Leave it to an equine corneal ulcer to ruin everybody’s day.

These painful defects are notoriously difficult to treat, mainly because veterinarians must understand the underlying destructive processes to manage them effectively—and the variety of pathogens that can be involved. To complicate things further, ulceration can expand and deepen in the absence of infection because of how the horse’s immune system on the surface of the eye responds. Worst-case scenario, ulcers can lead to the loss of vision or even the eye itself, if not properly managed in time.

An ulcer—technically, a loss of epithelium and stroma (the top two corneal layers) down to the third layer, Descemet’s membrane—“is a host response that has gone horribly wrong,” said Andrew Matthews, Hon Member ACVO, Dipl. ECEIM (Ret), FRCVS, an equine practitioner and ophthalmologist from Angus, Scotland. He described how to manage complicated corneal ulcer cases at the 2016 British Equine Veterinary Association Congress, held Sept. 7-10 in Birmingham, U.K.

A variety of factors can make ulcers “complicated,” he said, including:

  • Progressively getting worse despite aggressive therapy.
  • Fungal presence. Matthews noted that fungal ulcers are still relatively rare in the U.K., but occur in other parts of the world. Be suspicious of fungus when blood vessels approaching the ulcer as part of the healing response abruptly stop short of the ulcer.
  • Presence of certain bacteria, which can promote an aggressive host white blood cell response—called a polymorphonuclear neutrophil leucocyte (PMN) response&