troubleshooting tips

Polarized Lenses in Rimless Eyewear

by Karlen McLean, ABOC, NCLC

There are basically two types of polarized lenses in the marketplace today, laminated or molded/cast. Laminated polarized lenses adhere the polarized filter between lens material layers. Molded/cast polarized lenses molecularly bonds polarization so it's part of the lens.

Regardless of polarized lens manufacturing, utilizing care in fabricating rimless polarized means the difference between failure and success on a production as well as retail level.

DON'T

DON'T: Use excess pressure when mounting or cut lenses too large. Rimless polarized lenses should fit snugly, but not tightly.

Polycarbonate polarized lenses are particularly sensitive to tension, and precise shape matching is crucial or the horizontal polarization axis and accurate vision through the lenses can be compromised.

Pressure typically exhibits around drill holes, notches, or the edges of semi-rimless lenses.

Increase lens stress by bearing down and tightening screws full bore. Stress marks and lines may not appear immediately.

DON'T: Create gaps. Make sure to edge polarized rimless lenses to specs—especially semi-rimless polarized—or gaps may occur.

Place the groove on the front or get an edge coat to match the color of the polarized tint.

DON'T: Place a semi-rimless bevel so that it's touching the polarized film of a laminated polarized lens. This can cause splitting, as can tightening a semi-rimless suspension too tightly. Place the groove on either side of the polarized film.

DON'T: Use rimless frames without a cushion between the metal and the lens. Lens bushings through drill holes and plastic inserts between the lens and frame connections on semi-rimless frames help avoid lens chipping and breakage.

DON'T: Grind lenses too thin. Thin rimless lenses, especially polarized, have a penchant to chip and break, and the polarized filter can be compromised when lenses are too thin.

DON'T: Overuse springy frames. Any rimless frame that bends easily or has spring hinges may induce unwanted pressure on various points of a polarized lens, causing lenses to show signs of stress.

DO

DO: Use Trivex, a proven-effective rimless material that's resistant to chemicals. Chemical resistance is especially important to help waylay cleaning problems, as when a consumer uses alcohol-based cleaners down the line that may cause cracked lenses. This is especially true at drill holes since the raw lens is exposed at that point, letting harmful chemicals intrude.

DO: Keep equipment in top working order. Poorly maintained equipment can cause myriad problems. A poorly edged polarized rimless lens can underperform, causing remakes and returns.

Above all: keep cutting tools sharp.

DO: Consider an equipment upgrade. Today's automatic edgers offer both automatic and manual settings, so customization can be easily achieved depending on job requirements. Automatic settings can take care of many rimless edging, drilling, and grooving challenges, including safety bevel grooving at a precise angle that helps polarized lenses stay in one piece. Computer-assisted drilling and notching help increase accuracy and reduce tension errors.

DO: Keep electronic data synced for rimless polarized processing and update and monitor developments regularly. Tracers must transmit the right data to your edger, such as accurate polarized wrap lens coordinates, or the lenses won't be edged correctly.

Consider using wrap polarized lenses that don't require software calculations for processing accuracy.

DO: Use the right tools. Stand-in tools can cause breakage during assembly and adjustment. Make sure tools are clean, lubricated, sharp, and appropriately padded. Replace old tools. If you don't have the right tools for the job, make the investment.

DO: Check for polarized lens stress through every processing stage: uncut, after edging, and after mounting. This can help identify problem areas: is the lens coming to the practice from the manufacturer stressed, is the edging process stressing the lens, or are mounting techniques causing stress?

DO: Check the polarization axis alignment prior to dispensing. With all polarized lenses, the polarizer axis must be aligned on the 180° line. Polarization should be at a similar angle and/or amount between a pair of lenses. If this isn't accurate, patients can feel like they're seeing in 3-D. This should be part of the usual lens troubleshooting process if a patient returns with this complaint.

DO: Use the correct drill charts and follow them precisely. Available from the rimless frame manufacturer and also often available online, drill charts are indispensable for getting the right lens fit right off the bat.

DO: Consider new technology. For example, one manufacturer offers a rimless bonding system and another offers frames with no screws. These methods reportedly reduce tension and pressure on the lens and increase ease of fabrication, assembly, adjustment, and wear.

DO: Call manufacturers and wholesale labs for assistance and to obtain polarized-specific media. At least one manufacturer offers a polarized technical hotline. EB