training tips
Super–AR Part II
by Karlen McLean, ABOC, NCLC
Part two of our series on processing super-hydrophobic AR offers solutions to processing specific lens types and materials, and offers ECPs tips on how to keep super-hydrophobic AR processing running smoothly.
SPECIAL ATTENTION
Some lens types and materials with super-hydrophobic AR require additional processing advice. Our experts offer some insider viewpoints and tips on poly, Trivex, high-index, CR39, and on high-minus, tinted, and some hard coated lenses.
POLYCARBONATE
Poly lens material presents complex processing challenges with super-hydrophobic AR.
"With polycarbonate—safety bevel or groove mount—swarf strings can stay on the lens, actually melting into the lens and causing failure," says Sean Tice, quality services manager at Satisloh in Milwaukee, Wisc. "Make sure melted swarf is removed carefully by hand."
Also be aware that micro-fractures from drilling can cause solvent to travel into the fissures, and the coating to peel off or crack. "Change drill bits often so they stay sharp," Tice advises. "Some labs soak drill bits in dish soap, which helps push the swarf through for a smoother drilling experience. Generally, Trivex has less of a melting effect than poly and swarf comes off easier."
Today most edger manufacturers and AR coating companies offer guidelines and suggestions on how to help alleviate these issues. Perhaps the most effective tip is to handle with care.
"A lot of poly lenses are done inminus Rx's with very thin centers, making them somewhat susceptible to cracking and crazing during edging," says Joe Ochoa, senior systems engineer with iCoat Company in Santa Fe Springs, Calif. "Some suggestions to better process poly include reducing the chuck pressure, slowing the cutting cycle, and utilizing the largest chuck size possible for the particular job being processed."
POLY AND TRIVEX
Some super-hydrophobic AR processing tips work with poly and Trivex materials. Not all super-hydrophobic AR works with all materials.
| What ECPs Can Do |
|---|
| Keep these dispensing, processing, and ordering tips in mind when working with super-hydrophobic AR: 1 Remember that super-hydrophobic AR work is premium work. When edging, take time and pay extra attention, using lens and processing technology manuals. Rely on troubleshooting support desks. Be sure to fill out all paperwork thoroughly and accurately the first time. 2 Get new edging equipment and keep it running to full potential. If you don't do in-house lens processing, work with a lab that has the latest AR processing technology and techniques that upgrades, troubleshoots, and maintains equipment regularly. 3 Take advantage of and understand the workings of manufacturer and lab AR programs. For example, Optical Prescription Lab recently started a new AR program. Now, all high-index work 1.60 and up will automatically come with a brand-name AR. If practices want to upgrade to a super-hydrophobic AR, that is done at a slightly higher cost. This means the lab charges more for lenses without AR than with AR. 4 Make AR part of the Rx. Go beyond selling packages. When talking with patients, simply state that single vision lenses are X price and PALs are X price, which includes UV, scratch-resistance, and AR, period. Don't discuss AR! Don't go into a long explanation. Make AR everyday business. |
"Compatibility or incompatibility of some hard coats and substrates can cause adhesion issues with poly or Trivex," Ochoa says. "Some coating operations utilize a primer coat prior to the hard coat to help eliminate any adhesion failures. Changing of manufacturers or even lens types may change coating compatibility, too."
In particular, paying attention to order details and filling in paperwork accurately always matters.
"Each polycarbonate and Trivex lens must have a hard coat applied to the back of the lens before AR can be applied," says Gordon "Scotty" Scott, Jr., vice president of Robertson Optical Laboratories, Inc., in Columbia, S.C. "When a customer has already performed the grinding, we may receive the Rx without knowing the name of the lens manufacturer or the type of backside coating already applied."
They provide customers with a checklist on their lens envelope to indicate the name of the manufacturer, type of material, and backside coating, Scott adds. "Customers may fail to complete this checklist, which leaves us guessing at the best coating to use."
HIGH-MINUS
High-minus super-hydrophobic AR work is prone to slipping and twisting when edging.
"These types of AR jobs are particularly tricky," says Stuart Kosh, president of Kosh Ophthalmic in Pompano Beach, Fla. "To help with high-minus edging, check machine parameters and even change the motor speed. Configure and program the machine differently to better sync with AR properties, since each machine can have its own quirks."
HIGH-INDEX
Taking it slow with high-index materials is crucial for good end results, as these lenses are thinner and flex more easily during processing.
"We use a slower edging speed on high-minus and high-plus jobs, and on high-index jobs 1.60 and up," says Marcus Parker, finishing lab manager, Optical Prescription Lab in Pelham, Ala.
"Aspheric poly and high-index jobs, like 1.74, can flex during edging, causing crazing. Most of the jobs that have 1.0 centers can flex and craze. We use less pressure and a slower speed so that the AR doesn't craze while processing thin lenses," Optical Prescription Lab's Parker notes.
| Hard COATS |
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| There are basically two types of hard coats for AR lenses: tintable and non-tintable. "The best hard coat for AR adhesion and performance is a hard, non-tintable hard coat," says Phillip Vasquez, production manager, AR coating with iCoat Company. "Tintable hard coats are typically softer so that they can absorb tint easily. This is good for tintability but not durability. Generally, the harder the hard coat, the harder the AR." |
TINTING
A small percentage of a lab's AR work may include a request for a fashion tint, and labs report that more and more sunlenses are coming in with AR requests. Knowing the exact tint color and density is crucial to good final results.
"ECPs must send tint samples with the order, since different practices and even people can perceive a tint shade in a different way under varying lighting," states Danny Pugh, president of Optical Prescription Lab in Pelham, Ala. "Tint samples can also vary from practice to lab to manufacturer. We require a tint sample to take the guesswork out of it."
Adds Thomas Pfeiffer, national sales manager of iCoat Company: "Tinting, especially poly, can be challenging. A good quality tintable hard coat must be applied to a lens that's clean and free of contaminants. Proper, careful application and good control of curing times are crucial. Also, maintenance of the coating machine, coating solution, and curing bulb are critical factors to a durable, even tint and coating."
CR39 PLASTIC
While less than 10 percent of Optical Prescription Labs' work is filling requests for AR with a tint, the lab still must take precautions to ensure the results are what the customer ordered.
"When a tint and UV with AR are requested, as on a CR39 lens, the processor tinting the lenses before AR has to use extra care with the processing steps, because doing this compromises the equipment," Pugh says. He adds: "The stripper has to be crystal clear or else other jobs that follow can come out with a slight tint residue from the tinted job." EB
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