Health Update: Shades that warn of dangerous rays

'SMART' sunglasses that warn wearers when they exceed the recommended exposures to potentially dangerous ultraviolet rays are being developed by a Californian company, Reliant Technologies. The frames of the glasses contain photosensors and a microprocessor which change the colour of the spectacle to orange or make the lens flicker if 'safe' levels are exceeded, a report in New Scientist says.