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Written on 12th September 2023 by Sita Soni

The British Contact Lens Association estimates that around 3.7 million people, or 9% of the adult population, wear contact lenses in the UK. Contact lenses provide an effective, convenient and visually appealing method of eyesight correction but can also increase the wearer’s risk of eye infection. Most minor eye irritations and infections are quickly diagnosed and respond effectively to treatment, with no ongoing harm to the patient. However, we are pursuing claims for increasing numbers of people who have been left with permanent loss of vision as a result of delays in diagnosis and treatment of a rare cause of eye infection, known as acanthamoeba. 

What is Acanthamoeba Keratitis (AK)?

Acanthamoeba keratitis (AK) is a parasitic infection of the cornea, the curved, transparent, outer ‘window’ which covers the front of the eye. AK infection is caused by a microscopic organism (amoeba) which are found in nature, in the soil or in the water of lakes, oceans and rivers. Acanthamoeba organisms are also found in household tap water, hot tubs and swimming pools, and can be circulated in the air by heaters and air-conditioning units.  They are usually harmless to humans, but can cause loss of vision or blindness if they infect the cornea of the eye and are left untreated.

Who is at risk of Acanthamoeba Keratitis?

Acanthamoeba keratitis (AK) most commonly affects people who wear contact lenses. In fact, 85% of all AK infections are associated with wearing contact lenses.

Contact lens wearers have increased risks of eye infection from various causes, including bacterial, viral (e.g. herpes simplex virus or HSV), fungal or acanthamoeba. The Royal College of Ophthalmologists has encouraged efforts to raise public awareness about the infection risks associated with wearing cosmetic contact lenses and urged clinicians to consider the possibility of acanthamoeba infection whenever a cosmetic contact lens wearer presents with corneal inflammation, before assuming the infection is viral.

The AK risk for contact lens wearers is increased by exposure to water, such as swimming or showering whilst wearing their lenses, rinsing or storing their lenses in water, or handling their lenses with unwashed or wet hands, or by poor hygiene in the disinfecting and cleaning of lenses or contact lens cases. The risk of AK is higher in the UK than abroad, owing to the way that our household water is supplied and stored. 

Trauma or injury to the cornea increases the risk of developing AK infection, particularly where associated with water or nature, such as whilst skiing or gardening.

People who don’t wear contact lenses can also develop acanthamoeba keratitis but it is much more common in contact lens wearers. Very rarely, acanthamoeba infection can affect the brain, usually in people with compromised immune systems. Acanthamoeba does not spread from person to person.

Diagnosis and treatment of Acanthamoeba Keratitis

Acanthamoeba keratitis (AK) is not straightforward to diagnose. In its early stages, AK has similar signs and symptoms to other microbial corneal infections, which makes it harder to identify the cause of the infection.

AK can be extremely painful and the inflammation and infection can cause irregularities in the cornea which cause sudden loss of vision, but with timely treatment the inflammation should reduce allowing the cornea to heal and the vision to improve. If treatment is delayed and the disease is allowed to progress, the front of the cornea becomes scarred from long-term inflammation, causing permanent loss of vision. Other symptoms of AK may include light sensitivity (photophobia) caused by inflammation and infection of the cornea, or the eye may water in response to the irritation.

The main difference between AK and other types of microbial eye infections is that it does not respond to inappropriate treatments, such as antibiotics which only treat bacterial infection.  As AK cannot be reliably diagnosed from the patient’s symptoms and signs, diagnostic tests should be carried out. These include checking for signs of inflammation in the cornea, a corneal scrape (to analyse cells from the surface of the cornea) or swab (to check for acanthamoeba DNA), or scanning with a confocal microscope to check for acanthamoeba cysts in the layers of the cornea.

Treatment for acanthamoeba keratitis usually involves regular use of anti-amoebic antiseptic drops. Anti-inflammatory or painkilling medication may also be needed. In around 10% (1 in 10) cases of AK, the patient may also need antibiotics to prevent or treat additional bacterial infection.

Claims for loss of vision from delayed diagnosis or treatment of acanthamoeba keratitis

Acanthamoeba is one of the rarer causes of eye infection but when it occurs it is critical that treatment takes place quickly to prevent permanent loss of vision in the affected eye. Clinicians are expected to consider acanthamoeba as a possible (differential) diagnosis whenever they are faced with a patient who has signs of eye infection, particularly where their risk is greatly increased from the use of contact lenses.

Failing to consider and investigate acanthamoeba as a cause of keratitis, if necessary by referring the patient to an eye specialist or hospital with facilities for confocal microscopy, may be negligent even at an early stage when other possible causes of infection are still being investigated and have not been ruled out. This is because the effective ‘treatment window’ time for acanthamoeba can be as short as 6 to 8 weeks, before the patient suffers irreparable and permanent loss of vision, but there is no harm in treating the patient for suspected acanthamoeba infection whilst also testing for viral, bacterial or fungal causes for the infection.

We have noticed some common themes in acanthamoeba blindness claims for our clients, which suggest that the risks to contact lens wearers and the importance of prioritising treatment for a differential diagnosis of acanthamoeba are not fully understood. Cases may be (unsuccessfully) defended on the basis that there was no positive diagnosis of acanthamoeba to justify or mandate starting treatment, or that bacterial or viral causes for the patient’s infection had not yet been ruled out. Waiting for a positive diagnosis of acanthamoeba before starting treatment causes unwarranted delay which greatly increases the risk of permanent loss of vision to the patient. Confirmed diagnosis of acanthamoeba is not necessary before starting treatment, and is often only reached too late, when antibiotic, anti-viral and other treatments have proved ineffective and rule those conditions out.

In some cases, a persistent assumption that there must be a viral cause (such as HSV) blinds the clinicians to the importance of safeguarding the patient’s vision from other potential causes, which would be obvious on a review of the ‘bigger picture’ or a referral to a corneal specialist. When treatment for acanthamoeba is finally started, we see instances where a different clinician then sees the patient and prematurely stops the anti-acanthamoeba treatment having decided that investigations or treatment should assume a more likely diagnosis.

Another common factor in delayed AK treatment cases is the negligent use of steroid medication to reduce inflammation. In most acanthamoeba keratitis cases, steroids provide false reassurance by reducing the inflammation, masking the true cause of the infection, and are known to make the patient’s outcome and prognosis far worse. Steroid treatment can also increase the risk of additional complications, including cataract and glaucoma (raised pressure within the eye). Where steroids are needed, their use must be very carefully managed.

The message from these cases is that acanthamoeba should be treatable with timely treatment based on an awareness of the patient’s risks, but that delays in treatment cause irreparable injury to the eye and permanent loss of vision.

Compensation for loss of vision caused by acanthamoeba negligence

Compensation in acanthamoeba negligence claims must take into account the full impact of the loss of vision on the patient. Physically, the patient may lose all their vision in the affected eye and be left with pain which in some cases is severe enough to lead to removal of the eye. Severe AK may also cause complications, such as cataract and glaucoma, and increased risks of total blindness, depending on the long-term health of the other eye. Ongoing treatment or surgery may be needed, such as corneal transplantation or removal of the eye. 

Psychologically, the patient may need counselling and specialist support to come to terms with their new partial-blindness disability, altered appearance and anxiety or vulnerability.

Practical and financial support may be needed to address and compensate for the affected person’s loss of independence and reduced ability to work, drive or get out and about, pursue household tasks, hobbies and sports safely.

If you have suffered severe injury as a result of medical negligence or have been contacted by HSIB/HSSIB/MNSI/CQC or NHS Resolution, you can talk to a solicitor, free and confidentially, for advice about how to respond or make a claim by contacting us.