What is collie eye anomaly?
Collie eye anomaly (CEA), also called “collie eye defect” is an inherited, developmental disease in dogs. Predisposed breeds include:
- Shetland sheepdogs
- Australian shepherds
- Border collies
- Nova Scotia duck tolling retrievers
In CEA, there is a mutation of the gene that determines the development of the eye. This results in defects of many layers of the eye.
What are the clinical signs of CEA?
The most common sign of CEA is blindness. The degree of vision loss can vary, depending on the severity of the developmental defects. Many dogs have normal vision, but vision loss or blindness can occur, especially if the dog's retinas have detached.
CEA may be associated with several, more obvious abnormalities in the eye. “Microphthalmia” describes eyeballs that are smaller than normal. “Enophthalmia" describes eyeballs that are sunken deep into the eye sockets. Both of these abnormalities can be associated with CEA.
How is CEA diagnosed?
Many dog breeders screen for this anomaly, with examinations performed by a veterinary ophthalmologist between 6 and 8 weeks of age. Unfortunately, in some cases, CEA is not diagnosed until the dog's vision is affected. CEA may be diagnosed by your veterinarian through evaluating the retina, located at the back of the eye with the pupil dilated. Your veterinarian may also recommend referral to a veterinary ophthalmologist, for a complete eye examination. There may be areas of thinning (choroidal hypoplasia) or an actual hole, called a coloboma, in some of the structures of the eye. CEA may also be associated with a detached retina, which can occur as a complication of a coloboma.
Is there any treatment for CEA?
Unfortunately, CEA cannot be reversed. In the case of coloboma-induced partial retinal detachment, laser surgery may be attempted to re-attach the retina if the condition is detected early, Coloboma may not always lead to retinal detachment, particularly if the coloboma remains stable during the dog’s first year of life.
Can you prevent CEA?
Because CEA is a genetically-based developmental disease, it can only be prevented by not breeding dogs who carry the abnormal gene. There are now several genetic tests for CEA. Consult your veterinarian if you are planning to breed your dog to determine which pre-breeding tests are recommended.