One in six Americans has worn decorative contact lenses, according to the American Optometric Association. About 25 percent of these people bought them illegally, meaning they did not have a prescription from an eye doctor.

In the past year, at least three lawsuits have been brought against retailers selling illegal cosmetic lenses.

Last year, a targeted operation called “Fright Night” charged 10 California businesses for selling cosmetic lenses without a prescription. Some of the lenses had been contaminated with harmful bacteria.

An online retailer, Candy Color Lenses, has admitted to importing and selling counterfeit lenses across the country.

Lastly, 21 convenience stores in Texas have been charged for selling novelty contacts without prescriptions.

Whether you wore them for one night over Halloween or you want to wear them every day to change your eye color, a poor fitting or unregulated lens can cause sight-threatening complications in a matter of hours.

When a lens is not manufactured properly, toxic chemicals can leach from it and damage the cornea.

Also, pigment that is deposited on the surface of the lens can scratch the cornea. Bacteria on the lens, or even from your hand rubbing your eye, can then infect that open wound.

This leads to bacterial keratitis or a corneal ulcer.

If the cornea scars centrally, this will cause permanent vision loss. Another avenue for infection is the handling and packaging of the lenses.

Being that these lenses are unregulated, they might not be manufactured under sterile conditions or packaged properly.

There are numerous horror stories on the internet of people ending up with severe vision loss from even one night of improper lens wear.

In 2005, the Food and Drug Administration classified all contact lenses as medical devices after reports of eye injuries and infections. The FDA now forbids the sale of such lenses without a valid prescription.

Online retailers are required to verify prescriptions with the prescribing doctor before selling contact lenses. Cosmetic contact lenses can yield beautiful results if worn properly.

At your comprehensive eye exam, your eye doctor can prescribe a properly fitting lens with the correct power, teach you to how safely insert and remove the lens, and educate you on the care of these lenses.

Regardless of how you got your contact lenses, you should immediately see an eye care physician if you experience any redness, pain, light sensitivity, or blurred vision from your lenses.

Infections can progress rapidly, but can be treated and reversed if caught early.

Caroline Bundrick, O.D. is an optometrist practicing at Darling Eye Center, with offices in Bluffton and on Hilton Head Island.