Collie eye anomaly

Collie eye anomaly (CEA) is a congenital, inherited, bilateral eye disease of dogs, which affects the retina, choroid, and sclera. It can be a mild disease or cause blindness. CEA is caused by a simple autosomal recessive gene defect. There is no treatment. Affected breeds 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. Frequency is high in Collies and Shetland Sheepdogs, and low in Border Collies and NSDTRs. 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. Pathogenesis CEA is caused by improper development of the eye. 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. The choroid, especially lateral to the optic disc, is hypoplastic (underdeveloped). A coloboma, or hole, may form in or near the optic disc due to a failed closure of embryonic tissue. The degree of these abnormalities varies between individual dogs, and even between the same dog's eyes. CEA is inherited as an autosomal recessive trait that has a penetrance reaching 100 percent, and has been localized to canine chromosome 37. Signs 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. 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. Severe cases may be blind.