FROM RAW TO REFINED

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How monomers from major manufacturers impact the final optical lenses produced by lens casters, to help eye-care professionals choose from among the many materials available.

As global marketing manager of PPG Specialty Coatings and Materials, Nathan Troxell has a high-level, global view of lens materials and the overall market for them. In the following interview with Ed De Gennaro, VCPN’s director of professional content, Troxell’s perspective sheds some light on this vital element of eyecare: lens materials.

ED DE GENNARO: Is there a mystique around lens materials?

NATHAN TROXELL: Yes, and I believe some of that mystique is due to the inherent intricacy of polymer chemistry. The complex chemistry needed to make clear, light, strong and comfortable plastic lenses truly is an advanced science that has to be developed and refined to provide valuable consumer benefits and to be compatible with casting and downstream lab processing and finishing requirements.

Once the chemistry is defined, manufacturing processes need to be established and controlled to ensure consistent high quality from lot to lot and shipment to shipment. There are many dynamic parts, and it’s critically important that the company supplying the material stands behind its products and processes

DE GENNARO: Do eyecare professionals (ECPs) know the lens material a lens caster is using?

TROXELL: If you mention lens materials to ECPs they often start listing refractive index numbers: 1.5, 1.53, 1.59, 1.67, etc. From one perspective, we’ve done a disservice by allowing this oversimplification to happen. Instead of considering the complete performance and consumer benefits that a lens material will offer, only one variable is considered or referenced: thinness. The irony is that for many patient prescriptions, the difference in lens thinness across various refractive indices is negligible.

Although it’s helpful to have a simple categorization system for lens materials, I believe the industry has simplified lens materials too much. The optimization of lens material properties, including optical performance and clarity, lens weight and comfort, UV protection, impact resistance and durability as well as lens thinness, should be considered by ECPs in order to provide the best recommendation to address the needs and desires for every patient.

While it is important to be aware of the type or brand of lens material-which we believe is the foundation upon which the final lens is built-it is equally as important to be aware of differences in casting processes and lens quality between different casters.

Ultimately, PPG produces the lens material, and lens casters manufacture the lens. Understanding that connection is critical. The final properties of the lens are influenced by many factors, including the lens material. It’s important that ECPs consider all the parameters of the final lens, such as material, design, coatings, treatments and other factors, when they make recommendations so the patient receives the best lens solution for their vision needs.

DE GENNARO: Are there many differences among lens materials from different manufacturers?

TROXELL: Yes, there absolutely are differences in lens materials from manufacturer to manufacturer. There are even different variations or grades of a single lens material available from individual manufacturers, which provide different performance features and benefits. For example, there is a lot of variation in 1.60 lens materials, which are widely used in Europe and Asia. A urethane-based 1.60 lens material will provide one level of performance while an acrylic-based 1.60 lens material will provide a much different level of performance, yet sometimes these lenses are simply grouped together as “1.60 lenses.”

Most ECPs are not aware of the finer details of these different chemistries. This is why it is critically important that they are confident in and trust their lens suppliers to provide consistent, high-quality lenses made from reliable lens materials.

DE GENNARO: What’s the most utilized lens material in the U.S. and worldwide?

TROXELL: Polycarbonate is the most utilized plastic lens material, at just over 50% in the U.S., followed closely by CR-39 and similar allyl diglycol carbonate (ADC)-based materials. Worldwide, CR-39 and other ADC-based materials are the most popular lens materials at approximately 40% of the global market. Different regions have different trends in lens materials. For example, India still uses upwards of 60% glass lenses.

Some of the regional lens material trends are influenced by the local industry infrastructure, including lens availability and pricing, distribution channel development, lens processing and coating equipment availability and compatibility, as well as other factors.

DE GENNARO: How many worldwide lens material suppliers are there?

TROXELL: That’s not an easy question because some of the chemistry and equipment used to produce optical lens materials are also used to produce chemicals and materials for other industries. This means that some companies might produce a low volume of optical lens materials, or even a single lens material product, within a much larger chemical product offering. If you focus on key lens material suppliers to the optical industry, we would estimate the number to be approximately 20 to 25. If you include the complete global scope of plano sun lenses, readers, ski goggles, visors and other related products, the number of materials and suppliers increases significantly.

DE GENNARO: What’s in store for lens materials in the U.S.?

TROXELL: In the U.S., the availability and usage of Trivex lenses continues to expand with new casters coming on board and new lens designs, formats and options being launched every year. Tribrid material, which has been available in Europe for a couple of years, will soon be launched in the U.S. Tribrid material can be viewed as an extension of the Trivex material family at a 1.60 index.

PPG’s approach to lens material development is slightly different than our competitors. Instead of focusing primarily on one lens property, we strive for the best balance of properties across a wide spectrum of features and benefits. When we developed Trivex material, our goal was to optimize as many lens material features and eyeglass wearers benefits as we could in a single lens material. With Tribrid material, we took that same approach and applied it to the high-index category. Tribrid material has a high Abbe value, a low specific gravity, very good impact resistance, provides 100% UV protection, can be efficiently processed by labs and is thin and light.

Ed De Gennaro, MEd, ABOM, is director, professional content for First Vision Media Group.

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