acanthamoeba keratitis
What is Acanthamoeba Keratitis?
Acanthamoeba keratitis (AK), is a devastating, extremely painful eye infection that affects the cornea (the window of the eye). It is mainly found in association with contact lens wearers with specific behaviours, putting these people more at risk – although there are cases of this disease in non-contact lens users. AK can lead to severe vision loss with around 50% of patients needing corneal transplantation or becoming blind, and for around 5-10% of patients can also result in enucleation (removal) of the eye. AK is frequently misdiagnosed, and the associated pain can be widely underestimated by various clinicians.
AK is often characterized by pain out of proportion and the late clinical appearance of a stromal ring-shaped infiltrate. This condition is both difficult to diagnose and difficult to treat therapeutically and almost always needs some sort of surgical intervention.
AK can affect one eye (unilateral) or both eyes (bilateral). A rare and painful complication of AK is Acanthamoeba scleritis also known as ASK, which affects around 10–18% of patients. In extreme cases the Acanthamoeba can cause a systemic infection beyond the eye, even causing granulomatous Acanthamoeba encephalitis (GAE) of the brain.
Acanthamoeba is suspected to cause pathology through using small cuts or abrasions in the cornea to invade the eye. This is probably due to some trauma to the eye and exacerbated by wearing contact lenses, and the parasite takes advantage of these factors, using the natural bacteria found on the surface of the eye as a food source.
This picture shows the different layers of a cornea with AK (reaction of the parasite)
Figure: Acanthamoeba can enter the eye by attaching to contact lenses (1), the depleted immune activity allows binding to the epithelial layer (2) and the amoeba can begin to feed on the epithelial cells (3). Micro-abrasions on the epithelial layer provides an opportunity for the amoeba to access the Bowman’s membrane and stroma of the patient (4). Drug pressure can instigate encystation of the parasite (5) which can then begin reinfection upon removal of this pressure (6).
AK can lead to severe vision loss with around 50% of patients becoming blind, need corneal transplantation, and can also result in enucleation of the eye for 5-10% of patients. AK is frequently misdiagnosed and the associated pain is underestimated by various clinicians.
AK is often characterized by pain out of proportion to findings and the late clinical appearance of a stromal ring-shaped infiltrate. This disease is both difficult to diagnose and difficult to treat therapeutically and almost always needs some sort of surgical intervention.
AK can affect one eye (unilateral) or both eyes (bilateral). A rare and painful complication of AK is Acanthamoeba scleritis also known as ASK, which affects ~10–18% of patients. In extreme cases the Acanthamoeba can cause a systemic infection beyond the eye, even causing granulomatous Acanthamoeba encephalitis (GAE) of the brain.
The way the acanthamoeba works is using small cuts or abrasions in the cornea to invade the eye, probably due to wearing contact lenses or trauma to the eye, by taking advantage of that while using the bacteria on the eye as food.
What is the cycle of Acanthamoeba
TROPHOZOITE
Trophozoite – also referred amongst AK Warriors as the active stage – is when the parasite feeds, grows and replicates itself. This is when you might experience a lot of pain, light sensitivity and/or sometimes a deterioration in vision.

“Images A and B 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).”
CYST
Cyst – also known amongst AK Warriors as the passive stage – is when the amoeba is dormant and does not show much activity, in other words has gone into hibernation (forms a protective wall to protect itself) being able to survive for long periods of time. Unfortunately, one cannot predict when they will become active again.
“Images A and B 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).”
What are the symptoms?
Symptoms vary, so as we always recommend, if you are a contact lens user and have been in contact with water and your eye is feeling “different”, then:
- take your contact lenses out!
- get your eye checked by an eye professional as soon as possible!
- don’t forget to tell them that you are a contact lens user and have been in contact with water.
If available, advocate for an early confocal scan! Time is of essence.
Symptoms:
- A Foreign body sensation – feeling like something is in the eye
- Mild to extreme light sensitivity also called photophobia
- Inability to wear contact lens
- Irritation or grittiness
- Blurred vision
- Partial or total vision loss
- Red eye
- Watery eyes
- Aching to excruciating eye pain
- Headache
Contraction risks and how to prevent?
AK is caused by a free-living amoeba (parasite) that is typically found in soil, bodies of water and tap water; so, showering, bathing, swimming in pools, lakes, ponds, oceans, bathtubs, and even rinsing contact lenses or cases with tap water can put you at risk.
If you are a contact lens wearer, never let water come in contact with your contact lenses!
For more information Contact Lens User

- Water and Contact Lenses don’t mix
- Never use water to store your contact lenses
- Never shower wearing your contact lenses
- Never swim wearing your contact lenses
- Never use a hot tub or a sauna wearing your contact lenses
- Never use anyone else’s contact lenses or casing
- Never sleep wearing your contact lenses
- Replace your contact lenses according to your eye health professional.
Is Acanthamoeba Keratitis misdiagnosed?
%
Misdiagnosed
When it comes to misdiagnosis, sadly we are seeing that around 80% of AK Warriors are being isdiagnosed, worldwide, with either other bacterial, viral, or fungal pathogens.
From that statistic more than 50% were misdiagnosed with herpes simplex meaning corticoids and steroids were initially administered – making the situation and infection worse. There are similarities within each of these infections, but the treatments are completely different.
%
Herpes Simplex virus
Estimated numbers with Acanthamoeba Keratitis
AK is increasing and should be recognized as a severe sight-threatening ocular infection, worldwide.
With more people wearing contact lenses for general convenience, sport activities, Halloween decoration, social media influencing eye colour, trends and phases, the number of potential exposures to Acanthamoeba and obtaining keratitis is increased.
With an estimate of more than 140 million contact lens users worldwide, and a risk between 17 – 70 cases per million; we are talking about an average of 5000 contact lens users contracting Acanthamoeba Keratitis per year.

Possible Aftermath
Based on AK Warriors’ experience possible common symptoms and/or lasting effects:
Trigeminal nerve pain
Cataract
Dry eye
Medical PTSD
Severe eye inflammation
Glaucoma/intra-ocular pressure
Limbal stem cell damage
Extreme high or extreme low eye pressure
Retinal detachment
Liver problems due to medication
Mouth/tooth problems due to steroid use
Optic nerve damage
Corneal perforation
Loss of vision
Loss of eye
Iris irregularity (atrophy, dyscoria, corectopia, or synechiae)
Charles Bonnet Syndrome
Neovascularization (new blood vessel growth)