ask the labs

Numbers & Demos

by Karlen McLean, ABOC, NCLC

BY THE NUMBERS

Q Can you tell me what the UV percentages are in poly, 1.60 to 1.74 high index, Trivex, photochromic, polarized, etc.? Also, can you tell me what percentage is considered safe?

— Michelle Wyeth, optician, Tampa, Fla.

A A good percentage of Rxs sold today have transmittance in the UVA region unless UV treatment is specified.

Polycarbonate, high index 1.60 and above, Trivex, polarized (excluding CR39), and photochromic lenses are all 100 percent UV protective. Keep in mind, however, that this is only a small part of the U.S. market, about six to 10 percent.

To my knowledge, there is no specific "safe" number. It depends on usage. As an example, someone primarily outdoors with high exposure to UVB rays may require more UV protection than someone inside or with occasional outdoor use.

— Susie Lesher, vice president-sales, Brondstater Optical America, Inwood, W.V.

Editor's note: UV 400 means protection above the ultraviolet region of the light spectrum. International standards for UV blockage include ANSI Z80.3, ISO 8980-3, EN 1836 and AS/NZS 1067.

D.I.Y. Samples

Q I want to make my own demo lenses to show patients different lens designs (bifocal, PAL, etc.) and materials (poly, high index, Trivex, etc.) so they can hands-on compare lens designs and thinness/lightness. What do you suggest as the best demo lenses and Rx powers? A Pick a current-style unisex frame, using the same frame for all samples, and label the temple with lens power and material. Decenter 5mm OU and edge polish and AR coat the right lens. For thickness, weight, and aspheric vs. spherical comparisons consider: PALs vs. FT28: Make up three pairs, plano distance with 1.00, 1.50, and 2.00 adds; right lens PAL and left lens FT28. Utilize lorgnettes. This way, patients can hold the samples over their current single-vision lenses to get a realistic idea of how both lenses work. Our lab supplies this type of product and service. Contact your preferred lab for assistance with making your own display samples — Paul Zito, president, Encore Optics, LCC, South Windsor, Conn.

If you have a question you'd like to have answered in Ask the Labs, send it to Karlen McLean. E-mail: mcleank@lwwvisioncare.com. Fax: 215-643- 1705. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at www.eyecarebusiness.com.