Contact Lens Care & Compliance
MPS Dual Disinfection Trends
By Michael A. Ward, MMSC, FAAO
Since June 2010, the contact lens solution industry has introduced three new-generation multi-purpose solutions for soft lenses. Each has enhanced antimicrobial efficacy and meets the FDA criteria as a stand-alone multipurpose disinfecting solution (MPDS). These products are often touted as “dual disinfection” products because they each contain two significant chemical disinfectants. In fact, dual disinfection is not new to the industry.
Heat was the original FDA-approved disinfecting method. A move away from heat and into cold chemical lens hygiene in the 1970s and 1980s produced products employing dual disinfection.
Early products contained chlorhexidine and thimerosal as active ingredients. Hypersensitivity to thimerosal, along with toxicity reactions attributed to chlorhexidine, resulted in these chemicals being largely removed from the soft lens market.
Generations of MPS improvements have occurred since then, which brings us to our current generation of products.
Alcon's Opti-Free PureMoist is the most recent entry into the enhanced MPDS, dual disinfection arena, following Biotrue (Bausch + Lomb [B+L]) and RevitaLens Ocutec (Abbott Medical Optics [AMO]). Opti-Free Pure-Moist uses the same powerful dual disinfection formulation of polyquaternium-1 (PQ-1) with myristamidopropyl dimethylamine (Aldox) as its predecessor, Opti-Free Replenish, except that the concentration of Aldox is increased from 0.0005% to 0.0006%. Biotrue combines PQ-1 with the very strong antimicrobial polyhexamethylene biguanide (PHMB). RevitaLens OcuTec combines PQ-1 with alexidine dihydrochloride, a broad-spectrum biocide that is commonly used in mouthwashes. These combinations of preservatives provide strong, broad-spectrum antimicrobial coverage. See Table 1 for a comparison of ingredients.
The paired preservatives alone do not make the product. The chemical combinations of buffers, chelants, surfactants, electrolytes, and lubricants work together to produce the final contact lens care products' efficacy and comfort. 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 email@example.com.