Contact Lens Care & Compliance
FDA Forging New Guidance
BY SUSAN J. GROMACKI, OD, MS, FAAO
The first silicone hydrogel (SiHy) contact lenses were introduced almost 14 years ago. As subsequent SiHy lenses were launched, they too were placed by the International Organization for Standardization (ISO) into the four existing lens material categories based on water content and ionic charge. This action was adopted by the U.S. Food and Drug Administration (FDA).
Over time, it became evident how much these materials differed from previous generations of soft contact lens materials, and in 2009 the ISO established a new category for them, Group 5. Now, the FDA is recognizing how much SiHy lens materials differ from each other and has begun to study their material properties in an attempt to subclassify them even further.
A recent paper (Green et al, 2012) describes the analysis of the water content, effective pore size, and preservative uptake of both SiHy and traditional hydrogel soft contact lenses. The authors— members of the Center for Devices and Radiological Health within the FDA—found that the water content and ionic charge of the contact lens materials are highly correlated with the degree of hydrophilic preservative uptake. Although not reported in this paper, the authors propose that material hydrophobicity should also be evaluated regarding the uptake of relatively hydrophobic preservatives and tear components.
Working Toward New Guidance
The guidance for lens care systems, “Premarket Notification (510(k)) Guidance Document for Contact Lens Care Products,” addresses salines, cleaners, chemical disinfecting/multipurpose solutions, lubricating/rewetting drops, heat disinfection, contact lens cases, and contact lens accessories and was last updated in 1997. The document provides recommended test methods for care systems, including chemistry, microbiology, toxicology, shelflife, and clinical testing. Although contact lens care solutions and materials have come and gone, and two contact lens solution-related keratitis outbreaks (Fusarium and Acanthamoeba) occurred between six and eight years ago, the FDA has not updated its guidance document. However, as two recently published papers attest, it has been working toward that goal (Eydelman et al, 2012a, Eydelman et al, 2012b).
According to the papers, the FDA devised a research plan to:
• Evaluate and better understand the properties of SiHy contact lenses.
• Develop “real-world” scenario experiments with contact lenses and their care products.
• Conduct preservative depletion and efficacy studies.
• Develop Acanthamoeba test methods.
Currently, the microbial testing regimen for multipurpose solutions does not utilize lenses in cases. In fact, the Stand-Alone portion of the test evaluates efficacy utilizing neither a lens nor a case. Not only is this not real-world, but solution-lens combinations do matter. For example, as described above, certain materials uptake some solutions more readily, rendering the disinfectant levels less effective. When patients also “top off” (add new solution to what remains in the case), the combined solution demonstrates little disinfection efficacy.
Finally, testing against American-Type Culture Collection strains is required for product market approval by the FDA. The five microorganisms (Serratia marcescens, Pseudomonas aeruginosa, Staphylococcus aureus, Fusarium solani, and Candida albicans) represent a diverse microbial challenge—but the list does not include Acanthamoeba. The FDA is currently working on a test methodology for evaluating the efficacy of lens care products against Acanthamoeba. This includes the importance of growing amoebas under the appropriate conditions to ensure that the efficacy of a multipurpose solution is not overestimated. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #206.
Dr. Gromacki is a diplomate in the American Academy of Optometry’s Section on Cornea, Contact Lenses and Refractive Technologies and practices in Chevy Chase, Md.