Acanthamoeba keratitis is a rare parasitic eye infection. It is usually caused by A. polyphagia, and A. castellanii, two of the eight known free-living and microscopic Acanthamoeba species. The condition is primarily seen in those who wear contact lenses, causing severe pain and a ring-shaped stromal infiltration in the eye. If left unchecked for a long time, Acanthamoeba keratitis may lead to visual impairment in varying degrees and even permanent blindness.

Causes
Acanthamoeba keratitis, mainly observed in contact lens wearers, occurs when the cornea is inflamed due to infection by Acanthamoeba, a single-celled organism. The following practices are known to increase one’s susceptibility to the disease:

• Poor disinfection of lenses using homemade solutions
• Using tap water for cleaning the lenses, including the case
• Swimming with contact lenses on, particularly in rivers and freshwater lakes
• Not following proper contact lens care protocol
• Improper handling and storage of the lenses
• Contact with contaminated water
• Injury, trauma, or similar damage to the cornea history

Symptoms
The symptoms manifest several days or weeks after the parasite infection. The common indications include the following:

• Pain in the eye that does not go away with traditional treatment methods
• Redness in the eye for a long time
• Vision that gets blurred all of a sudden without a particular reason
• Increased or abnormal sensitivity to light (known as photophobia)
• The feeling of having a foreign object stuck in the eye
• Tearing up excessively
• Vision that has decreased comparatively in a short period
• Discharge from eyes

Those who experience these signs should visit a healthcare provider for a diagnosis.

Diagnosis
Ophthalmologists (eye doctors) perform eye examinations to assess the condition and may suggest the following tests to confirm Acanthamoeba keratitis:

• Superficial keratectomy
  In this procedure, the healthcare expert scrapes off some cells from the corneal surface after numbing the area. The cells are studied under a microscope to check for the presence of Acanthamoeba species.
• Confocal microscopy
  In this test, laser light is used to generate detailed pictures of the corneal layers. The doctor then examines the images for the presence of Acanthamoeba.

Treatment and management
Acanthamoeba keratitis can be treated surgically or sun-surgically. The following are the main approaches healthcare practitioners use to treat patients with this rare disease:

• Topical solutions
  The most common treatment is the application of solutions over the infected eye surface to kill harmful microorganisms. The treatment is recommended for months or even a year.
• Surgery
  In cases of severe infections, the doctor may remove the damaged tissues through surgery. If the condition worsens, the healthcare provider might suggest a penetrating keratoplasty that involves the transplantation of a full-thickness cornea. A cornea from a suitable donor is used to replace the damaged one in the patient.

Acanthamoeba keratitis is not common in our country. Only one to two per million contact lens users get this disease. Left untreated, it can lead to more severe conditions like uveitis, cataracts, scleritis, and secondary glaucoma. Therefore, patients should immediately consult a doctor when the symptoms appear and receive proper treatment.