Name one major complication associated with prolonged topical corticosteroid use in equine eyes.

• A. Corneal thinning/melt.
• B. Improved tear film stability.
• C. Hyperhydration of cornea.
• D. Decreased risk of infection.

Answer: (A)

Prolonged topical corticosteroid use in the equine eye most commonly leads to thinning and potential melting of the corneal stroma. This happens because steroids slow normal corneal wound healing by reducing keratocyte activity and collagen synthesis, and they dampen inflammatory processes that help organize repair. In the setting of an epithelial defect or ulcer, the suppression of healing combined with ongoing proteolytic enzyme activity and possible infection allows the corneal collagen to be degraded, leading to thinning, descemetoceles, or even perforation. Clinically this is a major concern in horses, so steroids are used with great caution around corneal ulcers and often avoided when infection (especially fungal) is suspected.

These drugs do not improve tear film stability, do not cause corneal hyperhydration, and do not reduce infection risk; in fact, they can predispose to infections by suppressing local immunity and delaying healing.