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

Collie Eye Anomaly (CEA), also called Choroidal Hypoplasia (CH), is a genetic developmental eye disorder mainly found in certain dog breeds such as Collies, Shetland Sheepdogs, Australian Shepherds, Border Collies, Lancashire Heelers, and Nova Scotia Duck Tolling Retrievers. This condition involves abnormal formation of the choroid, a vital tissue layer under the retina, resulting in thinning or incomplete development that can affect eyesight from mild issues up to blindness.

Since CEA is inherited in an autosomal recessive manner, genetic testing plays a critical role for breeders to avoid transmitting the disorder. This guide shares essential information about CEA/CH, breeds at risk, the hereditary background, and the recommended testing approaches within the American veterinary context.

What is Collie Eye Anomaly and Choroidal Hypoplasia?

CEA causes the choroid layer—which provides blood and nutrients to the retina—to be underdeveloped. Unlike many eye diseases acquired later in life, CEA is congenital and usually visible during early puppyhood. The severity of symptoms can vary widely, even among siblings from the same litter.

Many afflicted dogs maintain normal or near-normal vision; however, serious cases may include retinal detachment, optic disc coloboma (an eye structural defect), microphthalmia (abnormally small eyes), enophthalmia (sunken eyes), and rarely complete blindness.

Diagnosis typically involves an eye exam by a veterinary ophthalmologist conducted ideally between 6 and 8 weeks of age in the USA. This timing is important because some puppies may later show apparently normal eyes due to retinal reflection changes, a phenomenon called the "go normal" effect.

Breeds Most Commonly Impacted by CEA/CH

CEA primarily affects dogs with Collie lineage. Key susceptible breeds in American dog communities include:

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

Additional breeds such as Australian Cattle Dogs, English Shepherds, and Boykin Spaniels may rarely be affected.

How CEA/CH Is Inherited

The disorder follows an autosomal recessive inheritance pattern, which means a dog must inherit two mutated genes (one from each parent) to show the condition. Dogs with only one mutated gene are carriers; they normally don’t display symptoms but can pass the gene to their puppies.

Post-testing, dogs will be classified as:

• Clear (N/N): No mutation copies; these dogs won’t develop or transmit CEA.
• Carrier (N/CEA): One mutation copy; typically unaffected but may produce affected or carrier pups if mated with a carrier or affected dog.
• Affected (CEA/CEA): Two mutation copies; likely to develop symptoms and transmit the gene to all offspring.

Because of this, clinically normal dogs can still carry risk genes that contribute to spreading CEA if breeding without prior testing.

Testing Your Dog for Collie Eye Anomaly

Step 1: Select the Right Testing Method

There are two primary testing approaches available in the USA:

• DNA testing: Popular and accurate genetic testing through authorized veterinary genetics labs like UC Davis Veterinary Genetics Laboratory, which determines if your dog is Clear, Carrier, or Affected.
• Veterinary Ophthalmic Exam: Performed by a veterinary ophthalmologist, this eye exam at about 6 to 8 weeks of age looks for clinical signs of CEA.

Step 2: Collect the Sample

Your veterinarian can draw a small blood sample from your dog, which is then sent to a reputable lab, most commonly the VGL at UC Davis. This procedure is quick and often occurs during routine health visits.

Step 3: Receive and Understand Results

Results will categorize your dog as Clear, Carrier, or Affected. Clear dogs are safe for breeding relative to CEA. Carriers should be bred carefully, ideally with Clear mates, to prevent affected litters. Affected dogs are generally recommended to be excluded from breeding programs to avoid passing on the disorder.

Step 4: Breed Responsibly

Maintaining genetic diversity is vital. Eliminating all carriers from breeding isn’t advised as it could reduce healthy gene variety. Responsible breeders use test data to avoid carrier/carrier pairings and monitor offspring health diligently, balancing disease control with genetic pool breadth.

Why Testing for CEA/CH Matters

CEA’s symptoms range widely, and even dogs with mild or no signs can pass mutated genes to descendants who may have more severe issues. Testing is crucial to protect breed health and welfare. American breeders and owners of susceptible breeds are strongly urged to test their dogs to preserve strong genelines and reduce blindness risk.

Where to Get CEA Testing in the USA

Authorized genetic testing laboratories include the Veterinary Genetics Laboratory (VGL) at UC Davis, recognized as a leader in genetic screening with breed-specific molecular diagnostics. Your veterinary professional can help arrange sample collection and submission. Private commercial canine DNA services may also offer CEA screening, but for definitive veterinary diagnostics and breeding decisions, VGL is preferred.

Summary and Next Steps

Collie Eye Anomaly is a hereditary eye condition significantly affecting various Collie and herding breeds in the US. Early diagnosis through genetic testing coupled with veterinary ophthalmic exams helps breeders make informed decisions that limit disease incidence and support the health of future dogs.

If you own or plan to breed at-risk breeds, consult your veterinarian for guidance on testing protocols and consider participation in breed health programs that work toward eradicating preventable blindness. Making responsible choices promotes a future with healthier dogs and stronger breed lines.