Nearly 1 million clinical visits for keratitis occur annually. The largest single risk factor for microbial keratitis is contact lens wear. Among the estimated 38 million contact lens wearers in the United States, poor storage case hygiene, infrequent storage case replacement, and overnight lens wear are established preventable risk factors for microbial keratitis, contact lens–related inflammation, and other eye complications.[3,6,7]
In this analysis, the proportion of visits varied by age and sex. This likely reflects differences in contact lens use and inclination toward seeking health care as well as differences in risk factors for keratitis. The incidence of microbial keratitis reported previously ranged from 0.4 to 5.2 per 10,000 person-years for rigid gas-permeable and soft contact lens wearers to >20 per 10,000 person-years for overnight soft contact lens wearers; one population-based study in California estimated that 71,000 cases of severe microbial keratitis could occur per year. This study is the first attempt to characterize the overall burden of keratitis on the U.S. health care system. To help direct future prevention efforts for microbial keratitis, the current epidemiology of keratitis in the United States and its impact on the U.S. health care system must be understood and quantified. Additionally, development and dissemination of effective prevention messages to contact lens users is essential.
The findings in this report are subject to at least four limitations. First, the estimated prevalence of visits for keratitis-related diagnostic codes is likely to be an underestimate, because the datasets used in this analysis capture few visits to optometrists. Although most persons with sight-threatening cases of microbial keratitis would be expected to visit an ophthalmologist, persons with less complicated infections might only interact with an optometrist, and those visits would not be included in the datasets used. Second, not all keratitis visits were for microbial keratitis; some keratitis does not result from infection. Many ICD-9-CM codes for keratitis identify keratitis by anatomic location (e.g., central corneal ulcer compared with marginal corneal ulcer) rather than by etiologic agent; therefore, visits that involved microbial keratitis could not be specifically identified. Although a large percentage of patients received antimicrobial treatment, and ICD-9-CM codes specific for noninfectious keratitis were excluded from the analysis, the proportion of keratitis caused by infectious agents is unknown. The percentage of patients receiving antimicrobial treatment is likely an underestimate because Marketscan does not record prescriptions not covered by insurance (i.e., compounded prescriptions or prescriptions that cost less than the copay amount). Third, this analysis was not able to directly identify contact lens wearers. Some visits for keratitis likely occurred among persons who do not wear contact lenses, but that proportion is unknown. Conversely, visits for corneal disorders involving contact lens wear are not all caused by microbial keratitis (e.g. an unknown proportion were caused by corneal abrasions), although the majority received topical antimicrobials. Finally, because the demographics of contact lens wearers in the United States are not known, rates of visits by age or sex among contact lens wearers could not be calculated.
Keratitis associated with poor contact lens hygiene is preventable. Prevention efforts should include surveillance, improved estimates of the burden of disease, and vigorous health promotion activities focused on contact lens users and eye care professionals (ophthalmologists, optometrists, and opticians). Increased surveillance capacity is needed for microbial keratitis, in particular data from optometrist visits. Current recommendations for proper contact lens wear and care are available ( Box ).¶
¶Available at https://www.cdc.gov/contactlenses.
Morbidity and Mortality Weekly Report. 2014;63(45):1027-1030. © 2014 Centers for Disease Control and Prevention (CDC)