Acanthamoeba Keratitis: Symptoms, Causes, and Treatment

Although rare, Acanthamoeba keratitis can have devastating effects if left untreated. The condition is an eye infection that is caused by microscopic organisms typically found in lake water and soil; however, the organisms can also colonize in swimming pools, hot tubs, and even drinking water. While many people are exposed to the organisms, few actually develop the infection as they often wash the bacteria off before an issue occurs. Nonetheless, it is important to be aware of the symptoms and risks associated with the condition to avoid a life-altering infection.

What Is Acanthamoeba Keratitis?

A rare but serious eye infection, Acanthamoeba keratitis can cause permanent visual impairment or even blindness if left untreated. The infection is caused by a microscopic free-living single- celled organism known as Acanthamoeba. The condition was first recognized in 1973, with a more recent outbreak reported in 2007 by the US Food and Drug Administration.

The amoeba causes Acanthamoeba keratitis when it attaches to and infects the transparent outer covering of the eye known as the cornea. The Acanthamoeba amoebas are actually very common in nature. They are often identified in such locales as lakes, oceans, soil, and even the air. As such, most people come into contact with them without ever even knowing it. Even with this frequency of exposure, the occurrence of the infection is still low; most people rinse off the organism before it has a chance to infect the body.

The actual infection typically occurs when the amoebas enter the body through a cut or other eye trauma, from contaminated water, or as a result of poor eye hygiene. In any case, the condition is typically characterized by pain that is out of proportion to the current state of the eye.

Several factors might put you at more risk for developing the condition. If you wear contact lenses, are exposed to the organism through contaminated water, or have corneal trauma, it is more likely that you’ll contract the infection. In fact, one study found that 75 percent of individuals treated for the condition were contact lens wearers.

Symptoms of Acanthamoeba Keratitis

The symptoms of Acanthamoeba keratitis often mimic that of other eye infections. This imitation complicates diagnosis of the condition and makes it particularly important that you contact your doctor as soon as you suspect you may have any type of eye infection. Identifying the infection early and starting treatment as soon as possible is important to reduce your risk of more progressive long-term effects of the condition. Symptoms of the condition can last for several weeks or even months and may include:

• Eye pain;
• Eye redness;
• Blurry vision;
• Light sensitivity;
• Sensation of something in your eye;
• Excessive tearing.

If you begin experiencing any of these symptoms, you should contact your eye doctor immediately. Acanthamoeba keratitis will eventually develop into severe pain and/or permanent vision loss or blindness if not treated appropriately.

Causes of Acanthamoeba Keratitis

Acanthamoeba keratitis is caused by the free-living single-celled Acanthamoeba infecting the outer layer of the eye. While anyone can develop the condition, it is much more prevalent in contact lens wearers and/or those who practice poor eye hygiene. As such, you can drastically reduce your risk of contracting the condition by following certain guidelines outlined by studied eye health professionals.

To reduce your risk of infection:

• Visit your eye care professional for eye examinations regularly;
• Replace contact lenses according to the schedule specified by your eye care provider;
• Remove your lenses prior to engaging in any activity involving water, including showering, swimming, or using a hot tub;
• Wash your hands with soap and warm water and dry with a clean cloth before handling your contact lenses;
• Regularly clean your lenses following the instructions provided by your eye care professional and/or the manufacturer of your lenses;
• Use fresh cleaning or disinfecting solution to cleanse your lenses each time before you store them;
• Clean, rub, and rinse your lenses each time you remove them;
• Store reusable lenses in the appropriate case;
• Sanitize lens storage cases after each use and replace them once every three months.

Acanthamoeba Keratitis Treatment

Early detection of the infection is essential for effective treatment, otherwise serious vision impairment and even blindness can occur. This infection is notably difficult to treat due to the resiliency of the amoeba itself.

The first step toward treatment is an accurate diagnosis of the condition itself. In most cases, diagnosis involves a high degree of suspicion, particularly if the patient is a contact lens wearer. Beyond that, diagnosis is typically made based on clinical picture and a collection of the organisms from a corneal culture. It is important to note, though, a negative culture does not necessarily rule out the infection. Microscopy of the eye may also be used to assist in diagnosis.

At any rate, current treatment regimens typically involve the application of a topical cationic antiseptic, such as polyhexamethylene biguanide or chlorhexidine. This treatment is generally used in combination with a diamidine, such as propamidine or hexamidine.

The duration of treatment may range anywhere from six months to a year. Therapy may also involve a topical cyclopegic solution and oral nonsteroidal medication to control the pain commonly associated with the condition.

The use of corticosteroids to reduce inflammation is currently not widely used in treatment, as research is inconclusive of the benefits of this treatment to this point. Penetration keratoplasty, however, may help restore visual acuity if vision impairment has already occurred.

Summing Up

While Acanthamoeba keratitis is a potential life-altering eye infection, it can often be effectively prevented with good eye hygiene, regular eye exams, and safe water exposure. If you do, however, contract this infection or another, early identification is key in effective treatment.

You should seek your doctor’s care if you begin experiencing eye pain, redness, sensitivity, tearing, or vision changes, as these could be signs of Acanthamoeba keratitis or another eye infection. Contact lens wearers are at the highest risk for this condition. However, most people are exposed to the organism that causes the condition at some point, so it is important for everyone to be aware of the issue.