Would We Use Enzymes?
MICHAEL A. WARD, MMSC, FAAO
When was the last time you prescribed enzyme
cleaning to enhance the efficacy of your patient's contact lens care? Do you recommend
enzymes for soft lenses (HEMA or silicone hydrogel), GP lenses
or both? Are enzymes necessary now that we have disposable soft lenses and multipurpose
care products? The answer? It depends.
A Common Regimen
We routinely prescribed enzyme cleaning as part of a lens care
regimen when patients kept soft lenses for a year or two and rigid lenses until
they were lost or broken. We learned that lenses become increasingly covered with
deposits that can initiate ocular inflammations, primarily superior palpebral giant
papillary conjunctivitis, more recently called contact lens papillary conjunctivitis
(CLPC). Daily cleaners and proteolytic enzymes can moderate the incidence of CLPC.
Three chemical proteolytic enzymes were formulated for contact
lenses: papain (from papaya), pancreatin (from pork proteases) and subtilisin (endopeptidase
isolated from Bacillus subtilis). Each is safe for all lens materials.
Changes in Lenses and Care
As disposable lenses replaced more durable lens modalities, lens
care regimens yielded to one-bottle multipurpose (MPS) products, followed by the
no-rub era of MPS labeling. Although MPS products don't contain enzymes, other chemicals
are added to inhibit protein deposition.
As lens care disposability increased, lens care decreased. Two-week
disposable lenses now account for approximately 65 percent of the soft lens market.
The shorter lens life logically negated the need for enzyme treatment. However,
less than half of patients prescribed two-week replacement schedules replace them
in two weeks; statistics are similar for monthly replacements.
More Cleaning Required
Enter silicone hydrogel lens materials. Silicone hydrogel lenses
have answered the gas exchange problem for soft lenses and at the same time presented
us with new challenges. Silicone hydrogel lenses react differently with tear proteins
and lipids. They attract higher lipid deposition and lower protein deposition, but
the degree of protein denaturation is higher (higher denaturation is associated
with greater propensity for CLPC).
Silicone hydrogel materials must be cleaned; ignore the 'no-rub'
labeling. Reinstitute the 'rub and rinse' instructions. Chemically, silicone hydrogel
lens surfaces are prone to environmental contamination such as from hand creams
and make-up. Consider adding a separate solvent-type daily cleaner (Lens Plus Daily
Cleaner [AMO], Pliagel [Alcon], Miraflow [CIBA Vision]) if necessary. Avoid using
abrasive cleaners on silicone hydrogel materials. Weekly enzymes may also be helpful
in preventing or controlling incipient CLPC. However, the best lens choice for a
patient who has a history of CLPC is daily disposables.
When to Use Enzymes
All HEMA based (durable) lenses kept for three months or more
should undergo weekly enzymatic treatment. Enzymes generally are not indicated for
disposable lenses kept for one month or less. An exception is a patient who has
a history of GPC/CLPC and desires silicone hydrogel monthly replacement lenses.
Here I recommend a weekly enzymatic treatment (Ultrazyme [AMO] or Unizyme [CIBA])
with hydrogen peroxide disinfection.
GP lens wearers prone to deposit formations often benefit from
weekly use of the Boston One Step Liquid Enzymatic Cleaner (B&L) or daily use
of Supraclens (Alcon).
Mr. Ward is an instructor
in ophthalmology at Emory University School of Medicine and Director, Emory Contact
Contact Lens Spectrum, Issue: September 2005