Collie Eye Anomaly

Collie eye anomaly (CEA) is a disorder characterized by abnormal development of the eye. It occurs predominantly in the collie breed, although it is also seen in the Shetland sheepdog, the Australian shepherd and the border collie. In some areas, it is estimated that up to 75 percent of collies are affected by the disease. 

In its mildest form, minor changes occur in the choroid, which is the vascular layer in the back of the eye. These changes have little effect on sight. CEA affects the retina, the choroid, and in severe cases, the sclera and optic nerve.

CEA is an inherited disease and most of the eye lesions associated with CEA are present at birth. But minor lesions may not be detectable on the eye examination after three months of age, so collies intended for breeding programs should be examined early at six to seven weeks of age. Even dogs with minor lesions should not be bred because their offspring may be affected with more serious forms of the disorder.

CEA is a simple recessive disorder. All affected animals have two genes for CEA; therefore, both of their parents are either affected dogs or carriers.

What to Watch For

Most dogs with CEA have no detectable changes in vision; however, if they have large lesions, they may have visual defects. 

Choroidal hypoplasia (CH). This is the inadequate development of the choroid, which is a thin layer of blood vessels that deliver oxygen and nutrients to the retina.

Coloboma. Colobomas are holes or craters in the posterior lining of the eye due to incomplete development of the fibrous coating of the eye. Most colobomas involve or are near the optic disk and are always accompanied by CH. Vision may be normal with small colobomas, but it is usually decreased or absent with large colobomas.

Tortuous or twisted blood vessels in the retina

Retinal detachment with or without hemorrhage, which occurs in the most severe cases. Detachments usually develop by 6 to 12 months of age. Dogs that develop retinal detachments in both eyes are blind.

Diagnosis

CEA is best diagnosed at between six and 12 weeks of age. CEA is diagnosed based upon the finding of any of the eye lesions described above.

The primary tool used to diagnose CEA is indirect funduscopy. This test examines the retina or fundus of the eye, which is the back portion of the interior of the eyeball. It involves examining the retina through the pupil using a lens and ophthalmoscope.

Treatment

Currently, there is no treatment for CEA. The major emphasis is placed on eliminating it from affected breeds.

Home Care and Prevention

Dogs with only choroidal hypoplasia or small colobomas do not need follow-up care. Dogs with retinal hemorrhages and large colobomas may be re-examined in two to three months to monitor for the development of retinal detachments.

The disease can best be prevented by breeding only normal dogs.