contact lens care
Another Solution Recall: Is This the End of No Rub?
BY MICHAEL A. WARD, MMSC, FAAO
On May 25, 2007 Advanced Medical Optics (AMO) voluntarily recalled its Complete MoisturePlus (CMP) multipurpose contact lens solution. AMO said it was "acting with an abundance of caution" in removing CMP from the market. This action followed reports and data from the U.S. Centers for Disease Control and Prevention (CDC) regarding an increase in Acanthamoeba keratitis (AK) among lens wearers.
Data Show An Emerging Trend
The data originated from a CDC survey of 22 ophthalmology centers across the country whose purpose was to assess the incidence of AK. Data from 13 centers demonstrated an increase of AK starting in 2004 and continuing to the present. These data indicate a statistically significant increase in AK associated with the use of CMP.
According to the CDC, the historical incidence of AK in the United States is approximately one to two per million contact lens wearers. As of March 2007, 138 cases of culture positive AK had been recorded since January 2005. The CDC performed an initial analysis after interviewing 46 patients: 39 (85 percent) wore soft lenses, three (7 percent) wore rigid lenses and four (9 percent) reported no lens wear; 35 (83 percent) reported showering while wearing lenses and 16 (38 percent) wore lenses while swimming. A significant 56 percent reported using primarily CMP.
This recall of CMP follows last year's recall of ReNu with MoistureLoc (Bausch & Lomb), which was associated with an increased incidence of Fusarium keratitis. Is it purely a coincidence that two major MPS products are associated with eye infections thought to be rare? Are we missing something here?
Various explanations have been postulated as to why we may be witnessing an increase in infectious keratitis. Data by Joslin and Tu et al (2006) suggest an epidemiological association between the lowering of chlorine levels in our water supply by the Environmental Protection Agency and an increased risk of AK. In 2003, the EPA decided not to monitor or regulate Acanthamoeba in public water supplies. The FDA doesn't require contact lens care products to kill amoebas.
Acanthamoeba feed on bacteria and fungi. Myself and other authors theorize that the lack of proper lens care and hygiene plays a significant role in contact lens-associated infections. It's well documented that the ‘rub and rinse’ step significantly decreases microbial contamination of lens surfaces. The dangerous complacency suggested by the "No Rub" label likely plays a role in the increased incidence of lens-associated infectious keratitis.
Are Reformulations to Blame?
Could recent reformulations of soft lens MPS products have diminished their antimicrobial efficacy? Beginning in 2004, the major MPS products were reformulated to address a loss of lens wearers due to perceived dryness symptoms. The latest formulations addressed dryness symptoms by dramatically increasing the cushioning/humectant/lubricating properties of the MPS products. We know that evaporative drying by certain MPS products can form films that protect growing microbes. Does increasing the lubricant concentrations of these products compromise antimicrobial efficacy?
It's important to realize that lens care is more market-driven and less practitioner-driven, so convenience and ease of use will continue to be important aspects of lens care. Nevertheless, proper patient education and monitoring can decidedly ameliorate weaknesses in lens care products. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #140.
|AK: Other Factors at Play|
|While the University of Illinois at Chicago study found that Complete MoisturePlus had a strong association with Acanthamoeba keratitis, the study also found a statistically weak association between reusing solution, rubbing the lenses when cleaning them and showering with lenses on.|
Dr. Charlotte Joslin, assistant professor of ophthalmology and visual sciences at UIC and principal investigator in the study, noted that recent Environmental Protection Agency regulations that decrease the levels of disinfectant in the water supply may have led to an increase in the microbial load that contact lens solutions must kill in order to prevent disease.
The complete study appears online in the American Journal of Ophthalmology.
Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and Director, Emory Contact Lens Service.