Contact Lens Care & Compliance
Hydrogen Peroxide Contact Lens Disinfection, Part 1
By Susan J. Gromacki, OD, MS, FAAO
I last wrote in this column on hydrogen peroxide contact lens disinfection more than five years ago (December 2006 and February 2007 issues). Since then there has been a resurgence in its utilization, from 6.4 percent to 15.8 percent of the United States market (Nielsen, 2006 and 2011). With so many more practitioners now prescribing peroxide for their patients, the time is right to review the topic again.
Mechanism of Action
Three-percent hydrogen peroxide (H2O2) is an efficacious microbial disinfectant (Shoff, 2008; Johnston, 2009; Hughes, 2001). It is active against bacteria, fungi (including spores and yeasts), viruses, and protozoa. Few patients affected during the contact lens-related Fusarium and Acanthamoeba keratitis outbreaks used a hydrogen peroxide-based disinfection system (Chang, 2006; Verani, 2009).
Its mechanism of action is initiated by penetrating a hydrogel contact lens material and expanding its matrix. It oxidizes microbes, creating the free radical superoxide, which is toxic to DNA; this provides a thorough cleaning of the lens. Because of its hypotonic nature and pH of 4.00, it is also able to break protein and lipid bonds—affecting microbial cell structures—and remove trapped debris. Unlike many multipurpose soft contact lens care solutions, it can penetrate microbial biofilms. It works quickly, taking about 10 minutes of exposure to eliminate most bacteria and 45 to 60 minutes for fungi. In addition, its active ingredient/disinfectant is hydrogen peroxide itself, rather than preservative—making it a good system for hypersensitive patients or those who have dry eye.
H2O2 also demonstrates biocompatibility; in three recent studies, patients utilizing hydrogen peroxide had the lowest incidence of corneal infiltrative events (Chalmers, 2011; Carnt, 2009) and solution-induced corneal staining (Carnt, 2009; Andrasko, 2012).
Because H2O2 can be toxic to the epithelium, you must educate patients about the importance of full neutralization of the peroxide. This takes less than six hours and can be achieved only with the (basket-like) case and the catalytic enzyme tablet or platinum catalytic disc enclosed with the given system. What remains after neutralization is unpreserved saline, in which microbial growth can occur. Although most systems are approved for up to seven days of lens storage in an unopened case, it is safest to repeat the disinfection/neutralization process every day or two.
Instruct patients to replace their cases and discs at least every three months, since older discs may not completely neutralize the H2O2. Although typical residual amounts measure between 1ppm to 15ppm (Rosenthal, 1988; Lowe, 1992), research has shown that levels below 300ppm have minimal effect on the corneal epithelium (Millard, 2011). With that said, hydrogen peroxide straight from the bottle should never be used to rewet the eye or to rinse contact lenses due to its potential to cause hyperemia, tearing, epiphora, chemosis, burning, stinging, photophobia, and/or superficial punctate keratitis. A patient's emotional response to these events often outweighs his ocular one, and with frequent application of artificial tears, the keratitis usually heals within a day. As a warning to patients, all major ophthalmic hydrogen peroxide manufacturers utilize a red-colored dropper tip on the bottle. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #198.
|Dr. Gromacki is a diplomate in the American Academy of Optometry's Section on Cornea, Contact Lenses and Refractive Technologies and practices in Lutherville, Md.|