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Issues surrounding contact lens product testing go beyond scope of recent workshop
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The September workshop hosted by the U.S. Food and Drug Administration Center for Devices and Radiological Health, the American Academy of Optometry, the American Academy of Ophthalmology, the American Optometric Association and the Contact Lens Association of Ophthalmologists discussed a number of ideas that need to be thoroughly tested before implementation into standards for product testing.
Since the incidents involving two contact lens solutions in 2006 and 2007, experts in the U.S. and around the world have done considerable work to assure that product testing results in a safe and effective experience for the contact lens wearer. It is important that this work by not only FDA but the American National Standards Institute (ANSI) and International Organization for Standardization (ISO) be a part of the basis for improving our approach to the development of new products.
It is important to note that the FDA Ophthalmic Devices Panel, in their deliberations in May, strongly recommended that the FDA work closely with the standards-setting organizations, ANSI Z-80 and ISO TC172/SC7.
All research not reflected in workshop
The September workshop only addressed four restricted, narrow areas of the testing protocols and failed to take into account the body of work carried out by industry, government and academic and practicing medical professionals as part of the ongoing process in ANSI and ISO. The initial discussions on this area started after the recalls of 2006 and 2007 and progressed through an FDA workshop in early 2009, as well as ongoing meetings of ANSI Z-80 and ISO TC172/SC7/WG9. The progress made in those meetings was not reflected in the narrow scope of the discussion at the September workshop.
The primary discussion centered on the current standard for disinfection based on ISO 14729. Since 2007, the work in this area has led to new approaches that have been or are currently being developed as global standards in which the U.S. (including representatives of the FDA) have participated in the development. The first is ISO 18259, issued in October, which adds the contact lens and the lens case to the testing matrix, and further adds organic soil to the mix.
While the addition of Acanthamoeba to the testing approach for products is certainly a laudable goal, there are many questions to be answered for these protozoa. The initial approach recommended by a consensus of the 2009 FDA workshop was to evaluate the encystment of Acanthamoeba during exposure to disinfection. The reason for this approach was based on research by Simon Kilvington, PhD, which demonstrated that conversion to the cyst form was a distinguishing feature of the product associated with the outbreak in 2007.
Currently, a draft ISO standard, DIS 10945, is in the balloting stage; it specifies the methodology for measuring the conversion of trophozoites to cysts by exposure to a disinfecting solution. None of this approach was a part of the agenda for the 2014 workshop.
Further, the testing of disinfection efficacy, that is, kill potential of Acanthamoeba, is still under discussion. There are a number of methods available to grow these organisms as the trophozoite form as well as conversion to the cyst form, and data has been published by a number of researchers in this area. These various methods are being assessed and tested, but the work is arduous and requires multilaboratory evaluations. The selection of the right species and the right representative strain has long been a source of discussion among experts, as have the methods and conditions to grow this organism. The focus today is on a single species and strain with parallel evaluation of a second species and strain also as a potential candidate.
In the ISO 14729 document, while organic soil is not required in the standalone portion, it is an alternative and has been used by products seeking labeling for elimination of the rub step. In addition, the secondary or regimen test, a simulated-use test, may use organic soil as part of the protocol. The September workshop discussed changing from the current composition using heat-deactivated yeast cells and serum to a composition of tear components. A definitive direction was not agreed on by the participants. The recently issued ISO standard (ISO 18259) includes organic soil.
Selecting organisms
The selection of the current panel of organisms used in ISO 14729 for disinfection testing was carefully vetted to represent organisms believed to be important in the disinfection process. Those who have read the standard find that the inclusion of viruses was considered, as had been the practice before the current international standard. The argument was that, given the mechanism of inoculation, finding viruses would indicate that the patient was already infected. Transmission of viruses between patients was considered and is addressed by a separate testing protocol for the use of lenses by multiple patients, such as trial lenses.
As for Acanthamoeba, the rationale for not including it was also discussed based on the data available. It is interesting to note that this standard was reviewed and re-issued in 2012, without significant comment from any U.S. participants, including the FDA, as to including additional organisms or changing the use or composition of organic soil.
Additional testing protocols are being addressed and are at various stages of U.S. and international review. The workshop had none of these approaches as a part of the agenda for the meeting or questions to be addressed.
The recently approved ISO 18259 also uses the current panel of organisms.
Selection of strains
I was interested in the comments about selections of strains used for disinfection efficacy testing. The current standards outline the maintenance of cultures based on the recommendation of the American Type Culture Collection. It is important that strains are a part of a recognized culture collection to assure that they do not change over time. The cultures are carefully documented and are maintained for a set number of passages (five) from the culture collection material. Changes for a strain in the collection require it to be withdrawn from the collection.
Scientific studies of individual products have examined the susceptibility of various strains from organisms with little variability. It was mentioned at the workshop that virulence of an organism is not necessarily correlated with resistance of the organism to disinfection with disinfecting agents. Antimicrobial agents used for disinfection are primarily designed to work at the cell surface and cell membrane and are not subject to the changes noted in the antibiotic resistance.