We are writing with regards to your recent article on “The Dangers of Mixing Solutions” (January/February 2011, Review of Cornea & Contact Lenses). We commend your message of recommending an expert recommendation for contact lens solutions, and ongoing patient education regarding proper contact lens practices at every visit. However, you stated in the patient education section that, “combining these technologically advanced medical device materials with different contact lens solutions can adversely affect contact lens comfort and increase risks for adverse events, such as microbial keratitis.” There are no clinical studies in the literature, that we are aware of, that show such association with microbial keratitis.

The solution recalls mentioned in the article were not shown to be associated with any particular lens/solution combinations. The article includes the strong statement, “The preservatives used in solutions are employed to kill pathogens; however, if these biocidal agents interact with the lens material, it decreases the disinfection profile of the solution originally approved by the FDA—even though no lens was used for testing.” The FDA now requires additional data beyond the traditional stand alone testing referenced in the article; for example, additional information including testing of biocidal activity of the solution against Acanthamoeba trophozoites and cysts. Regimen testing involves subjecting a variety of hydrogel and silicone hydrogel (SH) lenses that have been deliberately inoculated with multiple species of microorganisms to the proposed lens care regimen and evaluating the treated lenses and associated lens care soaking solution for viable recovery at the end of the lens disinfection period. Testing at Bausch + Lomb Incorporated includes a variety of traditional and silicone hydrogel contact lenses from the current lens manufacturers. Additionally, other tests that evaluate the entire system (solution, lens, case) are performed. This testing is performed based on discussions with the FDA regarding their expectations for data they want to see in a submission package. Indeed, clinical testing includes hydrogel and silicone hydrogel lens types and regimen testing includes multiple lens types.

Regarding figures 1 and 2, the correct reference is the manuscript from Alcon Research by Ruth A. Rosenthal, M.S., and colleagues.¹ Regardless, the methodology used to obtain these data does not simulate real world conditions from a microbiological perspective. In reality, the worn lens is added to the solution, thus simultaneously introducing the lens and any associated microorganisms to the system. Lens colonization, which is more relevant, was not measured or reported in this particular study design. The sample size of this study was very small—typically three lenses—and the data for any other challenge organisms or lens types are not presented.

Finally, in the section entitled “Understand the Risks: Preservative Release,” it is stated that Solution Induced Corneal Staining (SICS) has been shown to increase the risk of corneal infiltrative events. It is worth noting that this has been refuted by Dr. Loretta Szczotka-Flynn, O.D., M.S., Ph.D., and colleagues who reported, “Corneal staining is common during continuous wear of SH lenses, but it is not associated with the development of a corneal infiltrative event (CIE).”² Similarly, Dr. Mark Willcox, Ph.D., and colleagues found no directional relation between corneal staining and comfort, nor causal relation between SICS and infiltrates.³ Rather, there is growing evidence that MPS not showing transient fluorescence are associated with infiltrative keratitis observations. Specifically, recent reports have shown a high incidence of infiltrative keratitis in patients using high concentration Polyquad preserved multipurpose solutions with silicone hydrogel and hydrogel lenses.^4-6
In summary, while we agree with your message of providing patients with an expert opinion on lens care products as well as ongoing patient education, the information you provided seems to require a more thorough assessment to confirm its accuracy and relevance.

- Joseph T. Barr, O.D., M.S.
Vice President, Clinical and Medical Affairs, Vision Care, Bausch & Lomb Incorporated

- Marjorie J. Rah, O.D., Ph.D.
Manager, Medical Affairs, Vision Care, Bausch & Lomb Incorporated

1. Rosenthal RA, Dassanayake NL, Schlitzer RL, et al. Biocide update in contact lenses and loss of fungicidal activity during storage of contact lenses. Eye Contact Lens. 2006 Dec;32(6):262-6.
2. Szczotka-Flynn L, Lass JH, Sethi A, et al. Risk factors for corneal infiltrative events during continuous wear of silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci. 2010 Nov;51(11):5421-30.
3. Willcox MD, Phillips B, Ozkan J, et al. Interactions of lens care with silicone hydrogel lenses and effect on comfort. Optom Vis Sci. 2010 Nov;87(11):839-46.
4. Kislan TP, Hom MM. Corneal infiltrates with multipurpose solutions and contact lens combinations. Invest Ophthalmol Vis Sci. 2010;51:E-Abstract 3424.
5. Kislan TP. Case Characteristics of Persons Presenting With Contact Lens-associated Infiltrative Keratitis (CLAIK) With Multipurpose Solutions and Contact Lens Combinations. Invest Ophthalmol Vis Sci. 2011:E-Abstract 101.
6. Sacco AJ. Silicone hydrogel contact lenses, lens care and sterile infiltrates: Is there a connection? Poster presented at the Global Specialty Lens Symposium, Las Vegas; 2011.