Acanthamoeba Keratitis: A Rare But Serious Eye Infection

Acanthamoeba keratitis (AK) is a rare but potentially vision-threatening infection of the cornea—the clear, dome-shaped surface at the front of the eye. While uncommon, it can lead to significant pain, prolonged treatment, and, in severe cases, permanent vision loss if not diagnosed and treated promptly. Contact lens wearers, including scleral lens wearers, make up the majority of cases. It is more likely to affect you if you have an eye infection, a corneal scratch or other eye injury, or are immunocompromised. Eye injuries can leave the cornea more vulnerable, allowing the parasite to enter the cornea.

What Is Acanthamoeba?

Acanthamoeba is a microscopic, free-living amoeba commonly found in the environment, including tap water, lakes, hot tubs, swimming pools, soil, and air. In most situations, it poses no threat to human health. However, when it comes into contact with the eye—particularly a cornea that has been compromised—it can cause a serious infection.

Who Is at Risk?

Although anyone can develop Acanthamoeba keratitis, the majority of cases occur in contact lens wearers. Risk factors include:

Rinsing or storing contact lenses in tap water
Swimming, showering, or using hot tubs while wearing contact lenses
Improper contact lens cleaning or storage
Using homemade or non-sterile saline solutions
Poor contact lens hygiene or overwearing lenses

Even individuals who follow recommended lens care practices can be at risk, which makes awareness and early detection especially important.

Symptoms to Watch For

Acanthamoeba keratitis often begins with symptoms that resemble more common eye infections, which can delay diagnosis. Key symptoms may include:

Severe eye pain
Redness and tearing
Sensitivity to light (photophobia)
Blurred or decreased vision
A feeling of something in the eye
Excessive tearing or discharge

Because symptoms can worsen over time, early evaluation by an eye care professional is critical if they persist or intensify.

Why Early Diagnosis Matters

AK is difficult to diagnose and treat, and delayed diagnosis increases the risk of corneal scarring, the need for corneal transplantation, and long-term vision impairment. Diagnosis may involve corneal scraping, specialized cultures, confocal microscopy, or advanced imaging techniques. Once identified, treatment often requires a prolonged course of topical antimicrobial medications and close monitoring.

Treatment and Recovery

Treatment for Acanthamoeba keratitis can be lengthy—often lasting several months—and may involve:

Topical anti-amoebic medications
Pain management strategies
Temporary discontinuation of contact lens wear
In severe cases, surgical intervention such as corneal transplantation

Recovery varies widely. Some patients regain good vision, while others may experience lasting visual effects despite aggressive treatment. AK can result in permanent scarring, permanent corneal irregularities, and/or vision loss. After the infection is completely cleared, scleral lenses, such as PROSE and BostonSightSCLERAL, may be an option to rehabilitate vision.