Enzymes? Why Would We Use Enzymes?
BY 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 Lens Service.