The proper sunglasses lenses are crucial to comforting your eyes and enhancing your vision in the bright sunlight. When shopping for sunglasses the many terms used to describe lenses can be very confusing. In this article the term “polycarbonate lenses” will be defined.
Polycarbonate refers to one of many types of plastic-like materials that sunglass lenses are made of. Polycarbonate is an excellent material for sunglasses since it is naturally UVA and UVB absorbing, affording protection from harmful sunlight. Compared to glass lenses, which offer less distortion, polycarbonate lenses are thinner, lighter weight, and will not shatter so, they are considered to be safer. Since the distortion experienced with polycarbonate lenses is acceptable under most circumstances they have replaced the use of the glass lenses for sunglasses especially where danger from shattering glass lenses was more likely to occur like in performance eyewear and eyeglasses for children. Polycarbonate is the same material used for bullet resistant glass in cars and was initially used for safety glasses in the workplace. It is such a hard material that a special diamond blade and grinding wheel must be used to cut and polish the lenses.
Some manufacturers of performance eyewear like Survival Optics Sunglasses (SOS), add steps to the manufacturing process to enhance the property of their eyewear. SOS, in their DuraLite process, form their sunglasses lenses by melting the polycarbonate and then force injecting it into stainless steel molds. The end product is an optically correct and distortion free lens that provides outstanding optical performance and enhanced vision in any lighting condition. It also offers full spectrum UV protection along with the added benefit of reducing eye drying caused by the heat of the sun’s infrared radiation. This aspect of the lenses make them great for those who wear contact lenses or have sensitive, dry scratchy eyes.
Polycarbonate lenses are the most commonly used lenses in performance eyewear because they are low cost, shatter-resistant, and naturally UV absorbing. Like most plastics, polycarbonate lenses are easily scratched so it may be wise to buy sunglasses with scratch resistant coatings for those times when you can’t protect them by storing them in their case.