Entropion is a genetic condition in which a portion of the eyelid is inverted or folded inward. This can cause an eyelash or hair to irritate and scratch the surface of the eye, leading to corneal ulceration or perforation. It can also cause dark-colored scar tissue to build up over the wound (pigmentary keratitis). These factors may cause a decrease or loss of vision.
Entropion is fairly common in dogs and is seen in a wide variety of breeds, including short-nosed breeds, giant breeds, and sporting breeds. Entropion is almost always diagnosed around the time a puppy reaches its first birthday.