contact lens care and compliance
In Defense of Water: Another Look at Lenses and Water
BY MICHAEL A. WARD, MMSC, FAAO
Water is everywhere. We are water. Our bodies are approximately 60 percent water. Our brains are 70 percent water. Our lungs are 90 percent water. Water is the universal solvent: we use it to clean our environments. Water is used to clean and prepare our food and drinks for ingestion. In the event of chemical spill, we are instructed to rinse our face and eyes with water. We bathe in it. We wash our hands in it. We cannot live without it. But, to quote W. C. Fields, "I never drink water because of the disgusting things that fish do in it." Not all water is equal.
Reports of Acanthamoeba keratitis in recent years have focused our attention on the use of water as an accoutrement to contact lens wear. How do we explain that bacterial contamination has been reported in up to 80 percent of contact lens storage cases among asymptomatic lens wearers, yet the incidence of microbial keratitis is relatively low except for sporadic outbreaks involving specific products?
In May 2007, the Centers for Disease Control and Prevention reported increased incidence of Acanthamoeba keratitis among contact lens wearers: 85 percent were soft lens wearers, 7 percent were GP lens wearers, and 9 percent did not wear contact lenses.
The question of water quality due to lowered concentrations of chlorine was raised by Joslin and Tu (2006) in their report of Acanthamoeba keratitis in the Chicago area. Most clinicians agree that patients should not use water to rinse soft contact lenses and should not wear contact lenses during water activities. Acanthamoeba cysts also live in air, dust, and soil.
Water and GP Lenses
What are our practices and recommendations regarding water use with rigid lenses? Should we use tap water to rinse lens cleaner from GP lenses prior to lens disinfection?
In a 1990 paper, Shovlin raised the specter of Acanthamoeba keratitis associated with tap water and rigid lens use and recommended that tap water not be used following lens disinfection. This still seems reasonable. Lens cleaners must be thoroughly rinsed from lens surfaces to avoid irritation from residual surfactants, abrasives, or solvents left on the lens or transferred to the lens storage case. Salines and multipurpose solutions (MPSs) are unlikely to be as effective as water at removing surfactants. In addition, when rinsing lens cleaners with salines or MPSs, the tendency is to use less product for economy, which may result in inadequate rinsing.
Davis (1996) compared lens case contamination at three and six months of tap water use versus saline use for rinsing of GP lenses (crossover) and found a slightly higher contamination with saline, although not significantly different in frequency of case contamination between the two methods; no case was found to have fungi or amoeba.
Keep It Clean
It is important for us to remember that contact lens wear is not a sterile event; however, it should be a clean event. Ideally we wash our hands with soap and water prior to handling our contact lenses. If we rinsed the soap off of our hands with water, we "contaminated" our hands with water. It is likely that a few microbes still exist on our hands, but it is unlikely that they will cause a problem. The key is to prevent a large number of organisms (inoculum) from overwhelming our bodies' defense mechanisms and causing an infection. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #162.
Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and Director, Emory Contact Lens Service. He is also a consultant to B&L and has participated as an advisory panel member for AMO.