Acantamoeba keratitis: peak of cases in the UK

Pubblicato il

Friday, 23 November 2018

Argomento

Eye infections

Recorded a particularly high rate of new cases of infection among contact lens wearers

The use of contaminated contact lenses has led to a significant increase in cases of Acanthamoeba keratitis in the South East of England, with rates almost tripling in 2010-2011 compared to 2004-2009.
The data of this 'epidemic' were reported in a study published in the British Journal of Ophthalmology.
Annualised incidence data were collected from January 1984 to December 2016.
Patients for the case-control study were recruited between April 2011 and June 2017.
According to data collected by Moorfields, there was an average increase of 50.3 cases per year between 2011 and 2016 in the South East of England. Arguably, the figure should also be considered representative for the rest of the UK, as Moorfields treats more than 35% of all Acanthamoeba cases in the country.
According to the authors, researchers at the University of New South Wales in Sydney (Australia) and Moorfields Eye Hospital in London (England), this spike is probably due to a variety of factors, including changes in disinfectant products and materials used to produce contact lenses.
A first relevant factor is the increasing use in the UK of domestic water collected in tanks, in which conditions are favourable for the proliferation of microorganisms.
To obtain a more precise map of risk factors, the researchers compared habitual contact lens users, who had presented to the hospital with Acanthamoeba keratitis, with daily contact lens users, who had come to the hospital for other emergencies.
The results indicated as risk factors:
- Use of unsuitable cleaning solutions
- High water content hydrogel lenses (group IV)
- Poor contact lens hygiene
- Do not wash hands before handling lenses
- Wearing contact lenses in the swimming pool or bathtub
- White British ethnicity.
Disinfectant solutions that are not fully effective in cleaning contact lenses have already been among the causes of Acanthamoeba keratitis spikes in both the US and the UK in the past. In reality, there is no standard methodology for testing in vitro reproducible disinfectant solutions to be used against Acanthamoeba and independent tests have shown that multi-purpose disinfectants are not effective against this micro-organism.
The role of the materials from which lenses are made is very complex, as the researchers point out, and one must also consider that microorganisms adhere differently to different types of materials. Since most keratitis is bacterial in nature, the researchers also hypothesised that materials research, by aiming to reduce the risk of bacterial keratitis, may have indirectly increased the risk of Acanthamoeba keratitis.
Therefore, as far as group IV contact lenses are concerned, the same researchers suggest that, rather than switching to another material, it would be better to aim at optimising all hygienic precautions, both with regard to lens cleaning and handling, and to avoid wearing them when exposed to water (shower, swimming pool, etc.).
Finally, it would be desirable to minimise the use of cleaning solutions by using daily disposable lenses whenever possible.