Because of this, others recommend only breeding mildly affected dogs, but this would never completely eradicate the condition. Some veterinarians advocate only breeding dogs with no evidence of disease, but this would eliminate a large portion of potential breeding stock. Severe cases may be blind.Ĭontroversies exist around eliminating this disorder from breeding Collies. It can be diagnosed by fundoscopy by the age of six or seven weeks. CEA can also cause retinal or scleral coloboma, coloboma of the optic disc, retinal detachment, or intraocular hemorrhage. The choroid is a collection of blood vessels supplying the retina. The most common sign of CEA is the presence of an area of undeveloped choroid (appearing as a pale spot) lateral to the optic disc. CEA is inherited as an autosomal recessive trait that has a penetrance reaching 100 percent, and has been localized to canine chromosome 37. The degree of these abnormalities varies between individual dogs, and even between the same dog's eyes. A coloboma, or hole, may form in or near the optic disc due to a failed closure of embryonic tissue. The choroid, especially lateral to the optic disc, is hypoplastic (underdeveloped). Failure of the cells of the posterior portion of the optic vesicles to express growth hormone affects the differentiation of other cells of the eye. Pathogenesis ĬEA is caused by improper development of the eye. In the United States, incidence in the genotype of collies has been estimated to be as high as 95 percent, with a phenotypic incidence of 80 to 85 percent. Frequency is high in Collies and Shetland Sheepdogs, and low in Border Collies and NSDTRs. It is known to occur in Collies ( smooth and rough collies), Shetland Sheepdogs, Australian Shepherds, Border Collies, Lancashire Heelers, and Nova Scotia Duck Tolling Retrievers.
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