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• Observations on data analysis on acanthamoeba keratitis
  Ankur Barua, Sunil Shah
  Published on: 14 October 2018

• Published on: 14 October 2018

  Observations on data analysis on acanthamoeba keratitis

  • Ankur Barua, Consultant Ophthalmologist University Hospitals Coventry and Warwickshire
  • Other Contributors:
    • Sunil Shah, Consultant Ophthalmologist

  Dear Editor
  We read the above paper with much interest and welcome the review and analysis of trends in acanthamoeba keratitis – a very important complication from contact lens wear. The paper discusses the incidence of acanthamoeba keratitis at Moorfields Eye Hospital, a large tertiary referral centre.
  We note an incidence of 18.5 cases per annum in 1997-1999, rising to a mean of 50.3 per annum in 2011-2016 and hence has been quite rightly quoted as almost a 3 fold increase in cases.
  We would however suggest some caution when using those figures to state that there is an epidemic at present.
  When one attempts to take into account the fluctuations in numbers of contact lens wearers with the United Kingdom per year and relate that to incidence of acanthamoeba keratitis one has a slightly modified view.1 There has been a steady increase in contact lens wear with figures from the ACLM estimating 4.2 million CL wearers in 2016. A figure has been created showing this relative incidence in a chart format.2
  The figure represents the number of cases diagnosed at Moorfields divided by the number of contact lens users (rising from 1.6 million in 1992 to 4.2 million in 2016). Therefore the mean number of cases when adjusted for CL wearers is 8.5 per year with a standard deviation of 5.8, with 11.8 in 2015 and 14 in 2016.
  Whilst there is still a significant rise in cases, compared to the mainly stable period of 1996-2010, the rates are still lower t...

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  Dear Editor
  We read the above paper with much interest and welcome the review and analysis of trends in acanthamoeba keratitis – a very important complication from contact lens wear. The paper discusses the incidence of acanthamoeba keratitis at Moorfields Eye Hospital, a large tertiary referral centre.
  We note an incidence of 18.5 cases per annum in 1997-1999, rising to a mean of 50.3 per annum in 2011-2016 and hence has been quite rightly quoted as almost a 3 fold increase in cases.
  We would however suggest some caution when using those figures to state that there is an epidemic at present.
  When one attempts to take into account the fluctuations in numbers of contact lens wearers with the United Kingdom per year and relate that to incidence of acanthamoeba keratitis one has a slightly modified view.1 There has been a steady increase in contact lens wear with figures from the ACLM estimating 4.2 million CL wearers in 2016. A figure has been created showing this relative incidence in a chart format.2
  The figure represents the number of cases diagnosed at Moorfields divided by the number of contact lens users (rising from 1.6 million in 1992 to 4.2 million in 2016). Therefore the mean number of cases when adjusted for CL wearers is 8.5 per year with a standard deviation of 5.8, with 11.8 in 2015 and 14 in 2016.
  Whilst there is still a significant rise in cases, compared to the mainly stable period of 1996-2010, the rates are still lower than those experienced in 1993-4 once numbers of wearers is taken into account.
  In addition, one should consider other causes for increased numbers of cases diagnosed.
  Firstly one should acknowledge the increased awareness by optometrists and ophthalmologists as to the possibility of acanthamoeba keratitis and improvements in the early diagnosis.
  There are also possible changes in referral patterns to Moorfields Eye Hospital from other hospitals (i.e. a high index of suspicion may lead to early transfer of suspected cases). This is certainly what we have seen in the Midlands.
  The results from treatment can also be relatively good with prompt modern treatment. In a recent review of 13 confirmed cases at UHCW, Coventry over the last 12 months, none of the patients required surgical intervention and all recovered vision (with over 85% complete improvement in acuity). 45% of patients were correctly diagnosed with acanthamoeba keratitis on the first eye casualty visit and treatment was dual topical therapy.
  Whilst we applaud the sentiment in this paper and the recommendations made, perhaps one needs to consider that is what was seen in one location, all be it a very large hospital – the hospitals of the 2 senior authors have seen more than 20 cases in the last year alone and hence the presentation of about 50 cases per annum cannot be easily extrapolated without taking into account a number of other factors.
  1The Association for Contact Lens Manufacturers. www.aclm.org.uk. Technical summary. Contact lens year book 2016.
  2Separate figure comparing CL wearers to acanthamoeba numbers from figures given by Carnt et al.

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  Conflict of Interest:
  None declared.

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