LONDON, Ont. - They may look cool, but optometrists are cautioning people about the dangers of cosmetic contact lenses that can be purchased online or over the counter in Halloween stores.

“You can change your eye to a white eye or a cat eye but it is definitely something you need to take seriously because this is something you’re putting on the surface of your eye,” says Dr. Christina Schropp, optometrist at Old South Optometry.

Schropp says when people put foreign objects like a contact lenses not fitted by a professional in their eye, it can cause a host of medical problems.

“If they are too large they are irritating under the lids. If they are too loose they are moving far too much on the surface of the eye and they can be scratching the surface of the eye.”

And if your eye gets scratched you’re at a risk of bacterial infections.

Schropp says another common concern she’s seen is when a person leaves the contact in their eyes all night, because that can cause severe damage.

“It can cause inflammation and infection and some people have woken up in the morning and they’ve severely lost their vision.”

If you insist on wearing cosmetic contact lenses this Halloween, Schropp says your safest bet is to make an appointment with your optometrist and get a pair of FDA approved contact lenses properly fit to your eye.

However, if you’ve already bought a pair over the counter or online Schropp says you can still take precautions to make sure what you’ve purchased is safe.

“If you want to be 100 per cent sure have your eye care professional double check those lenses you’ve ordered online. Come in, maybe there is a small fee to do that but then you know they fit properly and they won’t damage my eye and we can teach those patients also how to manage the ins and outs.”