Collie Eye Anomaly (CEA): Breeds Affected, Inheritance, and DNA Testing

Collie Eye Anomaly is one of the most prevalent inherited eye diseases in herding breeds. Most affected dogs have mild disease and normal vision — but understanding inheritance is essential for responsible breeding.

CEA (also called Choroidal Hypoplasia) is a complex inherited eye condition affecting the choroid (a layer of blood vessels behind the retina) and in severe cases causing retinal detachment and blindness.

What Is CEA?

CEA encompasses a spectrum of eye abnormalities:

Choroidal Hypoplasia (CH): Underdevelopment of the choroid — the blood vessel layer that nourishes the retina. This is the hallmark of CEA and present in all affected dogs. Most dogs with CH alone have normal or near-normal vision.

Coloboma: A pit or hole in the optic disc or surrounding tissue. More severe than CH alone; vision impact depends on size and location.

Retinal Detachment: The most severe manifestation, causing significant vision loss or blindness. Occurs in a minority of CEA-affected dogs.

Staphyloma: Outpouching of the eye wall. Rare, severe.

Breeds Affected

CEA is most prevalent in:

• Rough Collie (estimated 80-90% of the breed is affected — CEA is near-universal)
• Smooth Collie
• Shetland Sheepdog (Sheltie) (estimated 40-75% affected)
• Border Collie (significant prevalence)
• Australian Shepherd (significant prevalence)
• Boykin Spaniel
• Nova Scotia Duck Tolling Retriever

Inheritance

CEA is caused by a mutation in the NHEJ1 gene and is autosomal recessive:

The severity of disease is variable even among dogs with the same genotype — CEA/CEA dogs range from mild CH with normal vision to severe retinal detachment.

The "Go Normal" Phenomenon

A critical concept for understanding CEA diagnosis: affected puppies may appear normal on ophthalmologic examination after 6-8 weeks of age. This occurs because the abnormal choroid tissue becomes obscured by increasing pigmentation as the puppy matures.

For this reason: CEA evaluation by a veterinary ophthalmologist should be performed at 5-7 weeks of age (before pigmentation masks the lesion). This "puppy eye exam" is when CEA can be reliably detected by clinical examination.

After 8 weeks, clinical diagnosis becomes unreliable — only DNA testing can definitively identify affected and carrier status in older dogs.

DNA Testing

DNA testing for the NHEJ1 mutation is available from Optigen, Embark, Paw Print Genetics, and other laboratories. Cheek swab collection; results identify Clear, Carrier, or Affected status regardless of age.

DNA testing vs. eye exam: DNA testing is definitive and can be performed at any age. Eye examination can identify severity of disease (CH vs. coloboma vs. retinal detachment) that DNA testing cannot distinguish — both are useful tools.

Breeding Implications

Given that CEA is near-universal in Rough Collies (80-90% affected), eliminating it entirely from the breed is not currently feasible without dramatically narrowing an already limited gene pool. The practical approach:

• Test all breeding stock via DNA
• Know carrier and affected status before making breeding decisions
• In severely affected breeds, Carrier × Clear pairings are acceptable (produces no affected offspring)
• Avoid Carrier × Carrier pairings in breeds where Clear dogs are available
• Never breed dogs with severe CEA (retinal detachment) regardless of other qualities

Summary

Collie Eye Anomaly is an autosomal recessive inherited eye condition affecting herding breeds. Most affected dogs have mild choroidal hypoplasia with normal vision; a minority develop retinal detachment. CEA is near-universal in Rough Collies. DNA testing is definitive and should be performed on all breeding stock. The "go normal" phenomenon makes clinical eye examination unreliable after 8 weeks — DNA testing is essential for adult dogs. Carrier × Clear pairings produce no affected offspring.