Microbial Keratitis and the Role of Rub and Rinsing Victoria Butcko, O.D., F.A.A.O., Timothy T. McMahon, O.D., F.A.A.O., Charlotte E. Joslin, O.D., F.A.A.O., and Lyndon Jones, Ph.D., F.C.Optom., F.A.A.O. Recent outbreaks of microbial keratitis in contact lens wearers have involved various pathogens, including Acanthamoeba and Fusarium species. Specific reasons for the marked increase in microbial keratitis, particularly those involving species typically rarely involved in contact lens infection, remain unknown. Possi- ble contributing factors include inadequacies of various multipur- pose solutions against certain pathogens; inadequate lens care hygiene, including elimination of the digital rubbing step; poor contact lens storage case hygiene; and the introduction of new soft contact lens materials that may promote adherence of certain pathogens, particularly when a digital rubbing step is eliminated. Although there is some conflict of opinion in the literature regard- ing the necessity for a mechanical rub during lens cleaning and disinfection, growing evidence supports the reestablishment of a digital rub component to multipurpose solution lens care systems. This article reviews the literature on whether such a process should be recommended to contact lens wearers. Key Words: Acanthamoeba—Contact lens hygiene—Digital rub—Fusarium—Multipurpose solution—Rub and rinse. Recent outbreaks of microbial keratitis in contact lens wearers have involved Acanthamoeba and Fusarium species, 1,2 which historically have been involved only rarely in cases of contact lens–associated microbial keratitis. 3,4 These outbreaks may have been associated with the improper use of certain multipurpose solutions, 5 with two multipurpose solutions having been identified as major contributing factors to the risk of microbial keratitis. 2–6 Specific reasons for the increase in microbial keratitis are un- known, but possible contributing factors include inadequacy of the multipurpose solution against certain pathogens, including Fusar- ium and Acanthamoeba; inadequate lens care hygiene, including the elimination of the digital rubbing technique; poor contact lens storage case hygiene; and the introduction of new soft contact lens materials that may promote adherence of certain pathogens when a digital rub step is eliminated. This article attempts to address these issues with a comprehensive review of the recent literature on the topic and specifically address the question of whether a digital rub should be reinstated as part of lens care regimens. Questions arise concerning the effectiveness of various multi- purpose solutions against certain pathogens, including Fusarium species and Acanthamoeba and the possible contribution to the increase of cases of microbial keratitis. The outbreak of Fusarium keratitis among patients wearing hydrogel contact lenses was directly linked to the use of one specific multipurpose solution, namely ReNu with MoistureLoc (Bausch & Lomb, Rochester, NY). 2,5 As of June 30, 2006, 115 (70%) of 164 confirmed cases of Fusarium keratitis were associated with ReNu with MoistureLoc. 5 Although ReNu with MoistureLoc successfully passed all the requirements of the U.S. Food and Drug Administration for mul- tipurpose solution marketing, this testing did not include evaluat- ing its effectiveness against Fusarium species or Acanthamoeba. Under stressed conditions, including improper hygiene and im- proper care of contact lenses, cases, and solution bottles, ReNu with MoistureLoc was actually found to support the growth of certain Fusarium strains in a dried crystalline form. 5,7 Many studies have attempted to evaluate the effectiveness of different multipurpose solutions and hydrogen peroxide solutions against Acanthamoeba. Hiti et al. 8 concluded that one-step hydro- gen peroxide systems do not have sufficient effects on Acan- thamoeba cysts because of the rapid hydrogen peroxide neutral- ization. Hydrogen peroxide systems that involved two steps, in which the soaking time in 3% peroxide was significantly longer, showed much higher efficacy than the one-step hydrogen peroxide solutions. 8 Borazjani and Kilvington 9 found that use of a poly- hexamethylene biguanide (PHMB)–preserved system (ReNu MultiPlus Multi-Purpose Solution; Bausch & Lomb), even in the presence of organic soil and when used in a no-rub protocol, effectively reduced the binding capacity of Acanthamoeba to contact lenses. However, the digital rubbing step with this study was supplemented by a specific and extensive rinsing technique. 9 Further work by Hiti et al. 10 showed that after exposure to various soft lens solutions, Acanthamoeba cysts were still viable in test situations, even after an 8-hour soaking time. The work by Hiti et al. 10 also addressed the efficacy of soft lens and rigid gas-perme- able lens multipurpose solutions against cysts of three specific strains of Acanthamoeba. Ten solutions were tested, with soaking times of 1 and 8 hours. The rigid gas-permeable lens solution, Boston Advance (0.0005% polyaminopropyl biguanide/0.003% gluconate), showed the greatest amoebicidal efficacy, with all From the Department of Ophthalmology and Visual Sciences (V.B., T.T.M., C.E.J.) and the Department of Epidemiology and Biostatistics, School of Public Health (C.E.J.), University of Illinois at Chicago, Chi- cago, IL; and the School of Optometry (L.J.), University of Waterloo, Waterloo, Ontario, Canada. Conducted at and supported by Alcon Research, Inc., Fort Worth, TX and supported by Bausch & Lomb, Inc., Rochester, NY. Address correspondence and reprint requests to Dr. T.T. McMahon, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612; e-mail: timomcma@uic.edu DOI: 10.1097/ICL.0b013e318157f3df Eye & Contact Lens 33(6): 421–423, 2007 © 2007 Contact Lens Association of Ophthalmologists, Inc. 421