The lenses could replace traditional sunglasses.
Transition lenses have been available for eyeglasses for four decades, but the technology has never before been implemented on contact lenses.
The lenses of conventional transition sunglasses are coated with millions of molecules of photochromic, or ultraviolet light-responsive, dyes. Normally transparent, the molecules change shape when exposed to UV light, darkening the lens and absorbing UV rays.
The darkening can accomplish two tasks: it can make the wearer’s vision in bright light more comfortable, and it can protect the eyes against the sun’s damaging rays.
Researchers at Singapore’s Institute for Bioengineering and Nanotechnology developed the photochromic lenses as part of a broader effort to develop new materials for contact lenses that can dispense drugs and diagnose diseases.
The transition contact lenses are made with a polymer laced with a network of nano-sized tunnels that can be filled with dyes. Until now, it was almost impossible to uniformly apply dye coatings to the soft surface of a contact lens.
IBN scientists solved the problem by developing a contact lens that embeds dyes uniformly throughout the material. The researchers created the “spongy” nanostructure by mixing specific amounts of water, an oil solution with monomers commonly used in contact lenses, and a surfactant, which encourages water and oil solutions to mix.
The resulting material had tiny pores and tunnels that could be filled with agents such as UV-sensitive dyes.
By embedding the dye in the material from the start, researchers can pack more dye molecules into the lens, giving the contact lens greater sensitivity to light and a faster response.
It’s so fast, in fact, that initial tests proved the contact lenses faster than traditional transition sunglasses on the market.
That’s important for situations when you walk out of a shadowy office building into a light-filled street, or for drivers who drive into a dark tunnel at 60 miles per hour.
The researchers say response time is 10 to 20 seconds — much faster than the minutes it takes traditional transition sunglasses.
The research team is testing the contact lenses on animals to see if the biocompatible dyes stay contained within the material.
Still, the question remains whether the lenses can transition fast enough to be safe for drivers, athletes and the military.
The researchers are also working on focusing the dyes so they only cover the cornea — otherwise, people will have huge dark discs on their eyes during use.
Spinoff company iNano Pte Ltd. will commercialize the technology within a year, first in Japan and Korea.