Acanthamoeba keratitis
- D V Seal1,
- T K Beattie2,
- A Tomlinson2,
- D Fan3,
- E Wong3
- 1Applied Vision Research Centre, City University, Northampton Square, London EC1V 0HB, UK
- 2Department of Vision Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, UK
- 3Departments of Ophthalmology and Centre for Clinical Trials and Epidemiological Research (School of Public Health), Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong
- Correspondence to: David Seal; 100756.3112{at}compuserve.com
We read with interest the report by Radford et al on the incidence of acanthamoeba keratitis and the suggested relation with hardness of water.1 However, we disagree with their findings and believe their study is flawed for two reasons.
Firstly, the incidence of acanthamoeba keratitis has been underestimated by approximately 33% since their monthly questionnaire reporting system yielded an average return of only 67%. A high non-response rate over 30% is considered unreliable for making inferences for the whole population.2 Furthermore, the authors estimated the “incidence” rate using the “complete” cases, which is a biased sample. Even then, if the non-response rates were below 30% in this study, the authors did not provide the precision of the “incident” rate and attempt to apply a statistical weighting approach to remove or reduce non-response bias.
Of 179 positive reports collected, only 106 (59%) met their case definition criteria. This further reduced their number of cases but will have contributed to their diagnostic accuracy. A further five …
