ASK THE LABS
By Joseph L Bruneni

How many is enough?

Q I recently saw an AR coating that claimed to have 11 layers. Are they counting the layers on both sides of the lens as a marketing ploy or is this a better coating? If the coating is better, what are the new layers they have added and how does this improve the AR? Are 11 layers better than the traditional five layers?

A There is a new 11-layer AR stack design called Endura, which incorporates 11 layers on each side of a lens. The new design includes a new, harder, metal oxide material that is then surrounded by a thin buffer layer on each side to add flexibility. This new technology represents one of the first successful attempts to add hardness to the AR stack itself without increasing brittleness. The result is increased abrasion resistance without increased stress. The technology is applied to lenses that already have scratch-resistance coating on both sides. The better the hard coating underneath, the more scratch resistance the AR will have. Typically, this type of coating doubles the Bayer scratch resistance results of the scratch coating itself.

Fortunately, there are also a number of other new super durable AR processes which are helping to dramatically grow the coating market. Essilor�s Crizal, Sola�s UTMC, and Zeiss�s new Foundation Coating all incorporate new hard-coating technologies with new AR stack designs in order to increase scratch-resistance and overall durability. These technological breakthroughs in coatings are producing better AR products, remarkably improved over those available just a few years ago. Retailers and professionals hesitant about promoting and recommending AR coatings should take another look at today�s AR.

�Larry Clark, president, Satis Vacuum of America, Inc.

[Editor�s note: for a list of labs using this new AR technology, call 877-409-9401]

Avoiding Red Noses

Q I have a patient that has an allergy to latex. Is there any amount of latex in nose pads?

�Nancy, Department of Veteran�s Affairs

A We have heard of this problem before. The nose pads that our company manufactures are latex free for that very reason.

However, we continue to receive calls about patients who are sensitive to standard nose pad materials. Nose pads are made of a variety of materials (we make some of titanium and crystal, too), and it should be easy to fit all patients allergy needs.

 �Bob Woyton, product manager, Hilco

Missing Flat Tops

Q I�ve noticed that the number of poly PALs available in Transitions is increasing, but I can�t find any flat tops in poly Transitions. Do you know of anyone producing this lens, or are there plans in the near future to produce them?

�Peter Bratton, Premier Optical, Haddonfield, N.J.

A We had never taken note that there were no Transitions flat top multifocals. If you consider the technology used in Transitions photochromic lenses, the reason is understandable. The Transitions technology applies photochromic treatment (Transitions calls the process VTO, an acronym for variable tint optics) to lenses produced by many of the world�s leading manufacturers. The difficulty with flat tops comes from the raised line found across the top of plastic flat top multifocals. The raised surface evidently interferes with the photochromic application process. Transitions� Alfred Chan tells Ask the Labs that, �Transitions today does not have a segmented polycarbonate VTO lens. We have an active on-going program to develop a technology for this product type, but no plans to commercialize in the near future.�