Ask the Labs
By Joseph L. Bruneni

What's in a Name?

Q I am the marketing coordinator for Value Optical, a retail chain in the Caribbean. A customer of ours was inquiring about sodium lenses, but I was unable to provide him with an explanation as I am not too familiar with this type of lens. I have searched online for information but have not found much of anything on this item. Can you provide any information about this kind of lens or identify Web sites that I can source this information?

 -Danny Jones, Value Optical Limited, Trinidad & Tobago, West Indies 

A No one we talked to has heard of a sodium lens. All glass lenses contain sodium, so we are wondering if "sodium" might be a vernacular term in your part of the world for glass lenses. One other possibility is the customer might have been referring to didymium lenses, made from a special type of glass for reducing sodium flare. They are often used by glassblowers or people who must look directly at bright fired objects.

Polarized Lenses and ANSI

Q What are ANSI standards as they relate to polarized lenses? Is there a statement within ANSI that allows laminated polarized lenses to be thinner? And how does the standard relate to in-mold versus direct laminated lenses?

A Your questions are really more FDA related than ANSI oriented. With that in mind, the answer to the first question is that FDA drop ball requirements are performance-based, which means if the lens passes the test, it can be used. There is no provision for surfacing plastic polarized lenses thinner than conventional plastic lenses (other than polarized poly). Regarding in-mold polarized lenses versus laminated polarized lenses, FDA regulations make no differentiation between the two types of lenses in plastic. Glass polarized lenses are laminated. FDA exempts certain types of glass lenses from drop ball testing. Among these are "custom laminated" lenses and "cemented" lenses. There is some question about whether production glass polarized lenses fall under the "custom laminated" category or the "cemented" category

 -Steve Drake, Director technical services, Signet-Armorlite

What's going on with Poly?

Q I would like to know the current usage of polycarbonate single vision lenses and progressive lenses in the U.S. market and outside of the U.S. market if you have that data available.

-Dr. Eric Rubinfeld 

A Currently, the market share of polycarbonate lenses in the United States is slightly more than 30 percent. The largest portions of those lenses are single vision and progressives, although both bifocals and trifocals are available in polycarbonate. The market share for poly outside of the United States is much smaller. Until recent years, almost all polycarbonate sales were in the United States. That is beginning to change, but lens sales figures are difficult to obtain in other countries. Polycarbonate sales have been growing in Europe, and the lenses are beginning to show up in the Far East, Latin America, and Canada. The largest market share internationally would probably be France because of Essilor's dominance in that country (Essilor is a prime producer of polycarbonate lenses).

 -Polycarbonate Lens Council