Colored or patterned contacts that temporarily change the color of the eyes are increasingly popular among teen-agers and can be ordered online without prescriptions. But it may be exchanging permanent harm for temporary fun.

"Buying contact lenses without a prescription is breaking the law of common sense by risking your eyesight as well as breaking the law, period," says Dr H Dwight Cavanagh, professor of ophthalmology at UT Southwestern Medical Center at Dallas. "Ill-fitting contact lenses could cause an infection that might lead to blindness."

"Contact lenses are medical devices," he says, "not fashion toys."