ACANTHAMOEBA, BACTERIAL, AND FUNGAL CONTAMINATION OF CONTACT-LENS STORAGE CASES

Background-Microbial corneal infection is the most serious complication of contact lens wear. Contact lens cases are a recognised potential source of pathogens associated with corneal ulcers. Methods-This survey established the incidence of protozoal, bacterial, and fungal contact lens case contamination in 101 asymptomatic daily wear cosmetic contact lens wearers from a domiciliary contact lens practice. Results-Eighty two (81%) contact lens cases were found to be contaminated, with 19 (19%) sterile. Of all contact lens cases, 78 (77%) grew bacteria, 24 (24%) fungi, and 20 (20%) protozoa. Acanthamoeba spp were isolated from eight (8%) contact lens cases. Fifty six (55%) contact lens cases yielded mixed bacterial contamination, This is the first contact lens case survey in which hydrogen peroxide disinfection was the major method of contact lens disinfection (75% of subjects) and no home made saline was used. All the contaminating organisms were shown to possess the enzyme catalase that breaks down hydrogen peroxide to oxygen and water. The polymicrobial nature of the biofilms found in many contact lens cases is illustrated electron micrographically. Conclusion-Based on data from this and previous studies, the authors conclude with recommendations for contact lens wearers: (1) regular scrubbing of contact lens case interior to disrupt biofilms; (2) exposure of contact lens case to very hot water (greater than or equal to 70 degrees C) will kill Acanthamoeba contaminants; (3) allow contact lens case to air dry between uses; (4) if hydrogen peroxide disinfection is preferred, use a two step system; (5) replace contact lens case regularly.