Genetically-Based Eye Disease Prevalent in Collies

Tags: Collie Eye Anomaly, Health Problems, Health, CEA, Genetic Disorders, Eye Disorders

 

Many breeds of dog are vulnerable to specific health problems, and the Collie is no exception. These beautiful animals are subject to a genetically-carried eye problem known as Collie Eye Anomaly. It's a disorder that occurs deep within the eye and strikes all types of Collies.

Also known as choroidal hypoplasia, collie scleral ectasia syndrome and optic nerve/disc coloboma, it causes four main changes in the dog's eye. Specifically:

#1-The choroid is underdeveloped, a condition known as choroid hypoplasia. The choroid is a thin layer of blood vessels that deliver oxygen and nutrients to the retina (the portion of the eye which processes light signals and sends them to the brain to be interpreted as visual images).

#2-Colobomas, which are an oval- or diamond-shaped hole near the affected area.

#3-Thinning is found in the staphyloma, an area of tissue within the sclera, which is the white tissue adjacent to the choroid.

#4-In severe cases, CEA can contribute to retinal detachment, in which the retina comes loose and the dog loses vision in the affected eye.

In mild cases of collie eye anomaly the choroid is only slightly affected, and there is little impact on the dog's vision. These problems are fairly evenly divided. Twenty-five percent of all CEA cases display staphylomas; another 25 percent colobomas; and 25 percent choroidal dysplasia, with the remaining 25 percent having a combination of these problems. About 7 percent of all affected dogs will experience retinal detachment, which may or may not cause the dog to hemorrhage. When the retina is completely detached, the dog will be permanently blind in the affected eye.

Most dogs with CEA appear to have normal vision up until the point that a retinal detachment occurs, usually before the animal is two years of age. Veterinarians can diagnose the problem through a detailed eye exam, but there is no treatment.

CEA is passed along genetically through recessive genes, meaning two animals carrying the gene must produce puppies in order for the disease to appear. When it does, there is a wide range of impact. Border Collies, Rough- and Smooth-Coated Collies, and Shetland Sheepdogs are the most commonly affected. A similar genetic condition, although rare, has also been documented in Australian Shepherds, Beagles, Dachshunds, German Shepherds and both Miniature and Toy Poodles.

Collie owners are advised to obtain puppies only from breeders who are registered with the Canine Eye Registry Foundation or who can otherwise prove that their breeding animals do not carry the CEA gene. Any pups which are to be used for breeding should be examined at around five to six weeks of age, when a veterinarian should be able to diagnose the condition. Even mildly affected dogs should not be bred, since they carry the gene and their offspring may be born with a more severe form of CEA. Siblings of these dogs also should not be bred, unless a veterinarian can certify that they are unaffected.

comments powered by Disqus