The Sneaky Eye Parasite That's Targeting Contact Lens Wearers

A microscopic parasite found in water and soil is causing permanent vision loss in contact lens wearers, with 85% to 95% of acanthamoeba keratitis cases affecting people who wear contacts. This rare but devastating infection occurs when the single-celled organism burrows into the cornea, using it as a food source and potentially causing blindness.

Teresa Sanchez learned this the hard way during a medical trip to Mexico nearly four years ago. What started as a dry, poking sensation in her right eye turned into months of excruciating pain and permanent vision damage. "I couldn't have my blinds open in my room, because that would trigger really, really bad pain in my eye," said Sanchez, 33, from Las Vegas.

What Makes This Parasite So Dangerous?

Acanthamoeba keratitis affects over 23,000 people worldwide annually, according to 2023 data from 20 countries including the United States. The parasite, called acanthamoeba, doesn't need a host to survive and thrives in water sources where contact lens wearers might expose themselves.

"It basically uses the cornea as its food source, and that causes inflammation and tissue damage and then can eventually cause permanent loss of vision," said Dr. Paul Barney, an optometric physician and center director of the Pacific Cataract and Laser Institute in Anchorage, Alaska.

Contact lenses create perfect conditions for infection by causing tiny breaks in the corneal epithelium - the eye's protective barrier layer. The parasite can hitch a ride on lens surfaces or become trapped between the contact and the eye, making it easier to burrow deeper into the cornea.

Why Are So Many Cases Being Missed?

The rarity of acanthamoeba keratitis means many eye care professionals don't recognize it, leading to dangerous misdiagnoses. Grace Jamison, a 20-year-old woman, developed the infection in both eyes after showering with contacts while in the Dominican Republic. Her optometrist initially prescribed steroid drops, which made her condition worse.

"When I was completely blind in both of my eyes, I regretted not taking advantage of how I could see before," Jamison said. She remained blind for about two months before receiving proper treatment.

Common symptoms that doctors often mistake for other conditions include:

• Pain and Light Sensitivity: Intense burning pain that can radiate throughout the head, along with extreme sensitivity to light
• Vision Problems: Blurred or obscured vision that progressively worsens without proper treatment
• Eye Irritation: Redness, dryness, excessive tears, and the sensation of having something foreign in the eye

The most common misdiagnosis is herpes simplex keratitis, and in early stages, the infection can even appear like pink eye. Sanchez was initially treated for both viral and bacterial pink eye before doctors identified the real culprit.

How Can Contact Lens Wearers Protect Themselves?

The Contact Lens Society of America emphasizes that contact lenses are medical devices requiring strict hygiene protocols, including avoiding water contact while swimming, showering, or sleeping. However, many contact lens wearers report never being warned about these risks by their eye care providers.

Treatment for acanthamoeba keratitis can take months to years and requires aggressive intervention. The parasite's extraordinary resilience makes it highly resistant to standard treatments, and some patients may need cornea transplants to restore vision.

"It can be quite devastating if it's not diagnosed promptly and treated aggressively," Barney noted, emphasizing the importance of working closely with eye care professionals and following their guidance throughout the lengthy treatment process.