Acanthamoeba keratitis is a rare disease

Rare disease

A rare disease, also referred to as an orphan disease, is any disease that affects a small percentage of the population.Most rare diseases are genetic, and thus are present throughout the person's entire life, even if symptoms do not immediately appear...

 in which amoebae invade the cornea

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

 of the eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

.

Causes

In the United States, it is nearly always associated with contact lens

Contact lens

A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...

 use, as Acanthamoeba

Acanthamoeba

Acanthamoeba is a genus of amoebae, one of the most common protozoa in soil, and also frequently found in fresh water and other habitats. The cells are small, usually 15 to 35 μm in length and oval to triangular in shape when moving. The pseudopods form a clear hemispherical lobe at the anterior,...

can survive in the space between the lens and the eye. For this reason, contact lenses must be properly disinfected before wearing, and should be removed when swimming or surfing

Surfing

Surfing' is a surface water sport in which the surfer rides a surfboard on the crest and face of a wave which is carrying the surfer towards the shore...

.

However, elsewhere in the world, many cases of Acanthamoeba present in non-contact lens wearers.

Diagnosis

To detect Acanthamoeba on a contact lens in a laboratory

Laboratory

A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...

, a sheep blood agar plate with a layer (a lawn) of E. coli is made. Part of the contact lens is placed on the agar plate. If Acanthamoeba are present, they will ingest the bacteria, leaving a clear patch on the plate around the area of the lens. Polymerase chain reaction

Polymerase chain reaction

The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....

 can also be used to confirm a diagnosis of Acanthamoeba keratitis, especially when contact lenses are not involved. Acanthameoba is also characterized by a brawny edema and hazy view into the interior AC. Late stages of the disease also produces a ring shaped corneal ulcer.

Presentation

Signs and symptoms include severe pain, severe keratitis

Keratitis

Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...

 (similar to stromal herpetic disease), corneal perineuritis, ring ulcer (although this is late in the disease process)

Treatment

One treatment used is PHMB.

Propamidine isethionate has also shown some effectiveness.

Another possible agent is chlorhexidine.

Keratoplasty may sometimes be required.

A combined regimen of propamidine

Propamidine

Propamidine is an antiseptic and disinfectant.Propamidine isethinoate, the salt of propamidine with isethionic acid, is used in the treatment of Acanthamoeba infection....

, miconazole

Miconazole

Miconazole is an imidazole antifungal agent, developed by Janssen Pharmaceutica, commonly applied topically to the skin or to mucus membranes to cure fungal infections. It works by inhibiting the synthesis of ergosterol, a critical component of fungal cell membranes...

 nitrate, and neomycin

Neomycin

Neomycin is an aminoglycoside antibiotic that is found in many topical medications such as creams, ointments, and eyedrops. The discovery of Neomycin dates back to 1949. It was discovered in the lab of Selman Waksman, who was later awarded the Nobel Prize in Physiology and medicine in 1951...

 has also been suggested.

External links

• Acanthamoeba keratitis - Centers for Disease Control and Prevention
  Centers for Disease Control and Prevention
  The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
  
  
• Animal Planet - Monsters Inside Me: The Eye-Eating Parasite (video)
• BaHammam AS. Sleep from an Islamic perspective. Ann Thorac Med 2011;6:187-92