What is acanthamoeba?
Acanthamoeba keratitis is a serious sight-threatening eye infection affecting the cornea, the clear front surface of the eye. The majority of cases occur in contact lens wearers. Acanthamoeba is a small single-celled organism that is very widespread throughout the environment, especially where there is standing water, and it may be present in poorly treated tap water. Acanthamoeba exists in two forms:
- trophozoite, the active form that feeds, moves, and reproduces, and is easier to kill
- cyst, a dormant form that is much harder to destroy
Acanthamoeba can change between these two forms, depending on whether it is in a favourable or a hostile environment.
Acanthamoeba is normally harmless to humans, but if it is transferred to the eye on a contaminated contact lens it can infect the cornea (the clear window at the front of the eye). Such infections can be difficult to treat. Prevention is very important. This includes good contact lens hygiene, especially avoiding tap water touching contact lenses or lens cases.
Patients with early Acanthamoeba keratitis usually complain of discomfort, redness and light sensitivity of the affected eye. In the later stages the eye can become very painful as the nerves and deeper parts of the cornea become affected.
How is acanthamoeba keratitis managed?
An optometrist who suspects this infection should immediately refer the patient as an emergency (same day) to an ophthalmologist (specialist eye doctor), who will try to confirm the diagnosis and then prescribe special eye drops given day and night. Often the patient will be admitted to hospital. If there is much scarring of the cornea following the eventual elimination of the infection, and vision is badly affected, a corneal transplant may be recommended.
