Julie Gionfriddo, DVM, DACVO ACVO Genetics Committee/CERF Liaison
There are numerous eyelid disorders in dogs. Entropian (rolling inwards), and ectropian (drooping or rolling outward) are the most common and, although they are considered abnormal eyelid conformations, are characteristics of many breeds. For example, droopy lower eyelids (ectropion) are usually present in Basset hounds and other hound breeds. The breeding of Shar Peis and Chow Chows, in which breeding selection has been made for numerous facial wrinkles, has led to turning in of the eyelids (both upper and lower in many cases).
Ectropian, unless very pronounced, does not lead to severe diseases of the eye itself. However, the droopy eyelid may collect debris such as dust, pollen and plant material from the environment. This may cause ocular irritation that leads to discharge and a red eye. This is particularly pronounced in hunting dogs or dogs that are outdoors much of the time. Dogs that have ectropion must be watched carefully by their owners for possible foreign bodies in their eyes, and the dogs' eyes must be cleaned and often medicated on a regular basis.
Entropion on the other hand frequently causes ocular pain and corneal disease. If the eyelid is rolled inward sufficiently so that the hairs of the eyelid rub on the eye, much damage may be done. Dogs with entropion usually squint and have watery eyes. If the entropion is not corrected and the rubbing continues, ulcers often develop on the cornea and the cornea becomes pigmented. Vision may be lost. Dogs that have had entropion correction surgery cannot be shown.
Although entropion and ectropion are hereditary disorders in many breeds, their mode of inheritance is complex. No one gene controls the development of eyelid conformation. Instead, it is a combination of genes that control eyelid size and shape, depth of the orbit (eye socket), size and shape of the eyes, head conformation and amount of facial skin. All of these genes work in concert to determine the relationship of the eyelids to the eye. Therefore if an eyelid conformation defect is to be eliminated, only those dogs without entropion or ectropin must be bred. In many cases this may be difficult as "abnormal" eyelids may be a desirable breed standard.
The current CERF recommendations for breeding dogs with ectropian is classified as a "breeder option". This is because, although it is a hereditary problem, it is usually not sight threatening. Entropion is a painful and potentially blinding disease and therefore affected dogs in breeds that have a high incidence of entropion (such as Bloodhounds, Chow Chows, English Bulldog, Bull Mastiff, Chinese Shar Pei, Mastiff, Vizsla, and Saint Bernards) are denied certification. (CERF NOTE: As of November 2001, entropion is breeder's option for Bloodhound, Bulldog, Bull Mastiff, Mastiff, Saint Bernards.) However, because exaggerated facial conformation with loose skin and/or heavy facial folds often leads to eyelids that roll in or out predisposed the animal to irritation, discomfort and possible vision loss, selecting away from these traits in all breeds is strongly encouraged.