Collie Eye Anomaly (CEA) is a recessively inherited eye disorder that causes abnormal development of the choroid - an important layer of tissue under the retina of the eye. Sadly there is no treatment or cure for CEA.
The symptoms and signs can vary greatly among affected dogs within one breed, between parent and offspring and even within a litter.
The primary problem is choroidal hypoplasia (CH). There is under-development (hypoplasia) of the eye tissue layer called the choroid.
CEA can affect either one or both eyes.
Complications of severe disease can lead to vision loss, although this disorder only rarely threatens total blinding severely affected dogs, approximately 25% of dogs with CEA/CH, there are related problems with the health of the eye that can result in serious vision loss in some cases.
Colobomas are seen at and near the optic nerve head as outpouchings or “pits” in the eye tissue layers.
Colobomas can lead to secondary complications such as partial or complete retinal detachments and/or growth of new but abnormal blood vessels with hemorrhage – bleeding inside the eye.
This happens in 5-10% of dogs with CEA/CH, generally by 2 years of age, and ness.
A dog with one mutant copy and one normal copy of the CEA/CH gene is a carrier – is heterozygous. A dog with two copies of the normal CEA/CH gene is homozygous normal.
It is important to understand a carrier is not affected by this disease but if bred with another carrier, puppies will be affected.
A mating between a carrier and a clear dog will result in some puppies being clear and others being carriers but no puppies will be affected.
When both parents are clear all puppies will be clear by parentage.