AOC / CEA: Collie eye anomaly

What is that?
 

Collie Eye Anomaly: AOC or CEA, is an autosomal recessive disease that affects one or both eyes of the dog. This is a developmental defect of the choroid. There is thinning or absence of part of the retina with associated choroidal vascular abnormalities. Many dogs nevertheless have almost normal vision but they may be exposed (5% of affected dogs) to the risk of retinal detachment and retinal hemorrhages which then lead to blindness.

It can be detected between the age of 6 and 8 weeks thanks to an eye fundus for affected dogs, thus making it possible to grade the disease.  A healthy carrier dog will not trace of the disease, this examination is therefore only useful for affected dogs/puppies.

4 grades define this disease, the grade is specific to each individual, grades 1 and 2 are the most frequent (95%), grades 3 and 4 (severe forms) are much rarer (5% of affected)

GRADE 1: choroidal hypoplasia
  On examination of the eye around 7 weeks we will see a depigmented spot as well as an abnormal organization of the vascular network. Once an adult, this anomaly may be invisible on examination, hence the importance of genetic screening .
This grade does not affect the dog's vision and is not upgradeable

GRADE 2: coloboma

  Associated with choroidal hypoplasia, coloboma can affect different areas of the eye (optic nerve, iris, lens). Depending on its size and depth, it may partially impair the dog's vision or not affect it at all.
This rank is not upgradeable

GRADE 3: retinal detachment
Associated with the coloboma of the papilla, it can be partial or complete and leads to irreversible blindness.
This grade is progressive, the dog can become blind after several years or from the age of 3 weeks.

GRADE 4: intraocular hemorrhages
The most severe form but also the rarest, making the animal totally blind irreversibly blind.
This grade can promote the appearance of glaucoma.



Definitions:
Mutated homozygote: -/- which means that the dog is affected and will declare the disease. Grade to be determined on exam
Mutated heterozygote: +/- meaning the dog has 1 allele. He is a Healthy carrier  and does not declare the disease. he can 50% transmit 1 allele to his descendants.
Normal homozygote: +/+ which means that the dog does not carry the mutation, it is said to be Non-carrier, so it does not pass it on to its descendants and will never declare it.

Namely : According to laboratories, 30% of collies are affected in France and more than 50% in the USA.

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Livestock management :

  This is not a rare disease for the American collie, carriers are not withdrawn from breeding among breeders because with screening and breeding selection, high quality dogs can be led to reproduce without generating affected offspring.


You will find a complete file on the Collie Online site dealing with the AOC: www.collie-online.com