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As Halloween approaches, there's a warning you could put your eye sight at risk by sharing coloured contact lenses.

Experts say it spreads eye disease and increases the risk of corneal ulcers.

They're also concerned the lenses are being sold illegally by people without proper training.

"They shouldn't be supplied by anyone other than an optician or doctor," says Alistair Bridge from the General Optical Council.

"Opticians make sure that contact lenses fit properly and that people get expert advice on how to wear and store them safely."

They also advise taking contacts out at night and never to share or swap lenses.

Experts say TV shows including the Vampire Diaries and Twilight have increased the popularity of coloured lenses in particular.

And there are concerns they're so easily available people will buy them as part of their Halloween outfits next weekend.

Leon Livermore, from the Chartered Trading Standards Institute, says: "Cosmetic contact lenses are often made and distributed on a 'one size fits all' basis and not tailored to the wearer's needs which can increase the risk of eye health issues."

He points out that law states the contact lenses must be dispensed in the presence of an optician or medical practitioner.

"It's essential that cosmetic lenses are fitted by a qualified professional who's able to provide advice on their safe use and ongoing care," he says.

He advises against buying them online or from shops without professional supervision because it's more likely to cause eye damage that could be long lasting.

The General Optical Council has the power to take enforcement action against shops selling the lenses illegally.

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