Eye anomaly, also more commonly known as Collie Eye Anomaly or CEA, is found in all breeds of collies including the Smooth and Rough Collies, Shetland Sheepdogs, and Australian Shepherds. The condition also occurs to a lesser extent in the Nova Scotia Duck Tolling Retriever and some types of heelers.
CEA is a recessive genetic condition, which means that both parents have to be carrying the recessive gene for the condition to be passed down to their puppies. While this may sound like terrific news to eliminate the condition, the current estimate is that up to 85% of all collies in the United States are affected by this condition and that the numbers are almost as high in other countries and areas around the world.
CEA does not always affect the dog's vision and, in mild cases, may actually be undetectable after the puppy matures. This situation, known by vets and breeders as "going normal" is very difficult in breeding programs as unless the puppy was tested for the condition the adult will seem to have a clean bill of health when it comes to CEA, therefore being presented as free from the condition. Puppies should be tested at five to eight weeks and never later than eight to twelve weeks to detect CEA. The test is simple, a vet or veterinary ophthalmologist can test the eye with a light, looking for light patches and density differences in the back of the eye.
The biggest concern with CEA is the effect that the abnormal development of the choriod or the blood vessel rich layer that encircles the eye and provides blood to the retina will have on vision. In cases of CEA this layer is missing or very thin in some patches around the eye, resulting in visible sclera, which is the harder, outer layer of the eye. In serious cases the sclera will bulge, resulting in a condition known as a coloboma. When these pouches or bulges press against the optic nerve it can result in blindness, or pressure against the retina that will cause retinal detachment and bleeding in the eye. This can be treated with surgery but will require a veterinary ophthalmologist or surgical vet that is specially trained in this detailed type of surgery.
Mild cases of CEA do not become progressively worse with time and these dogs tend to learn to adjust to small blind spots in their vision without any noticeable change in their functioning or behavior. Since there are no signs of distress or discomfort and the dogs appear normal many backyard collie breeders that are not aware of the problem simply don't test, resulting in the continuation of the genetic condition. It is very important for breeders and purchasers to understand that breeding two collies with CEA will result in the puppies either being carriers of the condition or exhibiting the condition, there is no way for two dogs with CEA to produce a litter of puppies without CEA. While complete elimination of the condition will be extremely difficult, careful testing and very selective development of breeding lines will be essential to manage this condition within effected breeds.