Collie eye anomaly
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Collie eye anomaly (CEA) is a congenital, inherited, bilateral eye disease of dogs involving the retina, choroid, and sclera. It can be a mild disease or cause blindness. CEA is caused by a simple autosomal recessive gene defect. It is known to occur in Smooth and Rough Collies, Shetland Sheepdogs, Australian Shepherds, Border Collies, and Nova Scotia Duck Tolling Retrievers[1]. Frequency is high in Collies and Shetland Sheepdogs, and low in Border Collies[2] and Duck Tollers[1].
The most common sign of CEA is the presence of an area of undeveloped choroid lateral to the optic disc, also known as choroidal hypoplasia. The choroid is a collection of blood vessels supplying the retina. CEA can also cause retinal or scleral coloboma, coloboma of the optic disc, retinal detachment, or intraocular hemorrhage. It can be diagnosed by fundoscopy by the age of six or seven weeks.[2] There is no treatment.
Controversies exist around eliminating this disorder from breeding Collies. Some veterinarians advocate only breeding dogs with no evidence of disease, but this would eliminate a large portion of potential breeding stock. Because of this, others recommend only breeding mildly affected dogs, but this would never completely eradicate the condition. Also, mild cases of choroidal hypoplasia may become pigmented and therefore undiagnosable by the age of three to seven months. If puppies are not checked for CEA before this happens, they may be mistaken for normal and bred as such. Checking for CEA by seven weeks of age can eliminate this possibility. Diagnosis is also difficult in dogs with coats of dilute color because lack of pigment in the choroid of these animals can be confused with choroidal hypoplasia. Also, because of the lack of choroidal pigment, mild choroidal hypoplasia is difficult to see, and therefore cases of CEA may be missed.[2]
Until recently, the only way to know if a dog was a carrier was for it to produce an affected puppy. However, a genetic test for CEA became available at the beginning of 2005, developed by the Baker Institute for Animal Health, Cornell University, and administered through OptiGen.[3] The test can determine whether a dog is affected, a carrier, or clear, and is therefore a useful tool in determining a particular dog's suitability for breeding.
[edit] References
- ^ a b Nova Scotia Duck Tolling Retriever Club (USA). Collie Eye Anomaly Discovered In The Nova Scotia Duck Tolling Retriever. Retrieved on 2006-05-26.
- ^ a b c Gelatt, Kirk N. (ed.) (1999). Veterinary Ophthalmology, 3rd ed., Lippincott, Williams & Wilkins. ISBN 0-683-30076-8.
- ^ American Border Collie Association. Health and Genetics of Border Collies - A Breeder and Buyer's Guide. Retrieved on 2006-07-28.
