December 10, 2009 
Contact lenses that darken when exposed to ultraviolet light have been developed by researchers in Singapore…
The lenses contain photochromic dyes that react to sunlight and become darker to protect the wearer’s eyes from UV rays.
Scientists at the Institute for Bioengineering and Nanotechnology (IBN) developed the lenses using a polymer “laced with a network of nano-sized tunnels”, reported the Technology Review (November 10). The tunnels are then filled with photochromic dyes.
The dyes, which are also used in sunglasses, contain molecules that change shape in UV light, allowing the UV rays to be absorbed.
“If the polymer is too rigid, the dye is stuck and can’t transform,” explained Edwin Chow, team leader and a senior research scientist at the Institute. “This pore structure and polymer happens to give the best environment for dyes to react quickly.”
Jackie Ying, director at the IBN and lens developer, claims that the new technology works faster than transition sunglasses currently available to consumers.
The new lenses are part of a wider research project being carried out by the IBN to develop new materials for contact lenses which can dispense drugs and diagnose diseases.
(Search for an earlier published article about it in categorie „News – Ophthalmology“)
Taken from: http://www.optometry.co.uk