Acanthamoeba keratitis (AK) is an infection of the cornea, the clear ‘window’ at the front of the eye, that can be very painful. The infection is caused by a microscopic organism called acanthamoeba, which is common in nature and is usually found in bodies of water (lakes, oceans and rivers) as well as domestic tap water, swimming pools, hot tubs, soil and air.
Many different species of acanthamoeba exist. Acanthamoeba organisms do not generally cause harm to humans (we come into contact with them when we wash, swim, drink water etc), but they can cause a serious eye disease if they infect the cornea. Not all species of acanthamoeba have been found to cause corneal infections. AK is most common in people who wear contact lenses, but anyone with a corneal injury is susceptible to developing the infection.
Acanthamoeba has a life cycle of two stages: an active form (when the organism feeds and replicates), and a dormant form (when the acanthamoeba protects itself from attack by developing into a cyst).
In the early stages of the disease, the cornea can become irregular due to the infection and inflammation, which can affect your vision.
You may also have light sensitivity (also termed photophobia), which is a symptom of the inflammation and infection in your cornea.
Tears are a natural reaction to disruption of the corneal surface and are a reflex response to the infection.
AK can be extremely painful, although not all patients experience intense pain
Around 85% of cases of AK have been associated with contact lens wear.
There are a number of different factors which are known to increase the risk of contracting AK. The biggest risk factor is exposure to water (generally through swimming or showering in contact lenses, rinsing or storing lenses in water and handling lenses with unwashed or wet hands). Improper contact lens hygiene, including not disinfecting lenses properly and not cleaning and changing contact lens cases regularly have also been shown to increase the risk of infection. Those who do not wear contact lenses may still contract AK, although it has a much rarer incidence than in contact lens wear.
Due to the way that UK domestic water is stored and supplied, incidence of the disease is generally higher in the UK than in other parts of the world. Studies suggest that AK affects around 2 in 100,000 contact lens wearers per year in the UK, which is around 20 times less than the number of daily wear soft contact lens wearers with bacterial infections. Since 2011, Moorfields Eye Hospital and other centres in the UK and USA have reported a three-fold increase in the number of cases of disease, although it still remains rare.
Acanthamoeba keratitis (AK) can be extremely painful, although not all patients experience intense pain. The cornea is one of the most sensitive organs, with the highest density of pain receptors in the body. This means that any injury to the cornea can be very painful. Pain can also be triggered by the body’s immune response to the infection in your cornea - this is called an inflammatory response and may be one of the reasons your eye is red as well as painful. The medicines used to treat AK can be quite harsh and, in some cases, can also irritate the surface of your cornea. Your doctor will try to strike a balance between effective treatment of the infection and preventing further irritation on the corneal surface.
Light sensitivity (also termed photophobia) is a symptom of the inflammation and infection in your cornea because the cornea, which is usually clear, turns cloudy and scatters the light around. You may also have light sensitivity because you have been given an eye drop that temporarily widens the pupil, the hole through which light enters the eye. Sometimes the iris (the coloured part of the eye) can go into spasm when the cornea is infected, which can also cause pain, so these drops may help relieve the pain but may also make you more light sensitive. Tears are a natural reaction to disruption of the corneal surface and are a reflex response to the infection. They act to remove irritants from the surface of the eye.
In the early stages of the disease, the cornea can become irregular due to the infection and inflammation, which can affect your vision. This can occur quite suddenly, and you should inform your ophthalmologist as soon as possible if this happens to you. As the infection responds to treatment, patients can notice their vision improve as the inflammation reduces and the surface heals. In later stages of the disease, scarring on the front of the cornea, resulting from long-term inflammation, is usually the reason for vision loss. In some patients, scarring can be quite extensive and may need further therapy (e.g. a cornea transplant) to rehabilitate vision once the infection is over. A degree of permanent vision loss occurs in around a quarter of cases.
At Moorfields Eye Hospital, we have only seen cases of bilateral AK (affecting both eyes) where the patient has been infected in both eyes at the same time rather than it spreading from one eye to the other.
Acanthamoeba is an opportunistic organism in that it is widespread in the environment, but fortunately only rarely invades human tissue to cause disease. It’s extremely unlikely for acanthamoeba to spread from person to person. There are some extremely rare strains of acanthamoeba that can affect the brain; most of these cases occur in immunocompromised patients and are not related to contact lens wear. However, it’s still a good idea to take sensible precautions to ensure that other bacteria or germs do not spread between your eyes or from your nose/mouth to your eyes. Always wash your hands and dry them thoroughly before and after putting in your eye drops. Also make sure that you don’t touch your eye with the dropper or bottle top when applying eye drops.
Around 25% of cases of AK seen at Moorfields result in a corneal transplant. There are different types of transplant – and these carry different risks. Some are carried out to improve your vision at the end of infection. Other transplants are carried out, on actively inflamed eyes, as part of therapy.
The therapeutic transplants are usually for corneal perforations, although the success rate of these is poorer than the transplants to improve vision, therefore the procedure is rarely used unless absolutely necessary.
There is also a risk of a recurrence of AK post-surgery and this is one reason why corneal transplants are generally delayed until the eye has been infection free for some time. Your doctor will discuss what’s right for you and separate information will be provided if you are a possible candidate for a corneal transplant.
For patients who have poor vision but do not require a transplant, vision can be improved using a rigid contact lens. Your ophthalmologist will discuss all options with you at the appropriate time.
In order to provide you with the best care, we need to re-review your situation, especially any changes since your last appointment, as it may have an effect on your current treatment.
The UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) suggest all contact lens-wearing patients report their case of acanthamoeba keratitis via their Yellow Card reporting scheme. It is important for people to report problems experienced with medical devices as these are used to identify issues which might not have been previously known about. The MHRA will review the product if necessary and take action to minimise risk and maximise benefit to the patients. You can do this at yellowcard.mhra.gov.uk. Other countries have similar reporting schemes, so please check with your doctor for details.
You may find some other information about AK on the internet, but please bear in mind that much of this information may be inaccurate or out of date. Instead, please share this leaflet, (which is regularly reviewed and updated) with friends/family and others, to help them understand AK better.
There are also a number of social media forums where AK patients from all over the world talk and provide support to each other. Talk to your doctor if you require more detailed information about your specific case to give to your employer.
There are regular informal meet ups for acanthamoeba keratitis (AK) patients and their friends and families in London, which are also live streamed online for those who do not live nearby. We try and arrange this meeting once a year outside of working hours, and often have expert speakers and group discussions on how to raise awareness of AK, or how to participate in research.
There are several promising new drugs being developed, but it is likely to be years before they are used on patients.
There are a number of studies currently being undertaken by centres including Moorfields Eye Hospital and the UCL Biomedical Research Centre (BRC) to better diagnose, treat and prevent acanthamoeba keratitis. A clinical trial is also currently underway to develop the first properly licensed treatment for the infection.
Living with Acanthamoeba Keratitis. Acanthamoeba Keratitis (AK) is a rare condition that occurs when microscopic amoeba invade the cornea – the clear layer - at the front of the eye.
The amoeba normally live in water and soil and, although the infection has many causes, there is a known risk of infection that can occur when contact lenses come into contact with water because the contact lens can transfer the amoeba to the cornea.
Around 85% of Acanthamoeba Keratitis cases in the UK occur in contact lens wearers.
We want everyone to enjoy the freedom that contact lenses offer and give you some basic but vital steps to follow to keep your eyes healthy. Sairia, one of our patients, lost a year of her university course and badly damaged her sight due to poor contact lens care.
“I got the Acanthamoeba when I first started uni. So, I started in September and then I was officially diagnosed in like October. So, it was really hard for me to be living in London on my own. I was in halls and I didn't know like two people in halls, so it was just an awkward time, especially when my vision started to go.
“Being on the streets of London with loads of people walking everywhere, I got quite self-conscious about where I was walking. I felt like I couldn't see at that time. Whereas now I'm kind of used to it, but I felt like over there I couldn't see at all. So, I was knocking people in the street, it just knocked my confidence a bit I think and it made me not want to go out. Especially the light, I'd wake up some mornings and my eye would just be really bad and I’d just not want to even open my eyes, let alone like out of bed. I spent most of my day asleep, I barely went into uni.
“And then I got admitted into hospital in the easter, and then just stopped going to uni so I missed the whole summer term. And then I think that really put me back, not in terms of like doing work at uni but socially. It's only now that I'm really integrating with people there because I was just spending so much time back in Southend, and at hospital appointments. I missed so much, and I couldn't go out at all in the evenings or anything, so I didn't really – socially - meet a lot of people, especially when I was wearing the eyepatch! I just didn't want to see anyone.
“[I was] sitting on the bus on my own wearing an eyepatch and a child looks up in his mum and said “is she like a pirate mummy?” I didn't want it wear it, but it was just so much more comfortable when I put it on. So, yeah, I kind of got over the fact that it was embarrassing.
“My grandma basically thought it was conjunctivitis, so she just gave me like a general like medicine for conjunctivitis. I took it home, did it overnight and then when I woke up, in the morning, it made me feel a lot worse about my eye. I felt like there was a proper problem then, whereas before I thought ‘it must be just like a small infection or something’. And I was just a bit worried because this is my eye.
“So, she took me to another doctor who looked at my eye and said ‘Oh. I think it’s an ulcer, or something.’ So, he thought it was an ulcer, and then he took me to another doctor, who was an eye doctor I think, and he said ‘I think you've got this thing called Acanthamoeba, I can't be sure, but you have to go to hospital today.’ I was like ‘oh my god I've got to go to hospital!’
“They started putting me or all these drops every hour, they'd wake me up and put the eyedrops in for about two days, and then I could do that on my own. Then for the first week or so I went back to the doctor every few days, and then it was like every week or so. Then got less and less until, eventually, I was referred to Moorfields.
“I was up and down last year, so my eye would be stable for like a few months and then it would go bad again, so the symptoms would come up. Then I'd notice that my vision would get worse again.
“I've usually been in every month, and this is the first time they said to come back in three months, so it's going very well. Basically I'm right at the end of treatment and within the next couple of weeks I'll completely come off the drops. So they'll be the first time in the last two years”
“Have you had problems with depth perception?”
“Oh yeah! A lot of the time I'll pour a drink and it's just a lot further away from where the drink is, and I just poured orange juice all over the table. Obviously if I'm crossing a road and I need to look in that direction there's no vision over there, so I can’t just glance over and look. I have to turn my head fully. Sometimes I just don't and it's quite bad, but if I'm trying to get somewhere… I guess I've had times where I get beeped to get out of the way.
“But my eye’s been stable throughout this whole school year, so this year has been really fine. I've noticed such a big difference in how I've got to know people a lot easier this year, and integrated a lot better. The difference is really quite a lot.”
The impact of acanthamoeba keratitis on those affected can be extremely difficult. Some patients feel they need additional emotional support, in particular with adjusting to fluctuating vision and changes in appearance as a result of the infection.
Moorfields Eye Hospital provides a dedicated patient support and counselling service and can provide information, advice and counselling at the time of diagnosis, throughout your treatment and during your follow-up. You can contact the team by calling 020 7566 2385 or by emailing moorfields.referralscounselling@nhs.net .You may be prompted to leave a voicemail but please be assured that this line is confidential. It is helpful to keep the message short and clear, including your contact details. You can also contact the corneal nursing team on 020 7566 2405.
Eye clinic liaison officers (ECLOs) are available at Moorfields Eye Hospital in City Road to assist those living with sight loss. This includes patients, their relatives and carers. For more information about ECLO services at City Road, please ask a member of staff for the information leaflet, which is also available at the health hub, located at the main entrance of the hospital.
You can self-fund or use private medical insurance to fund your treatment.