Nearly one million clinic visits are made yearly for keratitis, with contact lens wear being the single biggest risk factor.¹ Specific issues include overnight lens wear and inadequate replacement, cleaning and disinfection of contact lenses and lens cases. While these have been prevalent for decades, regulatory bodies only elected to devote added attention to disinfection standards and the approval process for contact lens care products following microbial keratitis outbreaks in 2006 and 2007.

International Accord
On Sept. 23, 2014, the International Organization for Standardization (ISO) published the latest version of its contact lens solution disinfection testing guidelines. ISO standards are typically developed by committees comprised of globally recognized experts in the field. 

ISO 18259:2014 includes recommendations for lens soaking and storage periods when contaminating microorganisms are introduced through patient handling. To develop these recommendations, the antimicrobial efficacy of the test solution was evaluated at specific time intervals of 24 hours, seven days and the maximum labeled storage as stated by the lens case manufacturer. Five challenge organisms were tested: Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcesens, Candida albicans and Fusarium solani.²

A separate set of lens case wells was prepared for each time period, and three wells were evaluated for each test condition.³ Lenses from group one (i.e., low water nonionic hydrogels), group four (i.e., high water ionic hydrogels) and group five (i.e., high oxygen permeability silicone hydrogels) were used.  

Your Move, FDA
The FDA (with assistance from the CDC) is working to update its contact lens and lens accessory guidelines. At meetings held last year, input was sought on a number of proposals: (1) a new grouping system for silicone hydrogel (SiHy) lenses, (2) a new method to assess the interactions between lens materials and multipurpose cleaning solutions, (3) whether current microbiological tests should be modified to include “real world” test parameters and (4) the impact of tap water in RGP lens care.⁴

The proposed system divides SiHy lenses into five subgroups based on water content, ionicity and hydrophobicity, with recomendations that the solution compatibility of each subgroup be tested individually.⁵ Interestingly, these parameters can be used to predict preservative uptake for both conventional and SiHy lenses; thus, the FDA proposes using it to screen lenses for preservative uptake effects that may compromise disinfection.^5,6 

With respect to microbiological testing, the FDA will add Acanthamoeba to the list of challenge organisms evaluated by the ISO. Though the recommendation was made before, consensus methodology was not yet developed and test parameters varied widely between laboratories.⁴ The FDA will also add two new strains of Pseudomonas and update methods for testing soil and tracking known organisms.

The FDA also plans to reevaluate and clarify GP lens disinfection guidelines as further data becomes available. GP lens solutions cleared by the FDA before 2008 recommend rinsing lenses with water prior to chemical disinfection to break up debris and remove deposits, despite the fact that GP lens exposure to contaminated water has been linked to Acanthamoeba keratitis.^5,7

Overall, the new FDA contact lens disinfection guidelines are expected to take the ISO 18259 standard a step further with greater consideration paid towards new organisms, uncommon lenses and “real-world” factors such as lens cases and storage times, while also allowing for adaptability as new information, lenses and pathogens come to light.   

1. CDC. Estimated Burden of Keratitis—United States, 2010. Morbidity and Morality Weekly Report. November 2014;63(45):1027-1030.
2. EVS. Ophthalmic optics — Contact lens care products — Method to assess contact lens care products with contact lenses in a lens case, challenged with bacterial and fungal organisms (preview). Available at: www.evs.ee/preview/iso-18259-2014-en.pdf. Accessed January 26, 2015.
3. Rosenthal RA, Sutton SV, Schlech BA. Review of standard for evaluating the effectiveness of contact lens disinfectants. PDA J Pharm Sci Technol. 2002 Jan-Feb;56(1):37-50.
4. U.S. FDA. Ophthalmic Devices Panel Meeting [online transcript]. November 14, 2014. 
5. U.S. FDA. Ophthalmic Devices Panel Meeting [online transcript]. May 13, 2014. 
6. Green JA, Phillips KS, Hitchins VM, et al. Material properties that predict preservative uptake for silicone hydrogel contact lenses. Eye Contact Lens. November 2012;38(6):350-7.
7. Legarreta JE, Nau AC, Dhaliwal DK. Acanthamoeba keratitis associated with tap water use during contact lens cleaning: manufacturer guidelines need to change. Eye Contact Lens. March 2013;39(2):158-61.