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

Overview

• This study evaluates environmental and demographic risk factors associated with corneal ulceration in horses presenting to emergency veterinarians in the Western United States over a three-and-a-half-year period.
• It identifies specific factors linked to the occurrence of corneal ulcers and assesses which factors increase the likelihood of severe outcomes, such as the need for eye removal (enucleation).

Study Purpose and Design

• The main goal was to understand how environmental conditions and horse-specific characteristics relate to the frequency and severity of corneal ulcers in horses.
• The research was a retrospective study, analyzing documented cases from May 2020 to November 2023.
• Cases were drawn from equine field and hospital practices in the Western United States, providing a regional context.
• A total of 420 horses diagnosed with corneal ulceration (via clinical examination and fluorescein staining) formed the study population.

Methods

• The study collected clinical data on the horses, including age, sex, ulcer characteristics (such as depth and which eye was affected), and complications like uveitis.
• Environmental data included average wind speed, temperature, and dew point around the time of ulcer presentation.
• A Poisson regression model was used to analyze associations between these factors and the prevalence of corneal ulcer cases.
• Outcomes assessed included:
  • The correlation between environmental factors and corneal ulceration rates.
  • Factors predicting the need for enucleation (surgical removal of the eye).

Key Findings on Corneal Ulceration Risk

• Higher average wind speeds were significantly associated with increased incidence of corneal ulcers (p < 0.01), suggesting windy conditions may contribute to eye injury or inflammation.
• Increased average temperature showed a trend toward higher ulcer rates (p = 0.08), indicating warmer weather may also be a risk factor.
• Male horses had a higher likelihood of developing corneal ulcers compared to females (p = 0.004), highlighting a possible sex-related susceptibility or exposure.
• Dew point as an environmental factor was not specifically reported to have a significant association.

Factors Associated with Severe Outcomes (Enucleation)

• Older horses were at significantly increased risk of needing enucleation (p < 0.0001), implying that age may affect healing or severity.
• Deeper ulcers were strongly linked to enucleation risk (p < 0.0001), indicating that ulcer severity is critical in determining outcomes.
• The left eye involvement was slightly more associated with enucleation (p < 0.05) though the clinical relevance may require further investigation.
• The presence of uveitis (inflammation of the eye’s middle layer) was also significantly related to higher enucleation rates (p = 0.002), reflecting more severe ocular disease.

Clinical Implications

• Veterinarians working in equine emergency care, especially in the Western US, should be vigilant about increased corneal ulcer risk during periods of high wind and warmer temperatures.
• This awareness may guide preventative strategies, earlier diagnosis, or more aggressive management during high-risk environmental conditions.
• Older horses and those presenting with deep ulcers or uveitis require careful monitoring, as they have a higher probability of poor outcomes including eye loss.
• Sex differences in ulcer risk may point to the need for targeted educational or management strategies for male horses.

Study Strengths and Limitations

• Strengths:
  • Large sample size (420 cases) providing robust data.
  • Use of objective clinical confirmation of ulcers via fluorescein staining.
  • Combination of clinical and environmental data analyzed quantitatively with regression modeling.
• Limitations:
  • Retrospective design may introduce biases related to record completeness or regional practice variations.
  • Environmental data likely aggregated and may not capture individual exposure variations.
  • No detailed analysis of management or treatment approaches that could influence outcomes.

Summary

• This study highlights that environmental factors like wind speed and temperature contribute to the occurrence of corneal ulcers in horses.
• Male horses, increasing age, ulcer depth, and complications such as uveitis are important determinants for severe disease outcomes requiring enucleation.
• These findings can inform veterinarians and horse owners about risk periods and clinical features that warrant prompt intervention to prevent vision loss.