L&T: Technology

May
2002

A New Universe







As with most industries, space has been the final frontier when it comes to optical. But now a new lens treatment may take sun specs boldly where they have never gone before.

One of many recent innovations in the sunlens arena, the Voyager from frame manufacturer Silhouette has been billed as a “state-of-the-art” technology since its launch last February. Developed by NASA’s Astronaut Corps, with assistance from Silhouette’s Austria-based R&D team and sunlens maker Christian Dalloz, the lens is made from a polycarbonate substrate and treated with a proprietary soft brown/bronze mirrored tint designed to provide reduced light transmission.
“With UV exposure such an important concern today—what with the link to macular degeneration—these lenses are as applicable to the average Joe on the street as an astronaut,” notes Keith Manuel, OD, a Houston-based practitioner and senior optometrist at NASA’s Johnson Space Center. In addition to providing vision care services to astronauts and their families for the past 11 years Dr. Manuel has also worked to develop new eyewear products, including Voyager, to improve astronauts’ vision in space.

For years NASA had been married to the “typical government-issue aviator frames” until Dr. Manuel says he “finally got them to realize their astronauts performed unique visual tasks under unique circumstances.” Silhouette, which has been NASA’s primary frame provider since the mid-1990s, helped him obtain the necessary materials, and the optometrist began “trial and error” experiments with several combinations of frames, lens materials and lens treatments until he found lenses matching specific tasks. Astronauts bring several pairs of eyeglasses with them on each mission; bifocal wearers, for instance, have three different segment settings for launch, orbit and landing sequences.

“In space, you need durability,” Dr. Manuel says. “You can’t have product failure. If the astronaut is on a space walk, he may not be able to get his hands up to adjust the eyewear on his face for hours. He can’t have the eyewear sliding down his nose. If a screw comes out of the frames, it can be life and death because it can float into the breathing apparatus. And, of course, the astronaut can’t be worrying about his vision with all of these distractions.”

Dr. Manuel believes Voyager improves “astronaut acuity” by addressing a key issue in space travel: light transmission. Not surprisingly, astronauts need special eye protection due to the design of the space shuttle and the nature of the tasks they perform in space. They have increased exposure to ultraviolet and infrared light rays, both of which have been proved bothersome, if not harmful, to the eyes.
“The intensity of light from the sun is much greater when you are working 200-plus miles above the earth’s surface,” says Dr. Manuel.

According to Dr. Manuel, Voyager features a bi-layer metallic flash mirror. The first layer is chromium and the second, outer layer is siliciumoxide, the same as the basic material used for glass lenses. Siliciumoxide offers excellent scratch-resistance and Silhouette researchers say they have achieved excellent coating adhesion through the use of a proprietary base hard coat and vacuum deposition application process.

The result is a durable lens offering excellent visual acuity and light transmission of only 7 percent with a lightweight fit (due, in part, to Silhouette’s specially designed frames). And, the manufacturers have combined the same benefits for a “street version” of the product available in prescription form in various Titan Minimal Art sun styles from Silhouette, with a slightly higher—but still significant—light transmission level of 12 percent.

“Astronauts are obviously a very intelligent crowd,” notes Dr. Manuel. “They are very demanding, in a good way, about the equipment they use, including eyewear. As a result, I think we’ve raised the bar in terms of light transmission and durability. I know from my practice there have been a number of notable innovations in the lens arena in recent years. To me, this product is definitely one of them.”

 

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