L&T: In the Lens Lab

Apr
2002

Tints Afield





Tints Afield

Athletes find a competitive advantage with tinted
lenses… but are they good for their vision


by John Young

Looking through a transparent-colored medium began with the use of “smoked quartz” lenses in China around the 12th and 13th centuries. One would think, then, that man would by now have discovered all that there is to know about color perception with spectacle lenses. Unfortunately, that is not so.

Color is part of our lives, whether it relates to the shade of a woman’s ensemble, the metallic tone of a Harley-Davidson or the hues found in eyewear. How an observer perceives color with each of these objects depends on the observer—do they suffer from color blindness/confusion? Do they have bad taste?—as well as on other environmental considerations, including the intensity of light on the object being viewed, the angle on which the light is illuminating the object, the angle of the observer and the type of light source (i.e., fluorescence, tungsten, sunlight, etc.). We have all had the occasion to check a color in a specific lighting situation if we know the object will be seen and/or worn more in that environment.

With tinted sports sunwear becoming more popular every year—in an ever-increasing palette—color perception on the athletic field is now an issue. Tints complicate matters because we are looking through a color at other colors with all of the same variants mentioned earlier. There are some things we do understand if only from experience: Colors we view through a colored lens can be enhanced or diminished, depending on the combination of the lens and object color.

A yellow lens, for instance, is sometimes used when playing tennis, which is fine if the tennis ball is green. In this scenario, a yellow lens will improve the wearer/player’s contrast sensitivity, allowing them to see the ball more clearly. A yellow ball on the other hand would significantly reduce contrast to the point that it would be difficult for the wearer/player to see the ball, except as a black silhouette against the sky (something to remember if your opponent is wearing yellow lenses). Of course, that would defeat the purpose of the sport-specific tint.

Competition isn’t the only issue, however. Safety is another concern. At one time, yellow lenses were also sometimes recommended for pilots under the pretense they would enable them to see better in hazy conditions. This was proved false based on anecdotal results from a test conducted at a New England airport. Pilots were asked to view and attempt to see objects on a distant hill on a hot, hazy July day. There was no difference with the glasses on or off except that one pilot stated he was not seeing as much detail with them on. This creates an obvious safety issue. If pilots think their vision will be better due to the perceived brightness caused by the yellow lens, they might become more complacent and less vigilant about the surrounding sky through which they are flying. In addition, light transmittance to the eye is reduced 10 to 15 percent due to the yellow tint. Therefore, a reduction in visual performance in certain tasks—such as reading some of the LCDs on the instrument panel—is possible.

The lesson here is that lens tints can be fun and effective for certain activities. But, they are not appropriate, or even safe, for all activities. We discussed the issue of traffic light recognition with tinted lenses in a previous column (see “In the Lens Lab: Shady Deals,” September, 2000) so I’ll only remind you that care has to be taken in sunglass color selection so that the wearer will still be able to recognize traffic signals. To be safe, I suggest maintaining lens tints for sunglass applications to a minimum of about 20 percent transmittance. Wearers should be able to identify important colors such as traffic lights at this level and higher, while still enjoying benefits of improved contrast for their specific sport or activity.
In the end everyone can enjoy—and benefit from—the variety of colors in sun products with just a modicum of diligence in the area of color. Dispensing them with the appropriate care will hopefully help grow this area of additional opportunity for customer satisfaction and retail profitability.

John Young is an ophthalmic lens expert with more than 25 years experience in the optical industry. He has worked for several lens manufacturers, including American Optical and Essilor, and is the former technical director of the Optical Industry Association. His company, COLTS Laboratories, is a Clearwater, Fla.-based independent lens testing facility designed to provide thorough and accurate quality and performance evaluations of spectacle lens products. His clients include lens manufacturers, wholesale labs, independent research organizations, large retailers and independent dispensers. The lab was the first U.S. ophthalmic testing laboratory accredited by the American Association for Laboratory Accreditation. It is also a Safety Equipment Institute-accredited eye protection/safety test lab. Young can be reached by phone at (727) 725-2323 and by email at
john@colts-laboratories.com.

 

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