Contact lenses that react to the sun

11 Nov 2009

Scientists in Singapore have developed contact lenses that darken in response to ultraviolet light.

The lenses contain photochromic dyes that react to sunlight by becoming darker, protecting the eyes from UV rays. The dyes, which are also used in sunglasses, contain particles that change shape under UV light, altering their colour.

To adapt this technology for contact lenses, scientists from the Institute for Bioengineering and Nanotechnology (IBN) in Singapore created a polymer laced with a network of nano-sized tubes.

The nanostructure was created by mixing specific combinations of "water, an oil solution with monomers commonly used in contact lenses, and a novel surfactant &ndash; a compound that encourages mixing between water and oil solutions,” according to the MIT publication, Technology Review.

The tubes were then filled with photochromic dyes.

This is claimed to be more effective than previous methods, which have attempted to apply the dye uniformly to the surface. Jackie Ying, director of the institute says that the new tube approach ensures uniformity but also allows the scientists to pack in more dye molecules. This means the contact lenses will react to light more quickly.

Edwin Chow, team leader and senior research scientist at IBN, says that the lenses have a response time of 10 to 20 seconds, which is faster than any light-sensitive lenses on the market.

The contact lenses will now be tested using animals to see whether the dyes can be contained or leaks out. The team is also going to attempt to focus the dyes so that they only cover the cornea of the eye and not the entire iris.

Ying says that the photochromic contact lenses could be commercially available within a year.