Collie Eye Anomaly (CEA/CH) Testing Guide for Dogs

Collie Eye Anomaly (CEA), also known as Choroidal Hypoplasia (CH), is an inherited developmental eye disorder primarily affecting several dog breeds including collies, Shetland sheepdogs, Australian shepherds, Border collies, Lancashire heelers, and Nova Scotia duck tolling retrievers. This condition causes abnormal development of the choroid, a crucial tissue layer beneath the retina, leading to thinning or underdevelopment that can affect vision ranging from mild impairment to blindness.

Because it is a hereditary condition with autosomal recessive inheritance, genetic testing is essential for breeders to prevent passing on the disease. In this guide, we provide detailed knowledge about CEA/CH, the breeds at risk, the genetics behind it, and how to get your dog tested responsibly within a UK context.

Understanding Collie Eye Anomaly and Choroidal Hypoplasia

CEA manifests as an underdeveloped choroid layer, which supplies blood and nutrients to the retina. Unlike other eye conditions that develop over time, CEA is congenital, typically visible from a young age. The severity is highly variable - dogs within the same litter may present vastly different symptoms.

Many affected dogs retain normal or near-normal vision; however, severe cases may include retinal detachment, optic disc coloboma (a structural defect in the eye), microphthalmia (small eyes), enophthalmia (sunken eyes), and in rare cases, total blindness.

Diagnosis is usually via an eye examination by a veterinary ophthalmologist, carried out ideally between 6 to 8 weeks old. This early timing is crucial since some puppies may later appear "normal" due to the tapetum lucidum's development obscuring signs, a phenomenon known as the "go normal" effect.

Breeds Commonly Affected by CEA/CH

The condition predominantly affects dogs with collie heritage. Key susceptible breeds include:

• Smooth Collie
• Rough Collie
• Shetland Sheepdog
• Australian Shepherd
• Border Collie
• Lancashire Heeler
• Nova Scotia Duck Tolling Retriever

Other breeds such as Australian Cattle Dogs, English Shepherds, and Boykin Spaniels may also be affected, although less commonly.

How CEA/CH Heredity Works

CEA/CH is inherited in an autosomal recessive pattern, meaning a dog must inherit two copies of the mutated gene (one from each parent) to exhibit the condition. Dogs with only one copy are carriers and typically show no signs but can pass the mutation to their offspring.

The genetic classification after testing can be:

• Clear (N/N): No copies of the mutation, will not develop or pass on CEA.
• Carrier (N/CEA): One copy of the mutation, usually unaffected but can produce affected or carrier puppies if bred with another carrier or affected dog.
• Affected (CEA/CEA): Two copies of the mutation, at risk of displaying clinical signs and will pass the mutation to all offspring.

This explains why even clinically normal dogs may still pose a risk of spreading CEA within breed lines if used in breeding without testing.

Testing Your Dog for Collie Eye Anomaly

Step 1: Choose Appropriate Testing

There are two main ways to test for CEA:

• DNA testing: A simple and reliable genetic test done by laboratories that identifies if your dog is clear, carrier, or affected.
• Ophthalmic examination: An eye exam by a veterinary ophthalmologist typically performed early in puppyhood to identify clinical signs.

Step 2: Obtain a Sample

Your vet will collect a small blood sample from your dog, which is sent to an authorised laboratory licensed to perform CEA testing. This is a straightforward procedure usually done during routine health checks.

Step 3: Get Results and Interpret

Results typically indicate whether your dog is Clear, Carrier, or Affected. Clear dogs are safe for breeding regarding CEA gene. Carriers should be bred responsibly, ideally with Clear dogs, to prevent affected puppies. Affected dogs are generally advised against breeding to avoid propagating the condition.

Step 4: Make Responsible Breeding Decisions

Given the importance of maintaining genetic diversity, removing all carriers from breeding is not always advisable as this could cause other health issues through restricted gene pools. Instead, breeders use test results to make informed decisions, avoiding carrier-to-carrier matings and monitoring offspring health carefully.

Why is CEA/CH Testing Important?

CEA severity varies and mild cases can still pass on the faulty gene to offspring who may be more severely affected. Testing helps preserve the welfare of breeds prone to this disease and supports ethical, informed breeding. It is strongly recommended for owners and breeders of susceptible breeds to ensure the health and quality of future litters.

Where to Get Your Dog Tested

For a list of authorised UK laboratories and genetic testing services, visit the Kennel Club's DNA Testing Information page. Your veterinary surgeon can also assist in organising sample collection and submitting tests appropriately.

Summary and Next Steps

Collie Eye Anomaly is a complex inherited eye condition notably affecting several collie-related breeds in the UK. Its diagnosis and management depend on genetic testing and ophthalmic exams early in life. Responsible and informed breeding decisions grounded in testing results can significantly reduce the prevalence of this condition, helping maintain healthy, happy dogs in affected breeds.

If you own a susceptible breed or plan to breed, we advise consulting your vet for guidance on testing and consider joining health schemes to contribute to wider control efforts. Prioritising your dog's welfare and making ethical choices supports future generations free from preventable blindness.