Factors Associated With Corneal Ulceration in Horses: 420 Cases (2020–2023)

OBJECTIVE: To evaluate how environmental and other risk factors are associated with the prevalence of corneal ulceration in horses presenting to equine emergency veterinarians in the Western United States. DESIGN: Retrospective study conducted from May 2020 to November 2023. SETTING: Equine field and hospital practice in the Western United States. ANIMALS: Four hundred twenty horses with corneal ulceration, confirmed by clinical examination and fluorescein staining, of any underlying cause. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary study outcomes were the association between environmental factors (wind speed, temperature, dew point) and corneal ulceration, as well as factors associated with the need for enucleation. Using a Poisson regression model, increased average wind speed (p < 0.01) and increased average temperature (p = 0.08) were associated with higher rates of corneal ulceration. Male horses were more likely to develop ulcers (p = 0.004) compared with females. Older age (p < 0.0001), deeper ulcers (p < 0.0001), and involvement of the left eye (p < 0.05) were associated with an increased risk for enucleation. The presence of uveitis was also associated with the need for enucleation (p = 0.002). CONCLUSIONS: Equine emergency veterinarians should be aware that both wind speed and increasing temperatures are associated with corneal ulceration in the Western United States. Enucleation in horses with corneal ulcers is associated with increasing age, uveitis, and increasing depth of the ulcer.