Equine Corneal Ulcer Study Guide

Overview and Clinical Importance

Corneal ulcers (ulcerative keratitis) represent one of the most common and potentially vision-threatening ophthalmic emergencies in equine practice. Horses are uniquely predisposed to corneal disease due to their large, laterally positioned eyes with prominent corneas, inquisitive nature, and frequent exposure to environmental pathogens and trauma. The equine cornea is approximately 0.8-1.0 mm thick and consists of three primary layers: epithelium, stroma (comprising 90% of thickness), and endothelium with Descemet's membrane.

Unlike other domestic species, horses have a higher incidence of fungal keratitis (keratomycosis), particularly in warm, humid climates such as the southeastern United States. The avascular nature of the healthy cornea limits immune response and drug delivery, making aggressive treatment essential. Untreated or improperly managed corneal ulcers can progress to keratomalacia (melting), descemetocele formation, perforation, or endophthalmitis within 24-48 hours.

Etiology and Pathophysiology

Common Causes

Trauma: Direct corneal injury from hay, bedding, foreign bodies (thorns, plant material), stall fixtures, or rubbing. This is the most common initiating cause.