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Study outlines method to determine efficacy of contact lens solutions
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A recent study has designed a reproducible and quantifiable method for assessing the disinfecting abilities of several commercially available contact lens care solutions specifically for Acanthamoeba.
Acanthamoeba trophozoites and cysts were grown in an axenic broth from a reference strand of A. castellanii, the study authors said. These organisms were then exposed to five contact lens disinfectant solutions. After 6 hours of contact, the log reductions in trophozoite visibility ranged from 3.8 in one solution to 0.1 in another.
At timed intervals samples were removed and dilutions made across the wells of a 96-place microtitre plate. The presence or absence of amoebal growth in the wells at each dilution was measured, and the number of remaining trophozoites or cysts computed.
“Acanthamoeba trophozoite and cyst disinfectant efficacy testing is a skilled technique,” Simon Kilvington, PhD, told Primary Care Optometry News. “This study represented many years of research designed to create a reproducible method for performing efficacy testing against Acanthamoeba trophozoites and cysts.”
Dr. Kilvington noted that, as a rule, trophozoites are typically more susceptible and easier to eradicate than cysts.
The experiments, sponsored by Abbott Medical Optics, were conducted in triplicate and repeated between three to eight times in 2 years, with comparable results.
Ninety percent of cases of Acanthamoeba occur in contact lens wearers, with an incidence of about two to 20 cases per million lens wearers, Dr. Kilvington said.
“Acanthamoeba keratitis remains a serious ocular infection associated with contact lens wear,” Dr. Kilvington said. “There is a need to develop contact lens care solutions with efficacy against this organism, and this requires a standardized assay method with inter- and intra-laboratory reproducibility.
“Acanthamoeba can adhere tenaciously to contact lenses (notably silicone hydrogel types) and are not removed by rinsing or soaking alone,” he added.
For more information:
- Simon Kilvington, PhD, is associate director of microbiology for Abbott Medical Optics Inc. He can be reached at AMO, (714) 247-8254; Simon.Kilvington@amo.abbott.com.
Reference:
- Kilvington S, Lam A, Lonnen J. Development of a standardised method for the quantitative determination of contact lens disinfectant efficacy against Acanthamoeba. Paper presented at: ARVO; May 3, 2010; Ft. Lauderdale.