Risk factors for acanthamoeba keratitis in contact lens users: a case-control study.
OBJECTIVE
To investigate reasons for an increase in cases of Acanthamoeba keratitis related to contact lenses.


METHODS
Case-control study. Cases were contact lens related acanthamoeba keratitis patients treated between 1 September 1989 and 31 August 1992. Controls were lens users without lens related disease who presented as new patients to the casualty department from 1 March 1992 to 31 August 1992. All subjects completed a questionnaire detailing lens use and hygiene practices.


METHODS
Eye hospital.


METHODS
35 cases with acanthamoeba keratitis and 378 controls.


METHODS
Relative risks comparing different contact lens types, socioeconomic classification, age, sex, lens use, lens wearing experience, hygiene compliance, and hygiene systems.


RESULTS
The crude relative risk for developing acanthamoeba keratitis with the use of daily wear disposable lenses was 49.45 (95% confidence interval 6.53 to 2227; P < 0.001) compared with conventional soft lenses (the referent). Multivariable analysis showed that this increased risk could be largely attributed to lack of disinfection (relative risk 55.86 (10 to 302); P < 0.001) and use of chlorine based disinfection (14.63 (2.8 to 76); P = 0.001) compared with other chemical systems (the referent). None of the other outcome measures showed a significant association.


CONCLUSIONS
Both failure to disinfect daily wear soft contact lenses and the use of chlorine release lens disinfection systems, which have little protective effect against the organism, are major risk factors for acanthamoeba keratitis. These risks have been particularly common in disposable lens use. Over 80% of acanthamoeba keratitis could be avoided by the use of lens disinfection systems that are effective against the organism.
Radford
C F
CF
Moorfields Eye Hospital, London.
Bacon
A S
AS
Dart
J K
JK
Minassian
D C
DC
D015823:Acanthamoeba Keratitis / Q000209:etiology*; D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D003261:Contact Lenses / Q000009:adverse effects*; D003262:Contact Lenses, Extended-Wear / Q000009:adverse effects; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects; D004203:Disinfection; D005260:Female; D006801:Humans; D006920:Hygiene; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012307:Risk Factors