In May 2006, the Illinois Department of Public Health (IDPH) informed CDC about a possible increase in Acanthamoeba keratitis (AK) at an ophthalmology center in Illinois during the preceding 3 years. The University of Illinois at Chicago (UIC) was investigating this possible increase. In October 2006, IDPH updated CDC about the ongoing UIC investigation. At that time, CDC informally contacted multiple ophthalmology centers in the United States to assess whether the potential increase in cases extended beyond Illinois. Responses from the ophthalmology centers were inconclusive. In January 2007, CDC initiated a retrospective survey of 22 ophthalmology centers nationwide to assess whether cases were increasing throughout the United States. In March 2007, data received from 13 centers demonstrated an increase in culture-confirmed cases of AK with wide geographic distribution. The increase in cases had begun in 2004 and continued to the present. On March 16, 2007, CDC initiated a multistate investigation to look for risk factors associated with this increase in AK cases. This report summarizes recent preliminary results of that investigation, which, indicated an association with AK in soft contact lens wearers who used Advanced Medical Optics (Santa Ana, California) Complete[R] MoisturePlus[TM] (AMOCMP) multipurpose cleaning solution. CDC and the Food and Drug Administration (FDA) are taking steps to notify the public and the medical and public health communities of this preliminary association. The manufacturer has undertaken a voluntary recall of the product.

AK, a rare but potentially blinding infection of the cornea, is caused by a ubiquitous, free-living ameba (Acanthamoeba) that is found commonly in the environment, including water (e.g., tap and recreational water), soil, sewage systems, cooling towers, and heating/ventilation/air conditioning (HVAC) systems. AK primarily affects otherwise healthy persons who wear contact lenses; an estimated 85% of U.S. cases occur in contact lens wearers (including wearers who follow recommended contact lens-care practices) (1). Persons who improperly store, handle, or disinfect their lenses (e.g., by using tap water or homemade solutions for cleaning); swim, use hot tubs, or shower while wearing lenses; come in contact with contaminated water; have minor damage to their corneas; or have previous corneal trauma are at increased risk for infection (2). Based on an analysis of cases reported to CDC during 1985-1987, the incidence of AK in the United States has been estimated at one to two cases per million contact lens users (3,4). An estimated 30 million persons in the United States wear soft contact lenses (5).

Initial case finding for this investigation was facilitated through postings on the Epidemic Information Exchange (Epi-X), on ophthalmology/optometry/infection control listservs and websites, and through queries of clinical microbiology laboratories. As of May 24, 2007, a total of 138 patients with onset of symptoms on or after January 1, 2005, and positive Acanthamoeba cultures from corneal specimens had been reported to CDC by public health authorities and ophthalmologists from 35 states and Puerto Rico. Standardized telephone interviews of patients, ophthalmologists, and primary eye-care providers are being conducted by state and local health officials and CDC. Laboratory testing of clinical specimens, contact lenses, bottles of solution, and contact lens cases received from AK patients, including typing of Acanthamoeba spp. isolates, is ongoing. An initial analysis was conducted using data from the first 46 completed patient interviews.

Among the 46 culture-confirmed patients who were interviewed, the median age was 40 years (range: 15-77 years); six (13%) were aged <18 years. Twenty-seven (59%) were female. Of the 37 of these patients for whom clinical data were available, medical therapy was unsuccessful for nine (24%), and they were required or expected to undergo corneal transplantation. Of the 46 patients, 39 (85%) wore soft contact lenses, three (7%) wore rigid lenses, and four (9%) reported no contact lens use. Among the 42 contact lens users, 16 (38%) reported swimming while wearing contact lenses and 35 (83%) reported showering while wearing contact lenses during the month before symptom onset.

Among the 39 soft contact lens users, 36 reported using one or more specific types of contact lens solution, 21 of these (58%) reported any use of AMOCMP in the month before symptom onset, 20 (56%) reported using AMOCMP as their primary solution, and 14 (39%) reported using AMOCMP as their exclusive solution. Exposure data from the 36 patients who wore soft contact lenses and used any type of contact lens solution were compared with exposure data from controls who were interviewed as part of the 2006 CDC Fusariurn keratitis outbreak investigation (6). These controls, who were selected as geographically matched controls for the Fusarium keratitis cases, represented a sample of adult soft contact lens wearers from different U.S. states who were asked about product use and behaviors during March 2006 (6).