Colored or decorative lenses to make their eyes look darker, larger or a different color has become the latest fad among teenagers, but few are aware of the risks associated with them, a recent survey reveals.

A sample survey of 22 hospitals and clinics nationwide from Oct. 2008 to May 2010 released by the Korean Ophthalmological Society (KOS) on Wednesday showed that 499 patients were treated for misusing either corrective or decorative contact lenses.

Some 25.9 percent of them were found to be suffering from eye strain and deteriorating eyesight due to corneal abrasions. The next most serious complication was corneal infection, followed by allergic or inflammatory reactions, such as redness and itchiness, and symptoms of corneal ulcer, which can cause a permanent loss of vision.

There were 47 cases of corneal ulcer reported. One out of three patients, or 33 percent, were teenagers, up from 23 percent when a similar survey was conducted in 2004.

"Cosmetic contact lenses don't let enough oxygen into the eyes, so prolonged use or misuse can have dangerous consequences," said KOS president Lee Sang-yeul. "Due to a lack of awareness, many contact lens wearers don't take the risks seriously enough."