What could be easier than blinking your way to clearer, more comfortable vision? In-eye cleaning/wetting drops have been on the market for several years, yet when I talk to many practitioners, I find confusion and resistance to such products. This hesitation is understandable. Over the past few years we’ve had a barrage of marketing that upsets our time-honored dogma: Don’t sleep in your contact lenses. Rubbing maintains clean lenses. And, of course: Never put surfactant cleaners in your eyes. So while continuous-wear lenses and “no-rub” solutions have been getting all the glory, in-eye cleaning products have quietly made their way into our practices.
How Do They Work?
The biggest confusion is in how these products work. They are designed to remove loosely adhered lens contaminants, including protein, lipid and calcium deposits. These products target two mechanisms of action, namely surfactant cleaning and surface wetting.
Surfactant cleaners traditionally have been harsh chemicals that are incompatible with corneal tissue and designed to reduce surface tension and aid in removing proteins, lipids, minerals, cellular debris and microorganisms. Surfactants (short for “surface active ingredients”) work by means of hydrophobic hydrophilic interactions promoting micelle formations and by lowering surface tension. In-eye cleaning products use gentle, surface tension-reducing or weakly ionic surfactants to interact with the lysozomes. The resulting emulsified debris is then whisked away with the blink.
Wetting agents are key to long-term comfort with such in-eye products. Beyond surface wetting, they prevent attachment of debris to the lens surface. Alcon’s Clerz Plus wetting agent, Tetronic 1304, is attracted to the hydrophobic areas on the lens surface, thereby promoting a hydrophilic coating and preventing protein binding (this claim is FDA-approved). Tetronic 1304 can remain on the lens up to 24 hours.
Tromethamine, Complete Blink-N-Clean’s buffer agent, helps prevent further protein deposition by occupying protein-binding sites. This product’s proven wetting agent, hydroxypropyl methylcellulose (HPMC), lowers surface tension by increasing viscosity of the solution. It helps balance “wettability” with cleaning action to provide harmony between lens and eye surface needs. In addition, HPMC may help buffer the preservative, PHMB, in BlinkN-Clean, minimizing toxic effects.
All Lenses Benefit
In-eye cleaners are appropriate for all lens types, since wearers of soft lenses, silicone hydrogel lenses and RGPs all experience deposition and drying. Deposition of the lens surface begins within minutes of lens application to the eye, and it increases over time. Some patients remain symptom-free, while others experience increasing dryness and irritation. Certain populations of patients may benefit from these products more than others. For example, silicone hydrogel wearers rarely have the benefit of a rub, rinse or soak cycle. Women experiencing hormone changes may have exacerbated dryness and deposition in any contact lens. RGP wearers who use “one-bottle” solutions may mistakenly equate it to its soft-lens, one bottle, “no-rub” counterpart.
Educate Your Patients
Some patients think that no-rub solutions are the same as wetting drops. “It’s all the same stuff anyway,” one patient told me, explaining that both products went by the same trade name. In one head-to-head study involving an in-eye cleaning product and a commonly-used rewetting drop, patients preferred the in-eye cleaner for improved end-ofday comfort and reduced dryness.
It is the job of the eyecare physician to dispel the myth that all solutions and lens care regimes are created equal. New products with improved efficacy give us a perfect opportunity to discuss and remedy our patients’ bad habits. Discussing product benefits like this one will enhance the doctor/patient relationship.
Of course, efficacy may vary depending on lens type, wearing habits, tear chemistry and quality, and exogenous factors such as environment and climate. In my practice, I use these in-eye products judiciously. I never hand a patient a sample without explaining why I have selected that product. I also document which products and any specific instructions I have given the patient in his or her chart. Prudent use of these products can increase long-term comfort-and possibly thwart patient drop-out.
So when our patients “no rub,” maybe they’ll also blink!
Dr. Sindt is Director of Contact Lens Service at the University of Iowa Hospitals and Clinics, Iowa City, Ia.
Contributor: Christine W. Sindt