Management of Acanthamoeba keratitis
12 December 2014
UCL research has identified epidemics of Acanthamoeba infection amongst UK contact lens wearers, established the epidemiology of the infection, introduced improved approaches to contact lens hygiene, developed the most sensitive test to make a diagnosis, and discovered a new treatment for established infection.
Acanthamoeba keratitis (AK) is a rare corneal infectious disease caused by the pathogenic free-living protozoan Acanthamoeba spp. Incidence of the infection is low (1 in 100,000 in the EU), but has life-changing consequences, due to the prolonged and painful infection, with half the patients requiring more than six months' treatment, and severe loss of vision or blindness in 25%. In countries where contact lenses are commonly worn, lens use accounts for over 85% of cases. AK also occurs after corneal trauma, particularly in rural environments. AK is on the rise in developing economies and there is no approved drug to treat this disease.
I started using PHMB drops and the pain in my eye quickly reduced. I used the drops for four months as a precaution. I have had no further pain or infection and my sight has been saved. - Jennifer, Moorfields patient
Through the systematic study of AK at the UCL Institute of Ophthalmology, including laboratory, epidemiological and clinical research, researchers have identified avoidable risk factors, developed better techniques for diagnosis, and introduced and developed a novel class of topical disinfectants (the biguanides). Overall, UCL work has improved the prevention, diagnosis and treatment of AK. Guidelines for the prevention of AK now incorporate UCL findings. For example, the US Centers for Disease Control and Prevention (CDC) Healthy Contact Lens Wear and Care website references this work, and the British Contact Lens Association's public site uses UCL work on risk factors in relation to swimming, extended-wear contact lenses, and hygiene related to contact lens cases. UCL have also worked to raise practitioner and public awareness of the risks for AK - for example UCL research was featured in a 2011 article, Contact Lens Problems on patient.co.uk, and in a 2013 case study article in The Optician. In 2014, Moorfields Eye Hospital ran a campaign on contact lens care using UCL studies that was publicised in the Mail on Sunday and in the Optician.
I feel fortunate that I was seen at Moorfields Eye hospital within a few days of my symptoms becoming distressing and painful, and that I began to recover quickly. - Bryony, Moorfields patient
UCL work on risk factors for AK has been incorporated into contact lens packaging. Furthermore, the research led to a new disposable contact lens case being supplied with each bottle of contact lens solution sold. It has also stimulated further work to develop new and improved cleaning solutions and cases, and has been cited in many patents for such products. UCL research demonstrating that chlorine-based solutions are not effective against AK has led to this type of solution being removed from the market - for example Softab in 1995. In 2007, a similar occurrence of an outbreak of AK infection was identified in the USA using UCL methods, and was associated with the use of Complete Moisture Plus. This solution was withdrawn. UCL research is used by manufacturers in the development of more appropriate solutions, for example, Menicon cited UCL research in their evaluation of the efficacy of a new multipurpose solution, MeniCare Soft, against Acanthamoeba. UCL research has demonstrated that diagnosis and treatment within three weeks of onset improves outcomes. UCL were the first to investigate the value of the identification of Acanthamoeba DNA by Polymerase Chain Reaction (PCR) as the most sensitive and specific method for the diagnosis of AK, since confirmed by several other independent studies. PCR for diagnosis of AK is becoming widely used in routine diagnostic laboratories.
At the same time that UCL recognised the epidemic of cases in the UK there was little really effective treatment apart from the use of a diamidine, to which many cases were resistant. The result was that patients needed therapeutic corneal transplant surgery with poor outcomes and high morbidity. In response to this UCL collaborated with a protozoologist (Dr Simon Kilvington, University of Leicester) who suggested the use of the biguanide Polyhexamethyl biguanide (PHMB) also known as Polyhexanide. Biguanides (PHMB and chlorhexidine) with or without a diamidine (propamidine or hexamidine) have become the standard of care for this condition around the world.