thinner than plastic while also being extremely strong under impact and scratch resistant after coating. Another key advantage is polycarbonate’s ability to block UVA/UVB light while CR-39 cannot without a lens treatment.
Polycarbonate’s qualities make it an excellent choice for active and sports eyewear, and it has become the most popular lens material in the industry thanks to its excellent versatility and inherent UV protection.
A relative newcomer onto the scene, Trivex was another lens material developed for the military, as visual armour. The material was then later adapted for use in the optical industry.
Trivex takes some of the key advantages of both CR-39 and polycarbonate and merges them. It is easy to tint, can offer UV blocking and is practically unbreakable. To stand them apart, Trivex lenses also offer crisper optics and sharper vision than their polycarbonate counterparts.
The light transmission of untreated Trivex (91.4%) is one of the highest of all lens materials, this makes it an excellent choice for photochromic lenses which can go from a dark tint to a nearly clear tint.
Trivex is gradually displacing polycarbonate as a lens material of choice in sports and safety eyewear. Bolle, Julbo, Rudy Project and Serengeti all offer Trivex options in their range, though a limiting factor at this time is the higher price tag for the material.
We would love to be a part of your next sporting adventure. No matter if you are carving turns on the slopes or taking on an uphill challenge, we want to share your journey on our socials. Just tag our eyewear in your post and use the hashtag #RxSport
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