Increase in acanthamoeba keratitis may be associated with use of multipurpose contact lens solutionBMJ 2012; 344 doi: http://dx.doi.org/10.1136/bmj.e1246 (Published 21 February 2012) Cite this as: BMJ 2012;344:e1246
- Haneen Jasim, F2 ophthalmology1,
- Nat Knox-Cartwright, fellow in ophthalmology1,
- Stuart Cook, consultant ophthalmology1,
- Derek Tole, consultant1
Acanthamoeba, a ubiquitous amoeba associated with stagnant water, can cause a sight threatening keratitis that is difficult to treat.1 Contact lens users are at greater risk of developing atypical keratitis, particularly when lens hygiene is poor.2
We reviewed case notes to try to identify risk factors that could explain the increased incidence of acanthamoeba keratitis at this eye hospital (figure⇓).
Since 2007, 19 cases of acanthamoeba keratitis have been treated at the hospital, 18 in contact lens users. Nine of the contact lens users used Sauflon All In One Light multipurpose contact lens solution, which is also marketed as Specsavers Easyvision Multipurpose Solution and Vision Express Multi Purpose M Lite (all nine used Easyvision). Other risk factors for acanthamoeba keratitis—for example, washing lenses in tap water and showering or swimming wearing lenses—were identified in 11 patients.
The potential association between use of a specific multipurpose solution is important, given that most contact lens wearers in the UK use daily disposable lenses, which do not require daily cleaning. Additionally, a multipurpose solution was withdrawn from the market following outbreaks of acanthamoeba keratitis in America and Singapore.3 4 Various studies looking into this link show mixed outcomes, and little consensus exists on how acanthamoebal disinfection should be tested. One study showed that acanthamoeba cysts are resistant to disinfection by several multipurpose solutions.5
The preservative in the Sauflon multipurpose solution is polyhexamethylene biguanide (PHMB) at a concentration of 0.0001%—the same as in the withdrawn solution. However, other ingredients (such as buffering agents) may also affect anti-acanthamoebal activity.6
Standards for anti-acanthamoebal activity of contact lens solutions do not currently exist despite recent concerns. Further research is needed on the links between contact lens care products, quality of cleaning, and standardisation to prevent acanthamoeba keratitis.
Cite this as: BMJ 2012;344:e1246
Competing interests: None declared.