New manufacturing processes produce improved lens products.
READY FOR READING
Polarized lenses have been used in sunwear for many decades. While their basic function of reducing glare hasn’t changed, the manufacturing process has improved tremendously, resulting in longer-lasting lenses. Here’s a look at the various ways these outdoor staples are produced today.
THE SANDWICH STRATEGY
Polarized sunglasses lenses cut down glare by eliminating light in one direction. Traditionally, the lenses have been manufactured with a sandwich strategy: A polarized film is placed between two pieces of lens material. The film itself is made by putting crystals on a PVC thin film, heating and stretching the film so the crystals align in the same direction, and then placing it into an iodine solution, or dichroic dye.
The sandwiching technique is called “lamination,” and it’s still used more than any other manufacturing method. Still, improvements in lamination technology have created lenses that will not separate like older versions occasionally did. While KBco The Polarized Lens Company sells mostly polycarbonate polarized lenses in North America (which are made with an entirely different process), in other countries, the company casts its 1.50, 1.60, and 1.67 lenses using an advanced sandwiching technique.
AN INSIDE JOB
Some challenges remain, such as “delamination” (having the lamination film placed unevenly or becoming damaged during the production process). One way to avoid delamination is to incorporate the polarizing film inside the lens. This technique is known as “encapsulation.” During the lens casting process, the polarizing film is suspended inside the mold and the lens material is cast around it, trapping the film internally. Younger Optics’ NuPolar‘ lenses are made this way.
A HARD FINISH
Some lens producers place a polarizing material onto the front surface of the lens, then cover it with a hardcoating that protects it from wear and the elements. Lenses made this way risk becoming ineffective due to scratching. Critics also question the effectiveness of the process. This technique is more popular with plano sun lens companies.
THE BONDING PROCESS
Another method is to bond the polarizing film within the lens. Rather than coating the lens, this process bonds the film within the lens at the molecular level. The polarized lens is then protected with a hardcoat. This is the method used by QSpex for its Quasar‘ lens.
A DYE JOB
A newer strategy to manufacture polarized lenses involves adding molecules that can deliver both photochromic and polarization properties into the lens material. In this technique, special photochromic dyes are activated by UV light. The molecules then change their structure and reach the proper alignment inside the lens to achieve polarization. These changes darken the lens and polarize it. Transitions‘ Vantage™ lenses use this process.
However they are produced, polarized lenses make outdoor viewing more comfortable, in part by sharpening contrast and allowing colors to look bolder, which is why they’ve become the sun lens of choice.
THE NEWEST POLARIZED PRODUCTS
These recently introduced polarized lenses give patients yet more options.
• MAKING THE GRADE KBco and Younger Optics have introduced gradient lenses in brown and gray. These lenses offer polarized protection for distance viewing, but have a much lighter-yet still polarized-bottom portion for seeing electronic devices such as cell phone screens, tablets, ATMs, and auto dash panel arrays.
• GETTING COLORFUL Essilor of America, Inc.’s Xperio UV™ polarized lenses are now available in green-gray, gray, and brown-a welcome array of hues.
• ENTERING AUTO-MATIC MODE Transitions Drivewear‘ lenses from Younger Optics darken in the car and are fully polarized. Likewise, Transitions Vantage™ lenses are photochromic. As they darken in the sun, they also become more polarized.
Sharon Leonard is a licensed optician and contact lens practitioner in the Syracuse, NY, area.
WHERE TO FIND IT:
Essilor of America, Inc. 800-542-5668 • essilorusa.com
KBco The Polarized Lens Company 800-722-8776 • kbco.net
QSpex 888-259-9845 • qspex.com
Transitions Optical, Inc. 800-848-1506 • essilortransitions.com
Younger Optics 800-366-5367 • youngeroptics.com