Polycarbonate lenses are thinner and lighter than traditional plastic eyeglass lenses. They also offer 100 percent ultraviolet (UV) protection and are up to 10 times more impact-resistant than regular plastic lenses. This combination of lightweight comfort, UV protection and impact resistance makes polycarbonate lenses an excellent choice for children's glasses, sports eyewear and safety glasses.
Polycarbonate lenses have become the standard for safety glasses, sports goggles and children's eyewear. Because they are less likely to fracture than regular plastic lenses, polycarbonate lenses are also a good choice for rimless eyewear designs where the lenses are attached to the frame components with drill mountings.
How Polycarbonate Lenses Are Made
Most other plastic lenses are made from a cast molding process, where a liquid plastic material is baked for long periods in lens forms, solidifying the liquid plastic to create a lens. However, polycarbonate is a thermoplastic that starts as a solid material in the form of small pellets. In a lens manufacturing process called injection molding, the pellets are heated until they melt. The liquid polycarbonate is then rapidly injected into lens molds, compressed under high pressure and cooled to form a finished lens product in a matter of minutes.
UV and Scratch Protection
Similar to the way sun block prevents the sun's rays from damaging your skin, UV protection in eyeglass lenses shields your eyes from harmful solar radiation. Polycarbonate lenses block 100 percent of the sun's UV rays. This built-in protection is provided by the lens material itself. So there's no need to purchase special UV-blocking lens coatings.
Polycarbonate lenses are actually constructed out of material that is identical to what is called "bulletproof glass." But while polycarbonate is extremely impact-resistant, it's a relatively soft material. This "softness" gives polycarbonate lenses their ability to absorb energy without breaking.
This flexibility also means polycarbonate lenses need a scratch-resistant coating to prevent surface scratches. Today's modern scratch-resistant coatings can make the surface of polycarbonate lenses nearly as hard as glass to protect against scratches.
In a test to determine the strength of polycarbonate lenese, a BB was shot at three different lenses worn by a mannequin. The first lens, made of polycarbonate, didn't break into pieces because it had more "give." The second lens (plastic) and third lens (glass) were completely shattered.
Because polycarbonate lenses hold up better under impact, they are recommended in children's glasses, sports goggles and safety eyewear
Proper Frames for Polycarbonate Lenses
Polycarbonate's impact resistant nature could tempt you to forgo purchasing a proper sports frame to instead wear a regular "dress" eyeglass frame to play basketball, racquetball and so forth.
The danger in not using a sports frame is that, while the polycarbonate lenses provide eye protection, a regular eyeglass frame is not capable of holding up to the impact of a ball or racquet. Therefore, playing sports while wearing polycarbonate lenses in an eyeglass frame that is not rated for sports eyewear is dangerous and defeats the purpose of using polycarbonate lenses for safety.
TSO Doctors of Optometry always recommend polycarbonate for all types of children's frames because kids tend to be rough at play even when they are not taking part in an organized sport.
