An Overview of Acanthamoeba Keratitis

Medically Reviewed By William C. Lloyd III, MD, FACS
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Acanthamoeba keratitis (AK) is a rare eye infection that occurs when a single-celled organism called Acanthamoeba infects the cornea. While the condition can be serious, seeking prompt treatment and taking steps to avoid reinfection can help prevent complications. This article discusses Acanthamoeba keratitis and its causes, symptoms, diagnosis, and treatments. It also covers the risk factors and how to prevent the condition.

What causes Acanthamoeba keratitis?

A woman putting in her contact lenses
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AK develops when Acanthamoeba infects the cornea, which is the transparent outer layer of the eye. Acanthamoeba is an amoeba, or single-celled organism, commonly existing in soil and bodies of water like ponds or swimming pools.

AK is most common among people who wear contact lenses without regular cleaning or maintenance. Infrequently cleaned contact lenses can trap debris against the eye. This makes it more likely that organisms in the debris will penetrate the corneal surface and infect the eye.

Acanthamoeba initially adheres to the surface of the cornea and can then penetrate deeper into the eye. This can lead to extensive damage and potential vision loss.

Learn more about the types of keratitis.

What are the symptoms of Acanthamoeba keratitis?

The symptoms of AK may include:

While symptoms are typically confined to one eye, it’s possible for both eyes to be affected.

Without treatment, the pain may become severe and vision loss may occur.

Learn more about when to contact a doctor for eye infections.

How do doctors diagnose Acanthamoeba keratitis?

To diagnose AK, an eye specialist will ask you about your symptoms and history. They may be able to see Acanthamoeba in your cornea with confocal microscopy, which allows doctors to closely examine the eye.

In addition, the specialist can take scrapings from the cornea or samples from your contact lens case and cleaning solution. Analysis of these samples may reveal the presence of the organism.

Because the symptoms of AK can resemble other eye infections, initial misdiagnosis is common. Because delaying treatment can lead to serious complications, it’s essential to tell your doctor about your eye history and contact lens habits.

What are the treatments for Acanthamoeba keratitis?

Treatment for AK can include one or more prescription medications applied topically to the eye.

A common first-line treatment uses classes of antiamoebic drugs, which destroy amoebas. Diamidines and biguanides, when given together, can be effective in clearing up AK. These medications are prescribed as eye drops or ointments.

Treatment can last for months, going from an hourly schedule day and night to an hourly schedule only during the day. The frequency may further decrease throughout the course of the treatment.

Other medications that may be used alongside diamidines and biguanides can include:

  • neomycin (Neo-Fradin) to prevent accompanying bacterial infections
  • miltefosine (Impavido) for treatment-resistant AK
  • antifungal drugs, such as posaconazole (Noxafil) and voriconazole (Vfend)

If topical treatments are ineffective, surgery may be necessary. This may involve a corneal transplant, also called penetrating keratoplasty.

Learn more about corneal transplant success rates.

What is the outlook for people with Acanthamoeba keratitis?

The outlook for people with AK may be improved with an accurate, prompt diagnosis and treatment. When treatment begins within 3 weeks of the first appearance of symptoms, the outcomes are generally much better.

Promptly reporting symptoms and closely following your doctor’s treatment plan is the best way to improve your outlook.

What are some potential complications of Acanthamoeba keratitis?

Delaying or failing to seek treatment for AK can lead to severe complications, including:

  • glaucoma
  • atrophy of the iris, the colored part of the eye that surrounds the pupil
  • cataracts
  • corneal ulceration leading to perforation
  • long-term damage to the cornea
  • vision loss or blindness

What are the risk factors for Acanthamoeba keratitis?

While anyone can develop the condition, people who wear contact lenses have an increased risk of AK. In addition, a 2022 study suggests that people who use reusable contact lenses are around three times more likely to develop AK than people who use daily disposable contact lenses.

The same study notes that certain actions could also increase the risk of AK, such as wearing contact lenses in the shower or overnight.

Additionally, damage to the cornea and exposure to contaminated water may predispose you to the condition.

Can you prevent Acanthamoeba keratitis?

Preventing AK primarily consists of modifying or avoiding the risk factors associated with the condition. This may involve:

  • only using daily disposable contact lenses
  • avoiding sleeping, showering, or swimming in your contact lenses
  • wearing, cleaning, and storing contact lenses as directed by your eye doctor
  • washing your hands thoroughly with soap and water before handling your contact lenses
  • wearing protective eyewear if you are frequently exposed to soil or potentially contaminated water

Other frequently asked questions

William C. Lloyd, III, M.D., FACS, has reviewed the answers to these common questions about AK.

Can Acanthamoeba keratitis be cured?

Yes, AK can be cured. However, it’s essential to follow your doctor’s treatment plan as closely as possible. Completely eliminating the infection can take months.

What are the chances of getting Acanthamoeba keratitis?

While the overall chances of AK are low, people who wear contact lenses have an increased risk. This is especially true without regular contact lens maintenance and hygiene. Using daily disposable lenses and avoiding contact with contaminated water or soil may decrease your risk.

Can you get Acanthamoeba from tap water?

Yes, Acanthamoeba may exist in tap water. Rinsing your contact lenses in tap water can increase your likelihood of developing AK.

Is Acanthamoeba keratitis painful?

Yes, AK can be painful. As the condition worsens, the pain may become severe, and partial or total vision loss may occur.


AK is a rare but potentially serious condition. While anyone can develop it, it’s most common in people who wear contact lenses. Prompt diagnosis and appropriate antimicrobial treatment can cure the infection and restore vision.

Talk with your eye doctor about ways to manage and prevent AK.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2023 Jan 30
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  2. Fanselow, N., et al. (2021). Acanthamoeba keratitis, pathology, diagnosis and treatment.
  3. Somani, S. N., et al. (2022). Acanthamoeba keratitis.
  4. Szentmáry, N., et al. (2018). Acanthamoeba keratitis – Clinical signs, differential diagnosis and treatment.