Abstract and Introduction
Keratitis, inflammation of the cornea, can result in partial or total loss of vision and can result from infectious agents (e.g., microbes including bacteria, fungi, amebae, and viruses) or from noninfectious causes (e.g., eye trauma, chemical exposure, and ultraviolet exposure). Contact lens wear is the major risk factor for microbial keratitis;[1–3] outbreaks of Fusarium and Acanthamoeba keratitis have been associated with contact lens multipurpose solution use,[4,5] and poor contact lens hygiene is a major risk factor for a spectrum of eye complications, including microbial keratitis and other contact lens–related inflammation.[3,6,7] However, the overall burden and the epidemiology of keratitis in the United States have not been well described. To estimate the incidence and cost of keratitis, national ambulatory-care and emergency department databases were analyzed. The results of this analysis showed that an estimated 930,000 doctor's office and outpatient clinic visits and 58,000 emergency department visits for keratitis or contact lens disorders occur annually; 76.5% of keratitis visits result in antimicrobial prescriptions. Episodes of keratitis and contact lens disorders cost an estimated $175 million in direct health care expenditures, including $58 million for Medicare patients and $12 million for Medicaid patients each year. Office and outpatient clinic visits occupied over 250,000 hours of clinician time annually. Developing effective prevention messages that are disseminated to contact lens users and investigation of additional preventive efforts are important measures to reduce the national incidence of microbial keratitis.
Because a specific International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code for microbial keratitis does not exist, a set of keratitis-related codes that could apply to microbial keratitis patients was developed with clinician input. Codes included corneal ulcer (370.0), other forms of keratitis resulting from an underlying condition (370.8 used in conjunction with a second diagnostic code for the underlying condition [e.g., Acanthamoeba or Fusarium infection]), unspecified keratitis (370.9), and corneal disorders involving contact lens use (371.82). For office and outpatient visits, "contact lens problems" as a reason for the visit also were included in the contact lens category. The 2010 Marketscan Commercial Claims and Encounters database* was used to characterize the number of visits per person and episode length of keratitis and contact lens related–problems in 2010. The Marketscan Commercial, Medicare, and Medicaid databases also were used to estimate costs per visit for office, outpatient, or emergency department visits that did not result in hospital admission for keratitis, by insurance source. Data from the 2006–2010 National Ambulatory Medical Care Survey (NAMCS), National Hospital Ambulatory Care Medical Survey of Outpatient Departments (NHAMCS-OPD),† and 2010 Nationwide Emergency Department Sample§ were used to generate annual estimates of office, outpatient, and emergency department visits for the ICD-9-CM codes of interest. Statistical software was used to apply sampling weights and account for the complex sample design of these surveys. To estimate the total cost of annual visits, the total number of annual visits was multiplied by the cost per visit.
In 2010, the mean cost of a visit to a doctor's office for a keratitis-related diagnostic code was $151, and the mean cost of an emergency department visit was $587 ( Table 1 ). Most patients in 2010 made only a single visit, but a small proportion had numerous follow-up visits (maximum 49 total visits). Based on NAMCS and NHAMCS-OPD data, an estimated 700,000 doctor's office and outpatient clinic visits for keratitis occurred in 2010, including 280,000 visits for corneal ulcers ( Table 2 ). The majority of visits (76.5%) were associated with antimicrobial prescriptions. Separately, an estimated 230,000 doctor's office and outpatient clinic visits for corneal disorders involving contact lenses occurred, with the majority (70.0%) resulting in antimicrobial prescriptions. Among emergency department visits, 19,000 visits for corneal disorders involving contact lenses and 41,000 visits for keratitis occurred in 2010, including 25,000 visits for corneal ulcers. Approximately 1% of office visits and 4% of emergency department visits involved both categories of diagnosis codes. Women made 63.3% of office visits and 54.7% of emergency department visits. Persons aged <25 years made 20.5% of all visits, persons aged 25–44 years made 29.2% of visits, persons aged 45–64 years made 25.3% of visits, and persons aged ≥65 years made 25.1% of visits.
The total cost of the estimated 988,000 visits to doctor's offices, outpatient clinics, and emergency departments for keratitis and contact lens related diagnostic codes was $174.9 million, including $58.0 million in costs for Medicare patients and $11.9 million in costs for Medicaid patients ( Table 3 ). Office and outpatient clinic visits occupied over 250,000 hours of clinician time annually.
*The Marketscan Commercial Claims and Encounters, Medicare Supplemental, and Multistate Medicaid databases, from Truven Health analytics, include insurance claims and payments. Costs are the sum of 2010 insurer and out-of-pocket payments for office, outpatient, or emergency department visits per patient.
†CDC's national sample of visits to nonfederally employed, office-based physicians (NAMCS) and outpatient departments of nonfederal, general, and short-stay hospitals (NHAMCS-OPD), from the National Center for Health Statistics. Multiple years of data were used to increase sample size. Data for 2010 are the most recent year available.
§A national sample of hospital-based emergency department visits from the Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality.
Morbidity and Mortality Weekly Report. 2014;63(45):1027-1030. © 2014 Centers for Disease Control and Prevention (CDC)