related terms: exophthalmos, lagophthalmos, macroblepharon
What is exposure keratopathy syndrome?
With this syndrome, there is chronic irritation of the surface of the eye (the cornea) because of increased evaporation of tears and increased corneal exposure. This is a result of a combination of anatomic features including exophthalmos (protrusion of the eyeball), lagophthalmos (inability to close the eyelids completely) and macroblepharon (an exceptionally large eyelid opening, often associated with lower lid entropion). The result is inadequate blinking, and therefore reduced protection for the eye. Affected dogs experience chronic discomfort and are prone to ulceration of the cornea.
It is important to note that these anatomic features are normal for certain breeds, as a result of selection by breeders and demand by the public for a particular facial conformation with very prominent eyes, heavy facial folds and/or droopy eyelids. For example, the breed standard for pugs calls for a round head "with very large, bold and prominent eyes."
To avoid problems such as exposure keratopathy syndrome, breeders and dog owners are encouraged to choose dogs with less exaggerated facial features.
How is exposure keratopathy syndrome inherited?
The syndrome is associated with a combination of anatomic features that are influenced by several genes affecting skull and facial conformation.
What breeds are affected by exposure keratopathy syndrome?
Exposure keratopathy syndrome can be seen in any of the breeds in which these conformation features are seen:
Exophthalmos and lagophthalmos occur in brachycephalic breeds due to the compact facial and skull conformation. These features are particularly noticeable in the Pekingese, Lhasa apso, pug, and Shih tzu.
Macroblepharon is seen in the American cocker spaniel, Basset hound, bloodhound, Cavalier King Charles spaniel, Clumber spaniel, Lhasa apso, mastiff, Newfoundland, Pekingese, pug, Saint Bernard, and Shih tzu.
These features are combined in the American cocker spaniel, Cavalier King Charles spaniel, Clumber spaniel, Lhasa apso, mastiff, Pekingese, pug, and Shih tzu, so that dogs of these breeds are particularly susceptible to exposure keratopathy syndrome.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
What does exposure keratopathy syndrome mean to your dog & you?
Signs of chronic corneal irritation include reddening of the eye, increased tears, and discomfort (pawing or rubbing the eye). Affected dogs are prone to eye injuries from environmental insults (dust, twigs, et cetera). Corneal ulcers may develop due to increased corneal exposure.
Over time, pigmentation of the cornea may occur in response to chronic irritation. This may eventually interfere with your dog's vision.
How is exposure keratopathy syndrome diagnosed?
The eyeballs are prominent and the eyes may be reddened from chronic irritation. If corneal ulceration has developed, the eye will be painful and your dog may paw or rub it. With lagophthalmos, you may notice that your dog's eyes do not close completely when s/he is asleep.
Your veterinarian may do a fluoroscein dye test to check for corneal ulceration.
How is exposure keratopathy syndrome treated?
Tear substitutes provide only temporary relief. Surgical correction to reduce the size of the eyelid opening (permanent partial tarsorrhaphy) is usually effective in protecting the cornea over the long term. Where other associated eyelid defects such as entropion are present, several surgeries may be required.
Corneal ulceration, if present, must also be treated.
Exposure keratopathy syndrome is one of the eye conditions that is a result of selection by breeders and a demand by the public for such features as excessively prominent eyes and heavy facial folds. A responsible breeding programme will choose animals for breeding with a more normal head conformation, so as to select away from these exaggerated facial features and the problems associated with them.
Any dog that has required surgical correction to treat this condition should not be used for breeding, and may not be exhibited in the show ring.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Where to find more information?
Slatter, D. 1993. Textbook of Small Animal Surgery. p. 856-889. W.B. Saunders Co. ,Toronto.
Copyright © 1998 Canine Inherited Disorders
Database. All rights reserved.
Revised: April 11, 2000.