Acanthamoeba Keratitis (AK)

Is a serious and severe eye infection that can cause excruciating pain and damage the cornea, potentially leading to vision loss, blindness or loss of the eye.

When diagnosed early, AK can be treated effectively, often resulting in favorable outcomes. The harm done to the cornea may have a minor effect on vision, with scarring potentially being minimal. People with AK need to cultivate patience and resilience as they face the challenges of recovery.

One of the most concerning aspects of AK is the potential for severe vision loss.

Acanthamoeba causes 5% of corneal infections worldwide. Yet is disproportionately responsible for over 50% of cases resulting in vision loss. One quarter of these patients lose 75% of their vision after the condition has resolved.

In fact, approximately 41% of AK cases eventually require a corneal surgery or even become blind. Most cases are unilateral (affecting one eye) while 4% to 11% are bilateral (affecting both eyes). Tragically, AK has a high enucleation rate of 6%. Some AK patients choose to have the affected eye removed.

Because contact lens wearers are at increased risk of developing AK, it is essential to educate them clearly about the serious consequences they may face through improper handling or care of their lenses.

Image Source: Scanning electron micrograph (SEM) of two Acanthamoeba trophozoites approaching an indent in a contact lens, © Fiona L Henriquez, Adam Hammerschmid. University of the West of Scotland (UWS), U.K

The life cycle of Acanthamoeba is typically divided into two stages:

Images of a Trophozoite –  supplied and used with permission from Dr. Christopher A. Rice (Purdue University). Preparation of cells and Scanning Electron Microscopy (SEM) imaging of amoeba was performed by A. Cassiopeia “Cassie” Russell (University of Georgia) on Dr. Peter Bush’s Field Emission Scanning Electron Microscope (FESEM) with Oxford Energy-dispersive X-ray Spectrometer (EDS) – Hitachi SU70 (University at Buffalo)

Images of a Cyst –  supplied and used with permission from Dr. Christopher A. Rice (Purdue University). Preparation of cells and Scanning Electron Microscopy (SEM) imaging of amoeba was performed by A. Cassiopeia “Cassie” Russell (University of Georgia) on Dr. Peter Bush’s Field Emission Scanning Electron Microscope (FESEM) with Oxford Energy-dispersive X-ray Spectrometer (EDS) – Hitachi SU70 (University at Buffalo)

Treating AK requires a careful balance; the treatment must be sufficiently toxic to eliminate the trophozoites and the cysts while preserving the strength of the corneal cells.

Contact lens wearers are particularly susceptible to AK because contact lenses can cause small defects on the cornea, absorb water, or trap the parasite, which is found in any country in the world. Therefore, it is crucial to never let water touch your contact lenses. In addition, it is important to follow proper contact lens hygiene and handling to further reduce the risk of AK infection.

If you suspect that you may have AK, it is crucial to take out your contact lenses and seek medical attention without delay.

Unfortunately, when it comes to correctly diagnosing AK, statistics show that around 75% to 90 % of AK patients are being misdiagnosed with herpes, bacterial, viral or fungal pathogens, amongst others. More worryingly,  48% of the misdiagnosed AK cases are herpes simplex, which can lead to the administration of corticosteroids and steroids, making the infection worse and leading to a poorer outcome. Another 25,2 % as fungal infection and 3,9% are mistaken as bacterial infection.

The symptoms may be similar to other infections. However, the treatment is very different. It is vital that the correct diagnosis of AK is made quickly. Due to misdiagnosis, it can take days, weeks, months or even over a year to detect AK, during which time the amoeba can continue to multiply or hide deeper in the cornea.

Despite the disturbing symptoms the first priority in treating AK is to eradicate the parasite. The cornea specialist will prescribe anti amoebic eye drops to attack the amoeba along with other helpful eye drops and oral medication.

The initial phase of treatment involves using the drops every hour 24/7.

In the second phase these eye drops are used during waking hours. The duration of this whole process depends on the severity of the infection, the availability of the drugs and the experience of the specialist. This can take from six months up to one year or even longer. However, in some cases, the medication may be stopped to see how the eye responds. If the infection flares up again, the treatment can be restarted.

Once the amoeba has been eradicated, the specialist’s next priority is to help restore vision. This may include cataract surgery, corneal transplants, and other procedures. From clear sight to loss of vision or removal of the eye, the outcome of treatment varies widely.

The journey is characterized by many ups and downs, an intense drop regime, excruciating pain and many eye appointments, leaving little space for daily life. AK affects not only the eye, but also the mental and emotional health of the patient.

Patients need to take extra care of their eyes to prevent further damage or re-infection after treatment for AK.

It is likely that the patient will need to continue to use eye drops or other medications for several months or even years after the initial infection. The doctor may also recommend wearing special contact lenses or glasses to protect the eyes.

Unfortunately, AK can still have serious effects even after the infection has been treated. Some people may experience long-term or permanent damage, which could include vision loss, blindness or, in rare cases, the need for removal of the eye.

It is also important to note that the disease itself, as well as the oral medications used in treatment, can lead to additional issues, such as trigeminal nerve pain, dental problems, stomach issues, or elevated liver and kidney levels.

Regular blood tests are essential when taking oral medications for AK treatment. These tests help to monitor liver and kidney function to detect any potential side effects early. You can reduce the risk of serious complications and ensure your overall safety during treatment by being proactive about your blood counts, allowing your healthcare provider to make any necessary adjustments to keep you safe.

Many AK patients also experience psychological trauma (medical PTSD) and may need professional support to help them cope with these challenges.

Worldwide Acanthamoeba is widely prevalent in water sources like oceans, lakes, rivers, swimming pools, tap water and even bottled water. The increased use of contact lenses for convenience, sports, costumes, and social media trends is contributing to a higher risk of developing AK.

Contact lens wearers are often unaware of the risk associated with wearing contact lenses while sleeping, showering, swimming or participating in water sports.

Two recent studies reveal an estimated incidence of 2.34 – 2.9 AK cases per million globally, resulting in around 19.000 – 24.000 new infections each year based on the UN’s 2024 world population estimate of 8.1 billion. However, infection rates vary from country to country, with the UK, Portugal, Egypt, India and New Zealand having the highest per capita numbers, followed by Canada, the Netherlands, Italy, Singapore and Australia.

Image source: The estimated annual incidence of Acanthamoeba keratitis by regions (as defined by the UN). The figure used with permission from co-author Xu. Source: Yuheng Zhang, Xizhan Xu, Zhenyu Wei, Kai Cao, Zijun Zhang, Qingfeng Liang, The global epidemiology and clinical diagnosis of Acanthamoeba keratitis