Collie Eye Anomaly

What is Collie Eye Anomaly?

Collie Eye Anomaly is a congenital malformation of the choroid and retina in the eye. The choroid is the layer that supplies the eye with blood, and the retina is the layer that converts light into electrical signals that are sent to the brain. In dogs with CEA, these layers are not properly formed and can lead to various problems such as:

• Chorioretinal hypoplasia: This is a thin or missing area in the choroid or retina that is often visible as a bright spot in the back of the eye.
• Coloboma: This is a gap or defect in the choroid or retina, often located at the edge of the pupil. It can lead to bleeding or retinal detachment.
• Retinal detachment: This is a detachment of the retina from the choroid, which can lead to loss of vision or blindness.
• Staphyloma: This is a protrusion of the choroid through a thin area in the sclera (the white layer of the eye). It can lead to an enlarged or irregularly shaped eye.

Collie Eye Anomaly is a hereditary disease that is controlled by multiple genes. This means that a dog must inherit a defective gene from both its sire and dam in order to develop the disease. However, the disease can also occur in dogs that show no changes in the back of the eye but are carriers of the defective gene. These dogs can pass the disease on to their offspring.

Which dog breeds are affected by Collie Eye Anomaly?

Collie Eye Anomaly mainly occurs in dog breeds from the Collie family and related breeds. These include

• Long-haired Collie
• Short-haired Collie
• Shetland Sheepdog (Sheltie)
• Border Collie
• Australian Shepherd
• Lancashire Heeler

The incidence of the disease varies according to breed and breeding line. In long-haired and short-haired Collies, it is estimated that 80 to 90 percent of dogs have changes in the back of the eye without their vision being impaired. In Shelties, the frequency is around 70 percent. In Border Collies and Australian Shepherds, it is around 2 to 3 percent.

How do you recognize Collie Eye Anomaly in dogs?

The symptoms of Collie Eye Anomaly depend on the severity of the changes in the back of the eye. Many dogs with CEA have little or no visual impairment and show no signs of discomfort or pain. Other dogs with CEA may have reduced vision or blindness in one or both eyes. This may manifest itself in the following behaviors, for example:

• Uncertainty or fear in unfamiliar environments
• Stumbling or colliding with objects
• Difficulty catching toys or food
• Avoidance of dark rooms or stairs
• Staring or nodding their head

The only way to reliably diagnose Collie Eye Anomaly in dogs is to have the back of the eye examined by a veterinarian or a specialized ophthalmologist. This involves using a special lamp (ophthalmoscope) to view the choroid and retina. The examination should be carried out on all puppies of at-risk breeds at the age of 6 to 8 weeks before they are given to their new owners. The examination should also be repeated in adult dogs that are to be used for breeding.

How is Collie Eye Anomaly treated in dogs?

Unfortunately, there is no cure for Collie Eye Anomaly in dogs. The malformations in the back of the eye are irreversible and cannot be corrected. Treatment is therefore limited to alleviating symptoms and preventing complications.

In dogs with retinal detachments, laser treatment can be attempted in some cases to reattach the retina to the choroid. However, this can only be done for recent detachments and only for certain forms of coloboma. The success rate is not very high and the treatment is expensive and risky.

In dogs with staphyloma, surgery may be considered to reduce or remove the eye. This may be for cosmetic or medical reasons, for example if the eye is painful or inflamed.

However, most dogs with CEA do well without treatment. They adapt to their impaired vision and can lead a normal life. It is important that they have a loving and safe environment in which they feel comfortable. This includes, for example

• Good lighting in the home
• A clear arrangement of furniture and objects
• A familiar routine and fixed caregivers
• Appropriate stimulation and activity
• Regular checking of the eyes for signs of irritation or infection

The life expectancy of dogs with CEA is not reduced as long as they have no other health problems.

How to prevent Collie Eye Anomaly in dogs?

The only way to avoid Collie Eye Anomaly in dogs is to breed responsibly. This means that only dogs that are free of CEA or at least have no severe changes in the back of the eye should be used for breeding. In addition, only dogs with a known genetic status should be bred to each other. This means that they have either been tested or their parents have been tested.

There is a DNA test for CEA that can be carried out in specialized laboratories. The test is based on a gene called NHEJ1, which is responsible for the majority of cases of CEA. The test can give three possible results:

• Normal: The dog has two copies of the normal gene and is free of CEA.
• Carrier: The dog has one copy of the normal gene and one copy of the defective gene. It has no or only slight changes in the back of the eye, but can pass the disease on to its offspring.
• Affected: The dog has two copies of the defective gene and has changes in the back of the eye that can affect its vision.

However, the DNA test for CEA is not 100% reliable. There are some cases of CEA that cannot be explained by the NHEJ1 gene. This means that there are other genes that play a role in the development of the disease. Therefore, the DNA test should always be performed in combination with an ophthalmoscopic examination.

Breeding dogs with CEA should be avoided to reduce the risk to offspring. If a dog is a carrier or affected, it should only be bred to a normal dog. The puppies should then be tested and examined to determine their genetic status and severity of the disease.