Opticians say American teenagers are risking their eyesight by wearing a controversial contact lens to make their eyes look bigger. The trend started after Lady Gaga's music video, Bad Romance, hit screens last year. In the video, the singer's eyes have been digitally altered to make them look bigger and bolder. But several companies making contact lenses in Asia claim to have achieved the same wide eyed look. The product, known as 'circle lenses', covers part of the white area in the eyes to make the pupil look larger. The lenses are illegal to sell in the US because they haven't been approved by federal health officials, but they can bought online from foreign websites. Teenage girls have been buying them from countries like South Korea and Japan, where they're sold freely. The lenses come in a variety of colours including bright pink and red and cost around $20 (£13). 'No quality control' Opticians are worried that the lack of quality control will lead to problems like eye infections, damage to vision, and even loss of vision. Dr Assumpta Madu, from the Montefiore Medical Centre in New York, said: "There literally is potential for somebody to lose their vision within 24 hours from an infection." The Circle Lenses are available to correct poor eyesight or just as a decorative accessory. But doctors are emphasising that contact lenses should only be purchased after an optician has approved a prescription. One company which sells the lenses online is called CircleLens2U. It says it believes the product is safe and has been approved by officials in Asia. The company told Newsbeat: "The lens itself doesn't have any quality problem. They are just like any normal soft colour contact lenses you could found on the market." A YouTube video on how to get the Bad Romance look has had more than 11 million hits. Chantal George, 19, from Pennsylvania, has been wearing them for almost two years. "As of now, I have 15 pairs", she said. "It's like wearing a new shade of make-up, or a new outfit. "I feel like I'm popping in terms of my look for the day." Chantal told Newsbeat she's not worried about wearing them and will continue recommending them to friends. "I say these are like any other contact lenses. They need to have care taken of them, they need not to be worn too often or for too long. "And they're just coloured lenses - just not made in the United States." Source: BBC