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Acanthamoeba keratitis in 194 patients: risk factors for bad outcomes and severe inflammatory complications
  1. Nicole Carnt1,2,3,
  2. Dana Robaei3,4,
  3. Darwin C Minassian5,
  4. John K G Dart3,6
  1. 1 School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia
  2. 2 Centre for Vision Research, The Westmead Institute for Medical Research, Westmead, New South Wales, Australia
  3. 3 Moorfields Eye Hospital NHS Foundation Trust, London, UK
  4. 4 University of Sydney, Sydney, New South Wales, Australia
  5. 5 EpiVision Ophthalmic Epidemiology Consultants, London, UK
  6. 6 National Institute of Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
  1. Correspondence to Dr Nicole Carnt, School of Optometry and Vision Science, The University of New South Wales, Sydney, NSW 2052, Australia; n.carnt{at}


Background/aims To determine demographic and clinical features of patients with Acanthamoeba keratitis (AK) that are independent risk factors both for bad outcomes and for severe inflammatory complications (SIC).

Methods A retrospective audit of medical records of AK cases at Moorfields Eye Hospital from July 2000 to April 2012, including 12 earlier surgical cases. Cases with a bad outcome were defined as those having one or more of the following: corneal perforation, keratoplasty, other surgery (except biopsy), duration of antiamoebic therapy (AAT) ≥10.5 months (the 75th percentile of the whole cohort) and final visual acuity ≤20/80. SICs were defined as having scleritis and/or a stromal ring infiltrate. Multivariable analysis was used to identify independent risk factors for both bad outcomes and SICs.

Results Records of 194 eyes (194 patients) were included, having bad outcomes in 93 (48%). Bad outcomes were associated with the presence of SIC, aged >34 years, corticosteroids used before giving AAT and symptom duration >37 days before AAT. The development of SIC was independently associated with aged >34 years, corticosteroids used before giving AAT and herpes simplex virus (HSV) keratitis treatment before AAT.

Conclusions The prompt diagnosis of AK, avoidance of a misdiagnosis of HSV keratitis and corticosteroid use before the exclusion of AK as a potential cause of keratitis are essential to the provision of a good outcome for patients and for the avoidance of SIC. Older age is an unmodifiable risk factor that may reflect differences in the immune response to AK in this patient subset.

  • cornea
  • epidemiology
  • contact lens
  • infection
  • inflammation

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  • Contributors DCM and JKGD conceived the study and designed the analysis. NC and DR collected the data, DCM analysed the data and all authors interpreted the data and contributed to the drafts and final manuscript.

  • Funding From anonymous donors to JKGD’s undesignated research funds, through a Grant from Moorfields Eye Hospital Special Trustees Reference MEC 1307A. The research and part of JKGD’s salary were supported by the National Institute for Health Research (NIHR) Biomedical Research Centre, based at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology. NC was supported by an NHMRC Early Career CJ Martin Fellowship (APP1036728) for this work and is now supported by a University of NSW Scientia Fellowship. DR is supported by an NHMRC Early Careers fellowship (APP1073846).

  • Disclaimer The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.

  • Competing interests None declared.

  • Patient consent This was a retrospective audit of medical notes, and waiver for consent was approved by the institutional data management board.

  • Ethics approval The Moorfields Eye Hospital Clinical Research Management and Audit Department approved the study.

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

  • Data sharing statement This is the fourth of a series of publications on this cohort of patients with Acanthamoeba keratitis, and no additional data are available.

  • Presented at This manuscript was presented as a poster at Association for Research in Vision and Ophthalmology, Baltimore, 2017.

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