When discussing Collie Eye Problem, there is a general
confusion with using the term "affected".
This word makes it  sound as tho there is something horribly
wrong that will cause the dog to have visual problems or blindness
at some point. In most cases, that is simply not anything
even close to the truth.

"Collie Eye Problem" affects MOST Collies - over eighty percent,
the last time I looked at the figures. The most common type
of "CEP" is something the vets call "CRC" or chorio-retinal-change.  These are cloudy areas discernable only with an ophthalmoscope.
The condition actually disappears to some degree with age - and is sometimes completely indiscernible by the time the puppy is eight weeks old.  This is why reputable breeders have eye checks done before the age of eight weeks - they want to know the true
condition of the eye, not just "get a good eye check" they can advertise.  Many breeders have bred Collies "affected" with
CRC-only for many generations and only rarely - if ever - produce
a puppy with any other CEP related problem.  As dogs with
CRC give every evidence of being able to see every bit as well as dogs with "normal" eyes,  most breeders do not consider it
to be a "problem", or a reason to begin selecting
exclusively from the much smaller gene pool of "normal
eyed" Collies (who may have other genetic or conformational
problems to consider) in  continuing their breeding programs. 

Other problems associated with Collie Eye Problem include
staphlomas and colobomas (which also do not typically cause
discernable visual problems for the dog unless they are
particularly large and in both eyes)  and retinal detachments
(which will cause either partial or total blindness depending
on the degree of the detachment).
Most reputable breeders avoid using dogs affected with these
problems, especially large colobomas or detachments,
in their breeding programs, as they are much more
likely to produce offspring with visual impairment than are
dogs with CRC only.  For the pet Collie, however, the good news
is that even these abnormalities are seldom extensive enough
to actually cause a problem for the dog, or an actual condition
of blindness in one or both eyes. 

All of this is particularly good news for Collie rescuers because,
even tho most of the Collies we see come from less than reputable
breeders,  very few have a degree of CEP that will actually impair
their ability to see, and be a happy pet.

In considering eye problems in Collies, it should also be noted
that Collies may also carry another problem, unrelated to
the Collie Eye Problem.  This is Progressive Retinal Atrophy
or PRA.  There is  currently no gene marker for PRA, and
the only way to have any assurance that a dog is not a carrier
is to check the pedigree and assure that he comes thru all test
bred dogs, or to test breed the dog, or the parents yourself.
Test breeding is a very involved, expensive, and heartrending
process involving the breeding of a PRA blind dog to the dog
you are "testing".  At least seven puppies must result in order
to give 99% assurance (the highest assurance you can possibly get)
that the tested dog is not a "carrier", and they are typically
killed for evaluation purposes.  If they are not killed, testing will
not be complete until after they reach maturity - at which time
some or all may go blind, depending on whether the non-blind parent
is, in fact, a carrier.

One of the famous show winning Collie in the 1970's
who proved to be a PRA carrier was Ch Tartanside The Gladiator.
His offspring was widely test bred, and nearly all of the show
bred dogs coming down from him today are thru dogs who were
test bred and shown to be non carriers.  Many of the other show
dogs who are/were carriers have had owners or breeders who
were not so public about their "problem", have not done any test
breeding, but have continued to produce generations of Collies
from affected dogs.  Being that the anomaly is carried recessively,
it may not express for a number of generations, and then
"suddenly" PRA blind dogs will appear.  Sadly, there are many
such pedigrees around today - and those knowledgeable about
them are typically sought out for advice when one is considering
an outcross from a  reliably "test bred" line.  To make the
proverbial water even muddier, many of the dogs who are
"normal eyed" and "non carriers" for CEP, are carrying PRA.
Unfortunately, many of the breeders working with these lines
are fairly new to the Collie world, and have been erroneously told
by others that "As long as there's no Ch Tartanside The Gladiator
behind your dogs, you won't have PRA".  This, of course, is not
only the opposite of the truth, but  an absurd indication of why
breeders who have genetic problems show up in their dogs are
fearful of being "public" about it.  The one dog who's
breeder / owner vas VERY open about this problem,
and who worked hard to be sure that his offspring were all tested
and the carriers eliminated from the breeding program, is the
dog that, thirty years later, is being erroneously maligned by
those who simply "heard the name" in connection with PRA,
and don't realize that they are probably working with carrier
lines, while the one line they are degrading is actually clear.
PRA is still very much with us, and certainly more than one dog
who is  "normal eyed" or a "normal eyed non carrier" for CEA
has gone blind from PRA, or produced PRA blind or carrier
puppies.  Unlike CEA, which seldom causes blindness,
PRA will always cause the dog to eventually go blind, and
go blind in both eyes, and should therefore be heavily
considered when choosing a line, or a Collie for breeding.


Terry Thistlethwaite
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