Acanthamoeba Keratitis

Causative agent

Acanthamoeba keratitis is an eye infection caused by microscopic amoeba. Several species of Acanthamoeba have been found to infect humans. In addition to eye infection which usually affects the cornea, Acanthamoeba could cause skin lesion or a systemic infection. It may also cause granulomatous amoebic encephalitis (GAE), an infection of the brain and spinal cord that typically occurs in persons with a compromised immune system.

Clinical features

People with Acanthamoeba keratitis may have eye pain, eye redness, blurred vision, sensitivity to light, foreign body sensation in the eye and excessive tearing or other eye symptoms. Untreated infection can cause permanent visual impairment or blindness, which requires corneal transplantation to regain vision. Therefore, early diagnosis is essential for effective treatment of Acanthamoeba keratitis.

Mode of transmission

Acanthamoeba species are commonly found in the environment worldwide, especially in soil and dust, in fresh water sources such as lakes, rivers and hot springs, and in hot tubs, swimming pools and spa facilities. Besides, it can be found in heating, ventilating and air conditioning systems, sewage systems and fresh water system (shower head and taps). Acanthamoeba is also found in contact lens tools.

Acanthamoeba keratitis primarily affects otherwise healthy people, most of whom wear contact lens, particularly when users have poor lens hygiene or when lenses are worn during swimming or other aquatic activities. Also, persons who have abrasion or injury to the cornea are at increased risk of infection.

No known cases of person-to-person spread of Acanthamoeba keratitis have been reported so far.

Incubation period

The incubation period for Acanthamoeba keratitis is unknown.

Management

Early diagnosis is essential for effective treatment of Acanthamoeba keratitis. If you have symptoms of Acanthamoeba keratitis, seek medical advice immediately.

Prevention

To prevent contact lens related microbial keratitis, contact lens wearers should take heed of the health advice below:

1. Regularly have your eyes checked by eye care professionals.
2. Remove the contact lens whenever you feel discomfort (e.g. redness, pain, tearing or blurred vision) and seek medical advice promptly if symptoms persist despite the contact lenses have been taken off.
3. Never share contact lenses.
4. When using contact lens solution, follow the manufacturer’s instructions for use.
5. Keep all accessories used for cleansing and disinfecting contact lenses (e.g. contact lens storage case) clean and replace them regularly.

To know more about contact lenses and tips on using contact lens solution, please refer to the following websites: https://www.mdd.gov.hk/filemanager/common/information-publication/Know%20More%20About%20Contact%20Lenses_Eng.pdf and https://www.mdd.gov.hk/filemanager/common/information-publication/Tips%20on%20Use%20of%20Contact%20Lens%20Solution.pdf