CONTACT LENS CARE & COMPLIANCE

WHAT A LONG WAY WE’VE COME IN CONTACT LENS CARE

MICHAEL A. WARD, MMSC

We are at year’s end, and I am I reflecting on the modern evolution of contact lenses and lens care. Although I was not around in the early PMMA days, I still have a small handful of older hard lens patients who just could not give up the superior optics and indestructibility of their PMMA lenses. The 1970s introduced both rigid GP materials (cellulose acetate butyrate, siloxanyl/methacrylate copolymers, silicone resins, and elastomers) and first-generation soft hydrogel lenses. Care of hard and GP lenses was simple and not much different from today: rub with daily surfactant cleaner, rinse, and place in disinfecting/storage solution (not water) overnight.

Evolution of Soft Lens Care

Heat Disinfection Soft contact lens care has evolved significantly. The first U.S. Food and Drug Administration (FDA)-cleared hydrogel soft contact lens launched in the early ’70s. The FDA required the use of thermal (moist heat) disinfection. Patients were instructed to place their lenses in a lens case filled with saline and then to place the case in an Aseptor that generated heat and steam. The saline was prepared by dissolving a salt tablet in distilled water.

Homemade saline was later associated with bacterial, fungal, and amoebic infections and fell into disfavor. Heat-disinfected contact lenses were also associated with a shorter lens life, more attached proteinaceous lens deposits, and giant papillary conjunctivitis. Weekly enzyme (e.g., papain, pancreatin) treatments were added to remove/reduce protein deposits on lenses.

Cold Disinfection Systems Preserved saline products and cold (chemical) disinfection systems were introduced in the late 1970s. Cold disinfection systems used multiple products: daily cleaners, preserved saline rinse, and chemical disinfection overnight followed by a morning saline rinse to remove the harsher chemical disinfectants prior to lens wear. Early generation chemical disinfecting systems used a combination of thimerosal and chlorhexidine that created a powerful disinfecting product, but became associated with hypersensitivity and toxicity reactions, respectively.

Hydrogen Peroxide Systems In the early 1980s, the first (two-part) hydrogen peroxide disinfection system using a platinum-coated plastic disc to neutralize the peroxide into water, oxygen, and carbon dioxide was introduced. Hydrogen peroxide disinfecting systems offer excellent antimicrobial efficacy without preservatives. Additional peroxide systems were developed using other neutralizing systems, such as dilution, thiosulfate, and catalase. Disc-neutralizing peroxide systems have prevailed in the market and have recently enjoyed a resurgence.

Multipurpose Solutions Chemical-based all-in-one multipurpose solutions (MPSs) were developed to simplify lens care by encompassing lens cleaning, disinfecting, and storage components in one bottle. We were in the era of no-rub solutions, allowing simplicity at the expense of surface cleaning; this was a bad idea. For industry, creating an MPS is a difficult balance of surfactants to clean the lens and preservatives/disinfectants to remove pathogens and yet be mild enough not to cause damage or irritation to the ocular surface.

Peroxides have regained some popularity following soft lens MPS-associated outbreaks of microbial keratitis from 2004 to 2006.

Our latest generation of multipurpose lens care products uses several disinfectants (e.g., polyhexamethylene biguanide [PHMB], polyquaternium-1 (PQ-1), and alexidine) and offers superior disinfection with low incidence of toxicity or hypersensitivity.

No Lens Care Probably the greatest evolution affecting the lens care market in this century has been the growth of single-use, daily disposable soft lenses, thus eliminating the need for lens care solutions.

Beyond Soft Lenses

The growing popularity of scleral GP lenses has refocused our need for powerful daily cleaners, sterile non-toxic rinsing solutions, scleral lens-designed peroxide disinfecting products, and occasional additional strong cleaners. Industry will meet these needs.

Yes, we have come a long way, and the future is exciting. CLS

Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and director, Emory Contact Lens Service. You can reach him at mward@emory.edu.