Children could suffer serious eye injuries from playing with laser pointer pens, parents were warned today.

In a letter to the British Medical Journal (BMJ), doctors said youngsters were at risk of burns to their eyes from high-powered laser pointers.

Dr Kimia Ziahosseini and colleagues from the Royal Liverpool University Hospital and Manchester Royal Eye Hospital told how a teenager boy suffered central scotomas (dark spots) after he bought a green laser pointer over the internet and shone the laser beam into his eyes while playing with it.

It cut the sharpness of his vision by half, and tests revealed burns to the surface of the eye and disturbances to the retina, the light sensitive tissue at the back of the eye.

Two months later, his clarity of vision improved but some retinal damage remained.

The doctors warned lasers may only seem to leave an "after-image" but they can actually cause permanent eye damage and "visual loss in later years".

The lasers, which are usually small in size, battery-operated and hand-held, generally emit either red or green light.

According to the Health Protection Agency (HPA), laser pointers have been used by workers when giving presentations for many years with no reports of incidents.

Laser pointers sold in the UK should be classified in accordance with the current British Standard on laser safety, the HPA said.