Acanthamoeba keratitis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 3, 2016
StartDiseasesAcanthamoeba keratitis

Acanthamoeba keratitis refers to a rare eye infection that can lead to devastating complications, such as the loss of the eye or blindness. This infection is caused by microscopic organisms that are found in water and soil. While many people are exposed to the organisms, few will actually become infected by them.


Definition & Facts

Acanthamoeba keratitis is a rare but serious condition that can cause significant impairment to the vision and eye structure. The infection is caused by a minuscule, free-living amoeba called Acanthamoeba. This microorganism infects the transparent outer covering of the eyeball, known as the cornea.

Acanthamoeba amoebas are extremely common in nature and can be found in bodies of water, soil, and air. The microorganisms are also common to swimming pools, hot tubs, and even drinking water. One of the best defenses against the condition is maintaining proper eye hygiene which includes taking proper care of one's contact lenses.

Symptoms & Complaints

It can sometimes be difficult to get a definitive diagnosis of Acanthamoeba keratitis because the symptoms of the condition actually mimic several other common eye infection. Nevertheless, symptoms of this condition may last several weeks to months and include:

It is important that patients not ignore any of the above symptoms. If left untreated, the condition can cause severe pain, vision loss, and blindness. Patients should consult their eye doctor as soon as possible if they begin experiencing the above symptoms.


The infection is caused by the common microorganism Acanthamoeba. People are exposed to the microorganism in the environment regularly, as it is prevalent in water and soil. The microorganism can also be found in pool water, hot tubs, and other public areas. It typically enters the body through a physical opening, such as a minor abrasion or cut.

While anyone can develop the infection, poor eye hygiene can significantly increase an individual’s likelihood of contracting the condition. The use of contact lenses may allow Acanthamoeba directly to enter the eye and promote infection due to trauma to the cornea, and this condition is most common in people who wear contact lenses. For those individuals who do wear contact lenses, certain habits can increase the risk of contracting the infection:

  • Storing and handling lenses improperly
  • Disinfecting lenses improperly, such as using tap water or homemade solutions
  • Swimming, using a hot tub, or showering while wearing lenses
  • Coming into contact with contaminated water
  • Having a history of trauma to the cornea

Diagnosis & Tests

Early diagnosis is crucial for effective treatment of Acanthamoeba keratitis. The infection is diagnosed using observation as well as laboratory testing. An eye care provider will assess symptoms as well as longevity of symptoms. Likewise, the healthcare professional will also conduct a scraping to determine the presence of the Acanthamoeba amoeba in the eye. Diagnosis of this condition is most accurate when it consists of a confocal microscopy and superficial corneal scraping.

Treatment & Therapy

The earlier the infection is caught, the better the chances are for effective treatment. However, it can be difficult to treat due to the resiliency of the microorganism that causes it. The duration of treatment may last anywhere from six months to a full year.

Treatment regimens include regular application of an antiseptic agent, such as polyhexamethylene biguanide, propamidine, or hexamidine. Treatment also involves managing symptoms of the condition. Corticosteroids may also be used to manage inflammation. There are a few innovative treatments that have been found to help restore visual acuity as well.

Prevention & Prophylaxis

While treatment is typically effective if the condition is caught early enough, the best step toward managing the health of the eyes is prevention. Individuals can reduce their risk of contracting common eye infections as well as Acanthamoeba keratitis by:

  • Making regular visits to an eye care provider for checkups and examination.
  • Following the prescribed schedule and replacing contact lenses as indicated by the eye care provider.
  • Removing contact lenses prior to participating in any activity involving contact with water, including showering, swimming, and/or using a hot tub.
  • Washing hands with soap and warm water and drying with a clean towel before handling contact lenses.

Cleaning contact lenses according to instructions indicated by the eye care provider and the manufacturer is crucial for preventing eye infections including Acanthamoeba keratitis. In most cases that involves:

  • Always using fresh cleaning and disinfecting solution each time lenses are cleaned and stored. Old solution should never be reused.
  • Using an approved solution for disinfecting lenses. One should not use rewetting drops to disinfect lenses, as neither solution is effective for disinfecting.
  • Cleaning, rubbing, and rinsing lenses each time you remove them from them from your eyes. Rubbing and rinsing your lenses will assist in removing harmful microbes and residues.
  • Storing reusable lenses in an appropriate case and taking necessary measures to disinfect the case as necessary.
  • Rubbing and rinsing storage case with sterile contact lens solution (not tap water), emptying it, and leaving it open to dry after each use.
  • Replacing cases at least once every three months.

Contact lens wearers should also consult their eye care providers to determine what solution is best. Likewise, any individual, especially contact lens wearers, should also consult their eye care providers if they experience any of the following symptoms: eye redness or pain, blurred vision, sensitivity to light, feeling of something in the eye, or excessive tearing.

Although Acanthamoeba is a common microorganism, the eye infection it can cause is relatively rare. In any case, though, proper eye care techniques and maintaining effective eye hygiene is important to reduce one’s risk of this and other eye infections. Early diagnosis and swift treatment is important to prevent major complications associated with Acanthamoeba keratitis.