FRIDAY, Oct. 28 (HealthDay News) -- Laura Butler was vacationing in Virginia Beach, Va., when, on a whim, the brown-eyed mom decided to buy a pair of blue contact lenses for $29.99 from a novelty shop.

Driving home to West Virginia the next day, she felt a searing pain in her left eye. The ill-fitting contact lens had formed a suction on her cornea, the delicate, transparent membrane that covers the pupil and iris. She literally had to tear the contact off, leading to a severe and extremely painful injury.

"The window of the car was open, and I thought a piece of wood had flown in and stabbed me in the eye it was so bad," Butler said. "I've had two children and I have never experienced pain like this in my entire life."

Contact lenses are medical devices regulated by the U.S. Food and Drug Administration (FDA). It is illegal to sell them without a prescription in the United States, but Halloween is a time when sales of "special effects," "theatrical" and "decorative" contact lenses spike, experts said. Decorative lenses don't correct vision, but can turn eyes blue, green or purple, or give the look of zombie or cat eyes.

Though there's nothing wrong with buying decorative contacts from an optometrist or ophthalmologist who will make sure the lens fits your eye properly, buying cheap contacts from flea markets, street vendors or beauty supply shops is dangerous, experts warn.

Ill-fitting contacts or contacts that aren't cared for properly can lead to injuries and infections that can cause blindness, said Dr. Thomas Steinemann, a professor of ophthalmology at MetroHealth Medical Center at Case Western Reserve University in Cleveland, Ohio.

"We worry this time of year especially. Halloween is coming up, and people do things on a lark or a dare. And who are the biggest risk takers? Kids," Steinemann said.

He treated one 14-year-old who got a "blinding infection" -- Pseudomonas aeruginosa -- after using nonprescription contacts. The infection came on rapidly, and within 24 hours the girl was in the hospital as doctors worked to save her eye.

"We got the infection under control, but she was left with a scar on the cornea that left her blinded in the eye," Steinemann said. To restore her vision she needed a corneal transplant. "That's a horrible price to pay," he said.

Because our hands and faces are teeming with bacteria, using even properly fitted contact lenses carries the risk of infection, Steinemann said. But eye professionals cut down on those risks by educating contact-lens wearers about proper use and care of contacts, such as never sleeping in contacts and using sterile contact lens solution to store them.

Infections associated with contact lenses can be serious. "Someone can lose a significant amount of vision in 24 hours," Steinemann said.

When Butler got home, she said she curled up into a fetal position because she was in so much agony. The next day she went to the emergency room, where she received antibiotics and painkillers.

She saw an ophthalmologist daily for the first week, and then weekly for 8 weeks. She couldn't drive for more than two months, and has medical bills for thousands of dollars.

Butler said she hopes her story will dissuade others from buying contacts without seeing an eye professional first. "I came close to being blinded for the rest of my life," she said.

The FDA offers these tips on safe use of contact lenses:

• Get an eye exam from a licensed eye doctor (ophthalmologist or optometrist), who will examine your eye, make sure the lenses fit properly and write you a prescription even if the lenses are decorative only.
• Follow directions for cleaning, disinfecting and wearing the lenses, and visit your eye doctor for follow-up eye exams.
• Never share contacts or contact lens solution.
• Seek medical attention immediately if you have signs of possible eye infection, such as redness, pain, discharge or decrease in vision.

More information

The U.S. Food and Drug Administration has more on the safe use of contacts.