An eye specialist is warning parents and students about the misuse of laser pens, which can be purchased easily but have harmed the eyesight of a number of children in recent months.

Laser pens are often used as pointers by teachers in classrooms, and have become popular with some schoolchildren in Chengdu, Sichuan province.

Sold in many stationery shops in the city, most are priced between 5 yuan and 200 yuan ($0.8-$31). They can emit a narrow beam of light in either red, blue or green with a single click of a button.

But pointing a laser beam into a person's eyes can damage the delicate organs. A number of students have sought treatment at the Ineye Hospital of Chengdu University of Traditional Chinese Medicine.

Xie Airui, an eye specialist at the hospital, has received two boys since September whose visual acuity fell off sharply after incidents involving laser pens. The first boy's eyes were burned. He couldn't see an object 10 centimeters away. A checkup showed that the macular area of his retina had been damaged, Xie said.

The macular area is the most sensitive part of the eye and critical for vision, she said.

The second boy, a high school student, was 15 when he sought treatment from Xie in September, after a classmate pointed a laser pen at him.

A test found that the macular areas of both his eyes were burned and had obvious scarring. He could only see objects within 50 centimeters, Xie said.

The resulting scars were consistent with those left by clinical lasers, she said, noting that damage to the macular areas can be permanent.

Four years ago, the General Administration of Quality Supervision, Inspection and Quarantine issued a warning that laser pens could harm consumers. But no market supervisors have taken up the matter in a serious way, according to Xu Bin, a lawyer in Chengdu.