Speed performance is crucial for photochromic eyewear, particularly for adjusting from high to low levels of light. "When your car suddenly goes into a tunnel, the amount of light is very dim, so you need your lenses to transform back immediately," says Chow. While this can take minutes with sunglasses, he says, "Our response time is 10 to 20 seconds."

The team is getting ready to test the photochromic contact lenses in animals. The researchers have already tested the lens material, without dyes, on rabbits, and have determined that it is biocompatible. Ying says the main concern in animal tests is to see whether the dyes are successfully contained within the lenses, or if they leak out.

In addition, researchers will work to focus the dyes so that they cover only the corneal region of the eye, to block out the most UV light. The lenses now have dyes distributed throughout, and would darken a wearer's entire iris--a potentially unsettling effect.

The institute has created a spin-off, iNano Pte Ltd., to commercialize the technology. It will initially target markets in Japan and Korea. Ying estimates that photochromic contact lenses will be commercially available within a year.

Jan Bergmanson, director of the Texas Eye Research and Technology Center in Houston, says athletes may benefit the most from such contact lenses. "If you are a tennis player, and you perspire a lot, perspiration on sunglasses may be a distraction," he says. "If you had [photochromic] contact lenses, you wouldn't have to deal with this dilemma. So this may have a market as a sporty lens."

In the meantime, Ying is exploring other applications for the photochromic material, for instance as UV-sensitive tinting for windows and windshields, or as a cheaper coating alternative for sunglasses.

"Coating sunglasses with photochromic dyes is a tedious process involving coating and heating the glasses hundreds of times to get a nice, uniform coating," says Ying. "Instead, we can coat glasses once with our material, and it should work just the same."