About 95% of collies have some form of CEA. This eye exam can only
be given by a Certified Canine Ophthalmologist. CEA or Collie Eye Anomaly is thought to be inherited by an
autosomal recessive gene.
A recessive trait means there are three types of dogs: unaffected
dogs that do not display the trait NOR have genes for the trait; carriers that do not display the trait, but DO have one of
the genes for the trait; and affected dogs that have the trait and can only pass along genes for the trait. If a dog is "mildly
affected", it is an affected dog and will always pass along CEA to it's puppies. So breeding two "mildly affected" dogs will
never result in unaffected, or even carrier puppies. Breeding two apparently normal dogs may result in puppies with CEA if
both dogs turn out to be carriers. If a dog ever produces a puppy with CEA, then that dog must be either a carrier or an affected
dog itself.
An affected dog is one who, upon dilation of the eye, shows a visible deviation
from a normal or unaffected eye when viewed with the proper instruments. To be affected a dog would have inherited an
affected gene from both parents.
A normal eyed dog is a dog
who, when examined by a veterinary ophthalmologist shows no visible signs of CEA, but possesses only one normal gene; the
other gene is affected.
A non-carrier is a normal eyed collie who carries no affected genes. He cannot
produce anything but normal eyed collies
A non-carrier cannot be
diagnosed by an eye check, as we are dealing with genes not effects of genes. If a dog comes from two non-carrier parents,
he is a non-carrier. Whether or not a dog is a non-carrier can only be defined by breeding. If a dog produces a significant
number of puppies, bred to an affected or normal eyed stud or bitch, and all have normal eyes, no matter what the eye check
of the other parent is, it's a safe bet he/she is a non-carrier.
Progressive Retinal Atrophy
PRA will result in blindness. A well known and widely used stud dog in the '70s was found to
be a carrier and did produce blind puppies. While the breeder now test-breeds all their stock available for stud services,
PRA is present in a number of lines. Most reputable breeders who know or suspect that PRA is in their lines do test-breed.
Since PRA in Collies is a simple recessive, it has been easier to control than CEA.
ALL reputable breeders should eye check not
only their breeding stock, but all
puppies that are offered for sale.
