WELLNESS
Caring for contact lenses
More than 140 million Americans require some form of vision correction.
Of this
number, 24 million wear contact lenses. The U.S. contact lens market is
shared
by daily and extended wear types of soft and rigid lenses. Lens
disposability,
advanced bifocal designs and effective astigmatism correction have
produced an
increased interest in contact lens wear. Reports of microbial keratitis
have
produced an increased interest of proper lens care and risks associated
with
lens wear. The incidence of ulcerative keratitis varies from 41 per
100,000 for
daily wear soft contact lenses to 209 per 100,000 wearing population for
extended wear contact lenses. When compared with other life risks, one is
more
likely to have been the victim of a robbery or to suffer an IRS audit
than to
have a contact lens-related corneal infection.
History
Shortly after the introduction of the corneal hard contact lens, it
become
apparent that proteins, mucus and oils from the tears would coat the lens
surfaces. Initial hard contact lens care was expedient; they were stored
dry.
In the early 1970s when soft contact lenses were introduced, lens care
became
more sophisticated, time-consuming and expensive. Early soft lens care
utilized
consumer-prepared saline (salt tablets dissolved in distilled water) to
be used
in conjunction with thermal disinfection. Although the considerable risks
of
using homemade saline have been well illuminated, the U.S. Food and Drug
Administration (FDA) continues to allow their presence in the U.S.
market.
Bacterial corneal ulcers, predominantly Psuedomona sp, have been
associated
with the use of homemade saline. In addition, as reported in a study by
the
U.S. Centers for Disease Control and Prevention, 50 percent of
acanthamoebic
keratitis cases were among contact lens wearers who used home-prepared
saline.
Current recommendations
Hard and rigid gas permeable contact lens care requires the following
daily
care regimen:
*Surfactant cleaning and sterile saline rinse followed by overnight
storage in
a chemical disinfectant/conditioning solution.
*Lens storage cases should be rinsed and left open to air dry during the
day
and disinfected (scalded) in boiling water weekly.
Soft lens care is slightly more time consuming although the basic steps
are
similar. Following surfactant cleaning and sterile saline rinse, the lens
must
be disinfected by one of the following methods:
*Cold chemical
*Oxidation (hydrogen peroxide)
*Thermal disinfection
Regardless of the method of prescribed disinfection, the daily
surfactant
cleaning of all lenses remians a very important step. It is the cleaning
step
that debulks the lens, removing the organic load and preparing the lens
surfaces for disinfection. If weekly enzymatic treated is used, the lens
needs
to be surfactantly cleaned prior to enzymatic treament and following
enzymatic
treatment to remove residual enzyme left on the lens surfaces. The lenses
should then be disinfected prior to being worn the following day.
Michael A. Ward is the director of the Contact Lens Service of the Emory
Eye
Center. The publication of "Wellness" is coordinated through the Seretean
Center for Health Promotion.