SUSAN J. GROMACKI, OD, MS, FAAO
Interestingly, none of the patients afflicted
during the Fusarium keratitis outbreak reported a hydrogen peroxide-based
disinfection system. Let's review this modality and its characteristics.
peroxide provides excellent antimicrobial efficacy. It works by penetrating the
hydrogel material and provides a thorough cleaning by expanding the lens matrix
and oxidizing microbes. Because of its hypotonic nature and pH of 4.00, it's also
able to break protein and lipid bonds and remove trapped debris. It also can penetrate
microbial biofilms. Most multipurpose soft lens solutions don't share this characteristic,
which may have contributed to Fusaria survival.
Hydrogen peroxide is also preservative-free ideal for
patients who have hypersensitivities or dry eye. Two commercially available systems
also contain additional wetting agents.
When patients use a hydrogen peroxide system alone with a 10-second
rinse, it's an excellent choice for contact lenses prescribed for three months or
less. When combined with a daily cleaner, hydrogen peroxide should be a system of
choice for lenses prescribed to last for three months or more.
The first one-step hydrogen peroxide system, AOSept (CIBA Vision),
appeared in 1982. It immediately proved more convenient than heat disinfection.
However, hydrogen peroxide's share of the solutions market has declined from 20
percent in 1993 to less than 8 percent today. This is certainly due to the continuous
improvement of multipurpose chemical disinfection solutions.
It may also result from marketing. Few H2O2
disinfection systems are sampled anymore. There's also the created perception that
our patients can't comply with a rubbing step or a solution that has a red warning
nozzle. Therein lies the primary disadvantage of the system a chemical keratitis
for unlucky patients who accidentally place a drop of H2O2
in their eyes.
The truth is, peroxide patients are among the most compliant and
the most loyal to their prescribed solution, as we witnessed this year with the
temporarily suspended production of AOSept and Clear Care (CIBA Vision).
The 3% concentration found in these solutions provides optimal
lens disinfection. In most instances, it takes about 10 minutes of exposure to eliminate
most bacteria and 45 to 60 minutes for fungi. You need to instruct patients that
this solution is microfiltered and not interchangeable with the large brown bottles
at the pharmacy.
Because H2O2 can be toxic to the epithelium,
you also must educate your patients about the importance of full neutralization
of the peroxide. Emphasize to your patients that they can achieve this only with
the (basket-like) case enclosed with their system. What remains afterward is unpreserved
saline; patients should apply their lenses directly from the case. Re-rinsing with
H2O2 is contraindicated, but with sterile saline is acceptable.
The neutralization occurs via either a catalytic enzyme tablet
or a platinum catalytic disc, depending on the solution brand.
Most systems specify a six-hour neutralization time, although
newer discs neutralize much quicker than older ones. Manufacturers recommend replacing
the disc/case every three months.
Inadequate neutralization may result in hyperemia, tearing, epiphora,
chemosis, burning, stinging, photophobia and/or superficial punctate keratitis.
With palliative measures, the anterior surface usually heals within about 24 hours.
In my next column, I'll discuss the characteristics of the various
brands of hydrogen peroxide available today.
Dr. Gromacki is in group
practice in Burke, Virginia, and has served as a faculty member at the University
of Michigan Department of Ophthalmology and Visual Sciences.
Contact Lens Spectrum, Issue: December 2006