A trend for wearing coloured contact lenses inspired by the pop singer Lady Gaga could damage people's eyes, opticians warn.
Teenagers have taken to wearing circle contact lenses, which make the eyes look bigger, after the New Yorker wore them in her video for the song "Bad Romance".
They achieve their effect by covering part of the white area of the eye, the sclera, which ophthalmologists warn could cause allergies, scarring and infection, risking blindness.
Circle lenses come in a variety of colours such as bright pink and red, and can be bought from foreign websites for around £20, without an eye examination or a prescription. Popular with teenage girls and women in their twenties, they imitate the round, oversize eyes of Japanese anime characters.
Dr James Salz, an ophthalmology professor at the University of Southern California, said: "There are bound to be complications from the way they're being dispensed."
Dr Salz, also a spokesman for the American Academy of Ophthalmology, told the Chicago Tribune: "Kids are going online and buying them like they're an earring or a nose ring. They're not being fit[ted], and all eyes aren't the same shape; some have steeper curves of the cornea, and some eyes are larger or smaller."
Dr Melanie Pickett, assistant professor of clinical ophthalmology at Indiana University School of Medicine, warned that the lenses could fit too tightly. That could decrease the amount of oxygen reaching the eye and if untreated, she said, "the blood vessels can grow through the line of sight, causing permanent vision impairment".
Problems ranged from allergic reactions to corneal ulcers or corneal scarring, she added. She said: "If they're not fitted properly, they can induce sight-threatening complications, such as abnormal blood vessel growth in the cornea."
Dr Assumpta Madu, from the Montefiore Medical Center in New York, said: "There literally is potential for somebody to lose their vision within 24 hours from an infection."