Contact Lens Care & Compliance
GPs and Acanthamoeba
BY MICHAEL A. WARD, MMSC, FAAO
A new U.S. Centers for Disease Control and Prevention (CDC) article described and identified the clinical presentation and outcomes of Acanthamoeba keratitis (AK) among GP lens wearers and identified modifiable risk factors (Cope et al, 2016). It focused on two CDC multistate investigations of nationwide AK outbreaks in 2007 and 2011.
The risk of contact lens-associated microbial keratitis (MK) increases significantly with continuous wear and when wearing contact lenses during water activities (e.g., swimming and showering) (CDC, 1986; Stehr-Green, 1989; Dart et al, 1999). It is well recognized that water and soft contact lenses do not mix (Ward, 2014; Ward, 2016), yet the lack of data to date about GP lenses and water has led to speculation. This latest article provides the first case-controlled series providing relevant data. According to the article, about 91% of GP lens wearers reported using a water rinse, and one-third reported storing their lenses in water. The jury is still out regarding the relative risk of MK among GP wearers using water to rinse lenses prior to disinfection.
Risks for MK can be mitigated through education and proper patient instruction. AK is primarily associated with soft lens wear and water exposure; soft contact lenses should never be exposed to water (Ward, 2016). GP lens-associated MK is relatively rare. However, it remains prudent to advise patients to avoid water exposure. Reported cases of Acanthamoeba infection in GP contact lens wearers have been few, and those reported are primarily associated with overnight lens wear and orthokeratology (Cope et al, 2016).
Here is a partial list of the CDC’s talking points about AK among GP contact lens wearers (CDC, 2016).
Results of the study by Cope et al (2016) showed the most significant risk factors for AK in rigid contact lens wearers were storing lenses in tap water, wearing their lenses while sleeping, topping off contact lens solution in the case, and wearing lenses for orthokeratology.
Storing Lenses in Tap Water Rigid lens wearers who stored their lenses in tap water were 16 times more likely to have AK compared to those who did not.
Wearing Lenses While Sleeping Rigid lens wearers who wore their lenses while sleeping were eight times more likely to have AK compared to those who did not.
Topping Off Contact Lens Solution Rigid lens wearers who topped off their contact lens solution were 4.8 times more likely to have AK compared to those who did not.
Wearing Lenses for Orthokeratology Wearing lenses for orthokeratology was found to be a significant risk factor for AK.
In a separate article in May, Sauer et al (2016) looked at risk factors for contact lens-related MK for rigid and soft lens wearers. They reported on a prospective, multicenter, case-control study of 499 contact lens-related MK cases and 508 contact lens wearer controls.
According to the study, risk factors associated with the greatest increased odds of lens-related MK were using disinfecting solution for more than three months (odds ratio [OR] of 1⁄41.94); cosmetic lens wear and the use of multipurpose disinfection solution (OR of 1⁄41.37 for both categories), and overnight lens wear and soft lens use (OR of 1⁄41.24 for both) (Ward, 2016).They reported rigid lens wear as relatively safe: “Relative to the CL material, [GP] CL were found to be safe with a protective OR (1⁄40.34 [0.21–0.57], P, 0.0001),” (Sauer et al, 2016).
These articles are important additions to our understanding of incidence, risk, and prevention of contact lens-associated MK. CLS
For references, please visit www.clspectrum.com/references and click on document #247.
Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and director, Emory Contact Lens Service. You can reach him at email@example.com.