We’ve come a long way since 1888, when German ophthalmologist Adolf Gaston Eugen Fick created the first practical contact lenses to correct vision. Or as practical as heavy, blown-glass lenses that were 8/10 of an inch in diameter and could only be worn for a few hours at a time can be.

Fast forward to the 21st century, where we have a bevy of corrective lens options from which to choose, including extended wear lenses that can be kept in for periods decidedly longer than Fick’s early glass discs. But with new technology comes an increased requirement for diligence on the part of the wearer, especially when it comes to proper cleaning techniques. And when the user skimps on care, the risk of complications increases; sometimes with devastating — and really gross — outcomes.

Most recently this was evidenced by the story of Lian Kao, a college student in Taiwan who left her lenses in for six months without removing them for cleaning. As reported by the Daily Mail (cue horror film soundtrack): “Medics were horrified when they removed the contact lenses to find that the surface of the girl's eyes had literally been eaten by the amoeba that had been able to breed in the perfect conditions that existed between the contact lens and the eye.” Left unable to see, Kao was diagnosed with Acanthamoeba keratitis, which is first on our list of terrible things that can happen when you don’t clean your contacts properly. (Otherwise known as a contact lens care cautionary tale.)

Acanthamoeba keratitis: 'Bugs can eat your eyeballs'

As the Daily Mail, in a burst of subtlety, described Kao’s case of Acanthamoeba keratitis: “microscopic bug EATS her eyeballs.” (Emphasis theirs.) First recognized in 1973, this rare parasitic infection comes courtesy of Acanthamoeba, a single-cell living organism commonly found in pools, hot tubs, tap water, shower water and contact lens solution. And while the parasite can potentially infect anyone who comes in contact with it, the American Academy of Ophthalmology estimates that over 80 percent of Acanthamoeba keratitis cases appear in contact lens wearers. Apparently, when snuggled in beneath the protection of a contact lens, which they attach to, they can burrow down into the cornea and wreak all kinds of parasitic havoc. With this in mind, remove your contacts before swimming, soaking in a hot tub, and taking a shower. Plus, do not (as in never ever) wash your contact lenses or even your lens case with plain ol’ tap water.

Bacterial keratitis: Infection can destroy your cornea in as little as 24 hours.

Also commonly referred to as a “corneal ulcer” (although not exactly correct, corneal ulcers can happen independently of bacterial keratitis), this is a serious bacterial infection of the cornea that can result in corneal destruction and loss of vision. A distinctive feature of this infection is its rapid progression; corneal destruction may be complete in as little as 24 hours with some of the more virulent bacteria. Contact lens wear is associated with up to 42 percent of bacterial keratitis, with increased risk coming from overnight wear and inadequate lens disinfection; other causes include eye trauma and tainted ocular solutions. Superficial keratitis happens at the top layers of the cornea and when healed generally leaves no scar, but deep keratitis can leave a scar after healing that may or may not affect your vision (if the infection hasn't made mincemeat of your cornea in 24 hours, that is). The bacteria usually responsible for this type of keratitis infection in contact lens wearers is Pseudomonas aeruginosa

Fungal keratitis: Molds or yeast can invade and reproduce deep inside your eye.

Fungal keratitis (or keratomycosis) is an infection of the cornea caused by any of 70 fungi – commonly Fusarium, Candida and Aspergillus – invading the ocular surface and then proliferating. Fuarium keratitis made the headlines back in 2006 when an outbreak of it was linked to Bausch and Lomb’s ReNu with MoistureLoc; a product that was swiftly removed from the market. Once established, fungal organisms can grow from the cornea into the sclera and intraocular structures, causing severe infections that are usually very difficult to treat. They can lead to severe visual loss and even loss of the eye. Fungal infections often start when the eye is injured, providing access for the organisms to penetrate and take over, but they also occur as a result of, and are exacerbated by, improper lens care.

Fortunately for the more than 30 million people in the United States who wear contact lenses, when used with proper care they are relatively benign. “Contact lenses are one of the safest medical devices when worn responsibly,” says Thomas L. Steinemann, MD, a spokesperson for the American Academy of Ophthalmology. Yet according to the CDC, between 40 to 90 percent of contact lens wearers do not properly follow the care instructions for their contact lenses. So, go back and re-read those instructions and follow them closely!

As a quick summary, here are the general contact lens care tips from the FDA medical devices site:

  • Follow recommended wearing schedule.
  • Do not substitute sterile saline solutions for multi-purpose solutions.
  • Rub and rinse your contact lenses as directed by your eye care professional.
  • Do not “top-off” the solutions in your case. Always discard all of the leftover contact lens solution after each use. Never reuse any lens solution.
  • Clean, rinse and air-dry your lens case each time lenses are removed.
  • Do not expose your contact lenses to any water: tap, bottled, distilled, lake or ocean water.

If you have any questions about caring for your contacts, get in touch with your eye care professional, and especially if you experience any symptoms of eye irritation or infection. And basically, just remember to beware the eyeball-eating bugs.