POLYCARBONATE LENSES
Polycarbonate lenses or Polycarb are the standard for which other lenses are held to when it comes to impact resistance. They are used in safety glasses, sports goggles and most children's eye wear. The material also has some other unique built in properties that other lenses don't, making it a great alternative for everyday eyewear (especially rimless and semi-rimless designs). Polycarbonate lenses offer 100% ultra-violet protection, they are light weight, and are considered a type of high index lens or a thin lens (so your glasses don't look thick). Opticals can also cut the lenses into unique shapes or drill holes through them for speciality eyewear, as they are far less likely to crack.
The downside to polycarbonate lenses is that they have a low abbe value. In optical language this means that they have a large dispersion factor which can lead to reduced visual clarity for higher prescriptions or people with a lot of astigmatism. Basically all materials separate light into its principle colours when light passes through it. This is why diamonds sparkle and why we see a rainbow in the sky after a rain storm. The less the separation or dispersion the better it is when it comes to optical clarity. So lens products with a higher abbe value or lower dispersion rate are better visually than those with lower abbe values or higher dispersion rates. Please note though that most people never notice these properties. In fact most people who wear glasses have probably worn polycarbonate lenses at some point in their lives with no problems at all. However, this large dispersion or light separation is often the reason why some people have problems with this particular lens product.
Polycarbonate lenses are not new, as they've been available for nearly 40 years with very little competition until recently. A new product which was introduced to the market in the last 6-7 years to try and improve on Polycarbs weakness (optical clarity) was trivex. Trivex offers the same impact resistance that polycarbonate does, but has improved optical qualities, making it an alternative to those who have traditionally had problems with polycarbonate.
Although these products are both very resistant to breakage, they are both very soft materials and are susceptible to scratching. We always recommend that polycarbonate or trivex lenses be protected with an additional anti-reflective coating to help prevent this from occurring.
