Google has unveiled a contact lens that monitors glucose levels in tears, a potential reprieve for millions of diabetics who have to jab their fingers to draw their own blood as many as 10 times a day. The prototype, which Google said will take at least five years to reach consumers, is one of several medical devices being designed by companies to make glucose monitoring for diabetic patients more convenient and less invasive than the traditional finger pricks. The lenses use a minuscule glucose sensor and a wireless transmitter to help those among the world's 382 million diabetics who need insulin keep a close watch on their blood sugar and adjust their dose. They were developed during the past 18 months in the Google X lab that also came up with a driver-less car and Google's web-surfing eyeglasses. But research on the contact lenses began several years earlier at the University of Washington, where scientists worked under National Science Foundation funding. "You can take it to a certain level in an academic setting, but at Google we were given the latitude to invest in this project," said one of the lead researchers, Brian Otis. "The beautiful thing is we're leveraging all of the innovation in the semiconductor industry that was aimed at making mobile phones smaller and more powerful." American Diabetes Association board chairman Dwight Holing said he is gratified that creative scientists are searching for solutions for people with diabetes but warned that the device must provide accurate and timely information. "People with diabetes base very important health care decisions on the data we get from our monitors," he said. The device looked like a typical contact lens when Mr Otis held one on his index finger. On closer examination, sandwiched in the lens are two twinkling glitter-specks loaded with tens of thousands of miniaturised transistors. It is ringed with a hair-thin antenna. "It doesn't look like much, but it was a crazy amount of work to get everything so very small," Mr Otis said at Google's Silicon Valley headquarters. It took years of soldering hair-thin wires to miniaturise electronics, essentially building tiny chips from scratch, to make what Mr Otis said is the smallest wireless glucose sensor ever made. Other non-needle glucose monitoring systems are also in the works, including a similar contact lens by Netherlands-based NovioSense, a minuscule, flexible spring that is tucked under an eyelid. Israel-based OrSense has already tested a thumb cuff, and there have been early designs for tattoos and saliva sensors. A wristwatch monitor was approved by the FDA in 2001, but patients said the low level electric currents pulling fluid from their skin was painful. The Google team built the wireless chips in clean rooms, and used advanced engineering to get integrated circuits and a glucose sensor into such a small space. Researchers also had to build in a system to pull energy from incoming radio frequency waves to power the device enough to collect and transmit one glucose reading per second. The embedded electronics in the lens do not obscure vision because they lie outside the eye's pupil and iris. Google is now looking for partners with experience bringing similar products to market. Google officials declined to say how many people worked on the project, or how much the firm has invested in it.