Fungal Keratitis Prevalence Higher in Rural Areas than Non-Rural Areas

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A recent case series analysis found the fungal keratitis prevalence may be twice as high in rural compared with non-rural areas in the United States.

New estimates in a recent case series study suggest a two-fold higher prevalence of fungal keratitis among people living in rural areas than in non-rural areas in the United States.1

Among those living in rural areas, issues in access to eye care, stemming from disparities in obtaining appointments and receiving transportation to the appointment, could delay the diagnosis and treatment of keratitis.

“Given the potential for poor vision outcomes and the possibility of climate change-associated geographic expansion of pathogenic fungi, monitoring fungal keratitis trends, improving rural eye care access, and promoting early diagnosis and treatment are crucial,” wrote the investigative team led by Kaitlin Benedict, MPH, Centers for Disease Control and Prevention (CDC).

Approximately 1 million keratitis-related healthcare visits occur annually in the United States—nearly 6% of suspected infectious keratitis cases in the US are caused by fungi.2 Fungal keratitis risk factors, ranging from contact lens use to ocular trauma, have been well-defined. In this case series analysis, Benedict and colleagues sought to estimate the fungal keratitis prevalence among commercially insured patients in the US.1

The team used Merative MarketScan Commercial and Medicare Databases claims data submitted by health plans and large employers for ≥66 million people between January 2016 to January 2023. It defined fungal keratitis by ICD-10-CM code H16 for keratitis, continuous health insurance enrollment in the 14 days before and after the code, and a natamycin prescription in the continuous enrollment period.

Investigators also assessed selected medications, diagnoses, and procedures among patients enrolled 90 days before and after the first keratitis code.

Investigators identified 918,949 patients with a keratitis ICD-10-CM code, of which 870,810 (94.8%) met the 14-day continuous enrollment criteria. Among this population, 692 (0.8%) had a natamycin prescription. This population included 362 males (52.3%) and 330 females (47.7%), with a mean age of 47.5 years.

Upon analysis, the fungal keratitis prevalence overall was 1.8 per 100,000 enrollees. Higher prevalence rates were found among males (1.9 per 100,000 enrollees), adults ≥ 65 years (6.6 per 100,000 enrollees), and those living in the South (2.7 per 100,000 enrollees) and rural areas (3.6 per 100,000 enrollees).

Of 184 study participants (26.6%) with industry data, Benedict and colleagues found the rates were highest among the oil and gas extraction, and mining (2.9 per 100,000 enrollees), and manufacturing, durable goods (2.3 per 100,000 enrollees) industries.

In the 90 days before and after keratitis diagnosis, the most common conditions included corneal ulcer (n = 552 [94.2%]) and injury of the eye and orbit (n = 205 [35.0%]), while the most common medications included ophthalmic antibiotic (n = 473 [80.7%]), and ophthalmic corticosteroid use (n = 255 [43.5%]). The team identified 88 (15.0%) patients with contact lens-associated codes, including contact lens use and corneal disorders due to contact lenses, while 439 (74.9%) patients underwent a diagnostic test, and 62 (10.6%) patients received a corneal transplant.

Benedict and colleagues noted these data underpin the potential associations between fungal keratitis and certain industries and eye injuries among more than one-third of patients. The team noted the large number of patients prescribed ophthalmic antibodies indicates empirical treatment for suspected bacterial keratitis was initiated before laboratory results were made available.

“That more than 40% of patients were prescribed ophthalmic corticosteroids, which can worsen fungal keratitis, is concerning,” investigators wrote.


  1. Benedict K, Gold JAW, Smith DJ. Prevalence and Features of Fungal Keratitis Among US Patients With Commercial Health Insurance. JAMA Ophthalmol. Published online February 15, 2024. doi:10.1001/jamaophthalmol.2023.6825
  2. Ahmadikia K, Aghaei Gharehbolagh S, Fallah B, et al. Distribution, Prevalence, and Causative Agents of Fungal Keratitis: A Systematic Review and Meta-Analysis (1990 to 2020). Front Cell Infect Microbiol. 2021;11:698780. Published 2021 Aug 26. doi:10.3389/fcimb.2021.698780