Collie Eye Anomaly

Collie eye anomaly (CEA) is an inherited congenital condition affecting the development of the eye. It primarily affects the choroid — the vascular layer beneath the retina — resulting in an area of choroidal hypoplasia (underdevelopment) in a characteristic location lateral or dorsolateral to the optic disc. The condition is present from birth and affects both eyes, though the two eyes may be quite dissimilar in the extent of the changes.

CEA encompasses a spectrum of severity. In its mildest form, only choroidal hypoplasia is present and vision is unaffected. In more severe cases, colobomata (developmental defects, typically at or near the optic disc) are present in addition to choroidal hypoplasia. Retinal detachment and intraocular haemorrhage, the most serious complications, are fortunately rare.

The "go normal" phenomenon

One of the most clinically important features of CEA is the so-called "go normal" phenomenon. In young puppies, the choroidal hypoplasia lesion is clearly visible as a pale patch in the fundus. However, as the puppy develops, the normal maturation of retinal pigment and the tapetum can partially or completely obscure the hypoplastic area, making the fundus appear normal on ophthalmoscopic examination in the adult dog.

This means that a dog which appears clear on adult examination may in fact be genetically affected. Studies in Rough Collies in Norway have shown that as many as 68% of puppies confirmed as having mild CEA at 7 to 12 weeks of age had a fundus of apparently normal appearance when re-examined at around one year of age.

This is why litter screening between 5 and 7 weeks of age is the most reliable method of clinical diagnosis, and why DNA testing is particularly valuable in this condition - it identifies affected and carrier dogs regardless of age or the "go normal" effect.

Breeds affected

CEA is certified under the BVA scheme in the Border Collie, Rough Collie, Smooth Collie, Lancashire Heeler, and Shetland Sheepdog. Ophthalmoscopically identical lesions have been described in several other breeds including the Australian Shepherd and Nova Scotia Duck Tolling Retriever, though the genetic basis may differ.

DNA testing

A DNA test is available for CEA, targeting the mutation responsible for choroidal hypoplasia. The test can identify clear, carrier, and affected dogs at any age, making it a valuable complement to litter screening — particularly for identifying carriers who show no clinical signs. Even with a DNA test, ophthalmoscopic litter screening remains important for detecting colobomata, which may be caused by a related but distinct genetic variant.

What the examination involves

Litter screening for CEA is performed in puppies between 5 and 12 weeks of age, ideally between 5 and 7 weeks for maximum diagnostic accuracy. All puppies must be microchipped before examination. The examination is performed following pupil dilation and is well tolerated by young puppies.

Litter screening is available at all our regular clinic dates. Please mention at the time of booking that you are bringing a litter for CEA screening, and let us know how many puppies you are bringing. The first puppy is examined at the standard BVA litter screening fee; additional puppies are invoiced on the day at the BVA additional puppy rate.