Entropion refers to a disorder where the eyelid margin rolls in and irritates the surface of the eye. Perhaps the most common type of entropion seen involves the lateral lower eyelid or lateral canthus (where the upper and lower eyelids meet at the outer edge of the eye).
Entropion can occur because of excess skin around the eyes or where the eyelid margin is too large for the size of the eyeball. Another factor which has also been suspected is inappropriate tension in the ligament at the lateral canthus resulting in pulling in of the eyelid at the canthus. While entropion does not generally cause blindness, it results in considerable discomfort for the dog and needs to be surgically corrected often at great cost to the owner.