The Walking Dead Halloween
A woman poses in her costume at the Sinchon district of Seoul on Oct. 31, 2015. Getty Images

Wearing crazy-colored contact lenses might complete a costume look, but health experts are warning against the accessories.

Many contact lenses sold online or over the counter are not sold legally and are not approved by U.S. Food and Drug Administration. The FDA needs to approve contact lenses because they are considered medical devices, even decorative sets.

Risks Of Wearing Halloween or Other Decorative Contact Lenses

Wearing unprescribed decorative contact lenses can lead to an infection, blindness, decreased vision, itchy or watery red eyes or a cut or scratch on the top layer of the eyeball. The contact lenses that are not purchased under a prescription might not have the right fit for the user’s eye, which could scratch the cornea, which is needed to focus most of the light that enters the eye.

“[The] fitting of a contact lens by a professional is critical to eye health and safety,” Dr. Roy S. Chuck, chair of the ophthalmology and visual sciences department at the Montefiore Health System and Albert Einstein College of Medicine, told International Business Times. “Everyone's eye is unique and ill-fitting contact lenses can result in devastating consequences like infections and blindness.”

Fashion contact lenses sold at stores aren’t well regulated, meaning it’s not always easy to know what materials are being used, and “impossible to guarantee cleanliness and sterility,” Chuck said.

“We've seen many cases of corneal damage from use of over the counter contact lenses, the worst cases can result in corneal transplants and worse,” Chuck said.

He said last week he saw another “overwhelming infection” case that led to the loss of over 50 percent of the cornea in a young adult.

“The patient is still undergoing intensive therapy and we can only hope for the best,” said Chuck. “Even in best cases, the vision will never be the same.”

Signs Of An Eye Infection

Redness, pain in the eye or eyes that persists after a short period of time and decreased vision could be signs of an infection after wearing sketchy decorative contact lenses. The FDA recommends people with those symptoms to immediately see an optometrist or ophthalmologist, since an untreated eye infection could come serious and could cause blindness.

The FDA has previously warned against buying the accessories from street vendors, beauty supply stores, flea markets, novelty or Halloween stores. However, more education about the issue is needed.

“Public awareness is key,” Chuck said. “We tend to only hear about the positive cosmetic benefits, including from our celebrities, and not the blindness that can result.”

People who really want to wear decorative lenses need to get a prescription for it.

“Regulated cosmetic contact lenses can be prescribed, after proper examination and fitting, by an experienced ophthalmologist or optometrist,” said Chuck.

The prescription should include the brand name, correct lens measurements and expiration date, the FDA says. The agency has a list of cleared or approved contact lenses online.