Halloween revellers are being warned about the dangers of “spooky” contact lenses.
The coloured cosmetic lenses should only be sold by a registered optician or doctor, who is qualified to provide after-care advice, but are illegally often sold online, in shops and on market stalls.
Experts said people could suffer vision loss or infection from the lenses, with an increased risk for those who share them with friends, wear the same pair year after year, or store them in water.
Badrul Hussain, consultant ophthalmic surgeon at Moorfields Eye Hospital NHS Foundation Trust in London, said: “Each year we treat patients, including children under 16, who have developed eye conditions after wearing cosmetic contact lenses.
“There can be an increase in these problems in the period around Halloween.
“Some of the cases we see, like patients sharing lenses with friends, wearing the same pair year after year well past the expiry date, and storing them in tap water, have devastating effects.
“Most of the patients haven’t been shown how to look after their cosmetic lenses or their eyes properly.
“Not knowing the basics of using contact lenses safely can put you at higher risk of developing painful eye injuries, infections, and in the worst cases, risk of permanent sight loss.
“The cornea, the clear window at the front of the eye, is delicate and can be scratched easily by inexperienced contact lens wearers.
“This can expose the eye to organisms that can cause nasty infections, which in extreme cases can result in permanently impaired, or loss of, vision.”
Vicky McDermott, chief executive of the General Optical Council, said: “When worn safely, the risks associated with cosmetic contact lenses are low.
“However, when lenses are sold illegally, wearers are denied important safety checks and advice, putting them at risk of serious damage to their eyes.
“Party-goers can better protect their sight by buying their lenses from a qualified professional.”