A warning has been issued over the use of decorative lenses this Halloween as they can cause lens damage, infections, impaired vision or even blindness.

The decorative lenses can be purchased for around £5 throughout the UK and on the internet and have been labelled as a real threat to sight by the American Academy of Ophthalmology (AAO). They are a popular costume accessory for Halloween, making party-goers’ eyes look spooky.

“The difference is your traditional contact lens is supplied through an eye doctor’s office with an exam, fit, training and monitoring for any risk,” said Dr Elizabeth Becker, an optometrist in Oxford. “The decorative ones appear in all sorts of other venues from gas stations to places selling costumes to online.”

“A contact lens that’s not fitting properly can squeeze the cornea and block blood vessels at the edge of the cornea. It can be sight-threatening. Also, you don’t know the source of the contact lenses, if they’re sterile-packed, how old they are…. It’s just like getting a drug from Mexico online instead of your pharmacist. It might be OK to end up with a scar on your leg, but it’s not OK to end up with a scar on the middle of your eye.”

The US Food and Drug Administration (FDA) recommends that people have an eye exam with their optician, who can then prescribe the special Halloween lenses, and make sure they are fitted properly.

They can also teach how to properly look after contact lenses. Lenses should not be shared, and you should avoid using them if they have been stored for a long time. Additionally, they need to be cleaned properly, using lens fluid, and not with tap water or saliva.

If you experience any irritation when wearing decorative lenses, ensure they are removed, and do not wear them until you consult your doctor or optician.