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Acanthamoeba keratitis: confirmation of the UK outbreak and a prospective case-control study identifying contributing risk factors
  1. Nicole Carnt PhD1,2,3,
  2. Jeremy J Hoffman MBBS3,
  3. Seema Verma3,
  4. Scott Hau3,
  5. Cherry F Radford PhD3,
  6. Darwin C Minassian4,
  7. John K G Dart3,5
  1. 1 School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
  2. 2 Centre for Vision Research, Westmead Institute for Medical Research, Westmead, Australia
  3. 3 Corneal and External Disease Service, Moorfields Eye Hospital NHS Foundation Trust, London, UK
  4. 4 EpiVision Ophthalmic Epidemiology Consultants, Penn, UK
  5. 5 National Institute of Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
  1. Correspondence to Professor John K G Dart, Moorfields Eye Hospital, London EC1V 2PD, UK; J.Dart{at}


Background/aims Acanthamoeba keratitis (AK) is a chronic debilitating corneal infection principally affecting contact lens (CL) users. Studies were designed to test claims that the UK incidence may have increased in 2012–2014 and to evaluate potential causes.

Methods Annualised incidence data were collected from January 1984 to December 2016. Case-control study subjects were recruited between 14 April 2011 and 05 June 2017. Reusable CL users with AK were recruited retrospectively and prospectively. Controls were reusable CL users, recruited prospectively, with any disorder other than AK. Multivariable analysis of questionnaire data measured independent risk factors for AK.

Results The current outbreak of AK started in 2010–2011 with an incidence threefold higher than in 2004–2009. Risk factors for AK were: Oxipol disinfection, CLs made of group IV CL materials, poor CL hygiene, deficient hand hygiene, use of CLs while swimming or bathing, being white British, and for those in social classes 4–9.

Conclusion AK is a largely preventable disease. The current outbreak is unlikely to be due to any one of the identified risk factors in isolation. Improving CL and hand hygiene, avoiding CLs contamination with water and use of effective CL disinfection solutions, or daily disposable CLs, will reduce the incidence of AK. In the longer-term, water avoidance publicity for CL users can be expected to reduce the incidence further. Ongoing surveillance of AK numbers will identify changes in incidence earlier. Evaluation of Acanthamoeba contamination in end-user drinking water would contribute to our understanding of regional variations in the risk of exposure.

  • contact lens
  • epidemiology
  • infection
  • Acanthamoeba keratitis

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  • Contributorship NC: submitted the research and ethics applications, recruited the cases, co-ordinated recruitment of the first set of controls, prepared the incidence dataset from 2000 to 2014 and contributed to the planning and execution of all aspects of the study. JJH: collected the incidence data for 2015/2016. SV: facilitated the identification of controls and cases in the Moorfields A&E Deptartment. CFR: assisted questionnaire design, the dataset collection and recruited the second set of controls. DCM: contributed to study planning and carried out the statistical analysis. JKGD: planned the study, assisted with the data collection and co-ordinated the preparation of the manuscript. All authors contributed to the manuscript.

  • Funding Grants from Fight for Sight (1542/43 and 1465/6), Moorfields Eye Hospital Special Trustees (ST 12 09A), anonymous donors to Moorfields Eye Charities, and from CooperVision UK. Part of John Dart’s salary was paid by the National Institute of Research (NIHR) Biomedical Research Centre (BRC) at Moorfields Eye Hospital NIHR BRC. Dr Carnt was supported by an NHMRC Early Career CJ Martin Fellowship (APP1036728).

  • Disclaimer None of the funders had a role in the design or conduct of this research although one reviewed the manuscript; modifications were limited to clarification and grammatical changes. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.

  • Competing interest statement CooperVision UK, one of whose products has been identified by this study as a risk factor contributing to the development of Acanthamoeba keratitis, funded the recruitment of the second set of controls. This was to verify the findings of the first set as there was a perception that the selection of these may have been biased. This did not prove to be the case and the company has since phased out the product. CooperVision did not influence the study design. Representatives of CooperVision reviewed the manuscript but made no changes other than clarifications and grammatical changes.

  • Patient consent Not required.

  • Ethics approval National Research Ethics Service Committee London-Hampstead, REC Reference 13/LO/0032 and the Moorfields Eye Hospital Research Governance Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement None are available. The study database, from which the reported analysis has been done, can be provided if this is requested by a commercial organisation who wishes to contest the findings. We believe we have precluded any real likelihood of such a request being made by having had extensive pre-submission discussions with CooperVision, whose product is identified as being associated with an increased risk of AK. They have agreed the contents of the manuscript.

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