Vision Care Product News

MAY 2017

Product information for optical people.

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Page 55 of 83 VCPN 54 May 2017 gories such as these makes it much easi- er to decide what to provide, depending on the needs of the wearer. CHOOSING A MATERIAL The first decision eyecare profes- sionals (ECPs) must make about any lens material they wish to rec- ommend to a patient is the degree of impact resistance the patient requires. Ophthalmic lens mate- rials fall into three fundamen- tal impact categories: standard impact, safety (industrial) impact and ballistic. Once this is decided, other factors such as weight, thin- ness and scratch resistance should be considered. Understand that if an ECP chooses a safety or ballis- tic impact material, the number of material choices becomes very limited. Even so, it's the ECP's responsibility to recommend all of life's challenges. That's why they use additional tests to determine a material's other physical characteristics in addi- tion to its impact resistance. While their lens materials will pass the FDA regulatory impact test, they are also often capable of much more than that. For example, PPG's CR-39 exceeds the FDA impact test by 18 times, and its Trivex material exceeds it by 400 times, while 1.60 exceeds it by 30 times. Instead of detailed specifica- tions on the impact resistance of a lens material, you can place lens materials into three catego- ries: standard impact, industrial safety and ballistic (see chart). Standard impact materials are capable of meeting or exceed- ing the FDA drop-ball test reg- ulation. Industrial safety lenses meet a higher impact standard defined in the ANSI Z87.1 - 2010 standard. Ballistic level lenses meet a U.S. military standard (MIL-PRF-31013) that requires a ¼-inch odd-shaped projectile to be fired at the lens at 640 to 660 feet per second (about 400 mph) from different angles. Placing lens materials into cate- what's best for the wearer. Despite manufacturer efforts encouraging ECPs to use higher index materials regularly, even for lower powered Rxs, ECPs contin- ue to use material indices suited for an Rx's needs. Another trend worth mentioning is the growth of ballistic level lens materials. Their initial use by police, fire and military personnel has widened to the sports market for anyone who wants that level of protection. For example, that level of protection would be comforting to a parent of a young child. It's important to know that coating a lens weakens it. This includes coatings such as anti- scratch, mirror and anti-reflective treatments. Manufacturers take this into account when creating a new lens material because the finished lens (the coated, cut and edged lens) is what must be capa- ble of passing the impact testing. FUTURE The future of impact-resistant lenses is a bit unclear. There is no dialogue in the U.S. about the need for increased impact resistance or a cry from ECPs or industry representatives to ease the FDA regulation. On the other hand, consumers are increasingly interested in safety. For those who want it, ballistic level lens materials are available for everyday Rxs. Some lens materials companies are working on composite lens materials, which are essentially different materials and coatings laminated/bonded together. This lens "sandwich" can make for an exceptionally impact-resistant lens that has multiple features because of all the layers. VisionCareTechnology Ed De Gennaro, MEd, ABOM, is editor emeritus of First Vision Media Group. WHERE TO FIND IT: COLTS Laboratories 727.725.2323 • // Corning Ophthalmic 800.821.2020 • // HOYA Vision Care, North America 877.528.1939 • • // Mitsui Chemicals America, Inc. 914.253.0777 • // PPG Industries, Inc. 800.323.2487 • • • // Wiley X, Inc. 800.776.7842 • • Trivex exceeds the FDA impact test by 400 times. SELECTED COMMONLY USED LENS MATERIALS BY IMPACT CATEGORY Refractive Index PPG CR-39 plastic 1.499 polycarbonate 1.586 PPG Trivex 1.527 PPG Tribrid 1.607 MR-6 1.6 plastic 1.595 MR-8 1.6 plastic 1.592 MR-7 1.67 plastic 1.658 MR-10 1.67 plastic 1.661 Hoya EYRY 1.7 MR-174 1.74 plastic 1.732 crown glass 1.523 Corning Clear 15 glass 1.523 Corning Clear 16 glass 1.601 Corning 1.7 1.700 Standard x x x x x x x x x x x x x x Safety x x Ballistic x x FACTORS IN LENS MATERIAL SELECTION • impact resistance • optically clear (of material and resolution) • weight (specific gravity) • thinness (index of refraction) • Abbe value • durability (scratch resistance) • availability (Rx range, lens design) • ability to process the material • surface and edge • tint and coat • drill, notch and groove • price

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