My dog was always squinting with runny eyes. My veterinarian said he had entropion, where the edges of the eyelids turn into the eyeball and cause irritation. He performed an operation that corrected the problem. A friend told me only one or two breeds of dog can get this condition and usually not mixed breeds like mine. The skin of the eyelids usually has hair, along with eyelashes, that contacts the cornea and causes degrees of irritation, pain, tearing and squinting.
Many breeds have an inherited predisposition to developmental entropion.
They include Shar-Pei, chow chow, English and American cocker spaniel, St. Bernard, bull mastiff, Labrador retriever, Great Dane, Irish setter, collie, elkhound, smooth collie, bloodhound, Shetland sheepdog, Newfoundland, Neopolitan mastiff, Doberman pinscher, toy and miniature poodle, and Rottweiler. Other breeds as well as mixed breeds may be affected sporadically. Veterinarians usually treat developmental defects successfully with one of several surgical corrective techniques. A diagnosis by your veterinarian is essential because some young animals with excessive eyelid tissue may grow out of it. Some of these animals need only temporary correction with specially placed sutures, which allow normal function and limit eye irritation.