ask the labs
by Karlen McLean, ABOC, NCLC and Martine Bruneni

TINTING TIPS

Q Are there any standards about what color tint gives the best protection? Is there a percentage of gradient recommended?

-- Michelle C., technician

A I am not familiar with any standards for gradient tints. However, sunglasses with a transmittance of 12 to 15 percent are considered to be safe and effective. Determining if a gradient provides adequate protection depends on the nature and duration of sun exposure. Sunglass-density lenses with a gradient tint, worn inside an automobile, may make it easier for the wearer to see the instrument panel. By contrast, someone who spends time outdoors probably would not enjoy much sunglass protection from a fashionable gradient tint.

Brown lenses have a higher absorption of shorter visible wavelengths. The extent of "blue light" hazard seems to be a matter of dispute, and according to some scientists, undue concern has been raised on this topic. Brown and gray-brown sunlenses are popular in Germany and Middle Eastern countries. Neutral gray has been the color-of-choice in the U.S., with brown tints being next. With either color, transmission of UV rays can be effectively controlled.

--Sam Odom, director of professional services, HOYA Vision Care North America

POLARIZED COLOR

Q What are the advantages to the different polarized lens colors?

-- Doug Kollar, ABOC, Lapeer County Vision Centers, Lapeer, Mich.

A Personal preference, sport performance, and safety are points for consideration. Gray is a natural tint that offers the truest possible optics with no color alteration. Gray is best in bright sun conditions.

Copper enhances color contrast, depth perception, and detail recognition. It provides the truest color enhancement without lasting color alteration. Copper is a great multi-use tint for bright sun conditions or in low-light, hazy, flat-light conditions.

Yellow enhances color contrast and is best used in foggy, low-light conditions to enhance color in an otherwise gray day.

-- Steve Rosenberg, president and founder, Kaenon Polarized

Comparing Lenses

Q How do lens optics stack up against the optics typically found in glass lenses, high-quality plastic lens casting, or traditional plastic lenses?

--Gregg Ossip, OD, Ossip Optometry & Ophthalmology, Indianapolis, Ind.

A Crown glass is still the best refracting medium. But today's organic materials also provide excellent refracting abilities with cast lenses. They feature improved surface quality, replicating glass mold surfaces. High-quality plastics have advantages in resolution and clarity.

Differential distribution can be used with cast lens light-based curing to direct more energy to the thicker portions of the lens; hence, organic lenses cured by light have larger blur-free regions.

-- Lorell Stewart, vice president, channel development, Optical Dynamics Corporation

If you have a question you'd like to have answered in Ask the Labs, send it to Karlen Cole McLean. Fax: 215-643-1705. E-mail: mcleank@boucher1.com. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at www.eyecarebusiness.com.