Q. Cleaning glasses in an industrial plant
We have a safety account that uses the pre-moistened cleaning cloths that contain isopropyl alcohol. These look like little wet naps offered in restaurants. Since they have a safety environment with lots of dust, we're wondering if this is a wise way to clean the lenses. We recommended that the employees rinse the glasses under warm water to remove debris before using the cloths. What is your recommendation?

A.
Anytime there is significant dust or debris on the lenses, it is always wise to rinse the lenses with soapy water. For routine use when there is no grit or debris on the lens, simply wiping with the pre-moistened cloth is sufficient. We produce millions of these pre-moistened cloths and every package includes printed instructions that state "Remove folded cloth from packet and lightly brush away dust and grit from lens surface. Unfold lens cloth advice, the pre-moistened cloths will work well.

-John Sexton, sales manager, after market products, nanoFilm, Ltd.

Q. A Renaissance for Glass? 
We rarely use glass lenses, but our lab is now promoting glass as a premium product, talking about glass as if it were something brand new. Why the rising interest in glass?

A.
Glass is gaining strength as a premium product for three main reasons: 1) Frames are smaller, minimizing weight issues; 2) newest glass lenses are thinner and lighter; and 3) glass has moved from a mainstream to a premium "niche" lens product. No other ophthalmic lens is tested as rigorously for impact resistance since all glass lenses must pass a "drop ball" test. Glass lenses generally have a high abbe value with low dispersion and polish beautifully. All Rx and sunglass users between +2.00 and -2.00 would be hard-put to find lenses that deliver better durability, visual acuity, quality, comfort, and beauty than today's glass lenses.

-John Miller, vice president sales, X-Cel Optical Company

Q. Edge cracks in Poly
I am particularly hard pressed to answer a rather common complaint. It regards poly lenses that have small cracks or fissures radiating in from the edges of the lenses. Do you have any opinions on this?

A.
These small cracks or fissures radiating in from the edge can be from unwanted stress due to over tightening in a metal frame (oversized lens). Chemicals can also attack the unprotected edges and possibly migrate into the substrate beneath the coating. My experience is that often it is a combination of both.

-Norm Vallee, Gentex Optics

Q. polycarbonate popsicles?

A.
Unlike sugar or water, polycarbonate does not melt. The melting point is called "glass transitions temperature." It is load dependent and at 66psi(pounds per square inch), that temperature is 273 degrees.

-Polycarbonate Lens Council EB

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