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 knowledgeable 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" eye checks,  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 knowledgeable 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 those involved with Collie rescue because, even though most of the Collies who go through
rescue groups come from unknown breeding, 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.  For many years, the only way to have any assurance that
a dog was not a carrier of PRA was to check the pedigree and 
assure that he came thru all test bred dogs, or to test breed the 
dog, or the parents yourself.

Test breeding was a very involved, expensive, and heartrending
process involving the breeding of a PRA blind dog to the dog
you were "testing".  If  fewer than seven puppies resulted in the
litter, the breeding would have to be repeated to obtain enough
individuals to make the test reliable.  As PRA is not evident before
maturity, those puppies had to be maintained and grown out
until adulthood.  At that time some or all may have gone blind, depending on whether the  non-blind parent was, in fact, a carrier.

Those who undertook the formidable task of PRA  test breeding 
over a course of several decades provided an invaluable service
to the Collie breed as a whole which arguably kept it from being 
destroyed by an otherwise undetectable gene.

One of the famous show winning Collies 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.  Thanks to these concerted
efforts, we have many families of PRA clear Collies today coming
down from that beautiful dog.   

While there are still some pedigrees around today from which the
PRA gene has not been cleared, we have enough test bred lines
to be able to make responsible choices in breeding stock. It is nonetheless important to understand, however, that many
of the dogs who are "normal eyed" and "non carriers" for CEP 
may still be carrying PRA -- as these terms typically refer only
to the Collie Eye problem. 

The Collie has been blessed with generations of dedicated
breeders working diligently to preserve and promote the breed
for the enjoyment of new fanciers and breeders to come.  
Collie Eye Problem is, for the most part, a mild imperfection 
causing no visual impairment whatsoever and is certainly well under
control.  PRA, still present in some lines and families, has been
eradicated from many lines and breeders are still working to see
it disappear completely.  Anyone considering the purchase of
a Collie puppy today has every reason to expect they can easily
find a beautiful and healthy puppy who will enjoy a lifetime of
good vision.

Understanding Collie Eye Problem
by Terry Thistlethwaite
You're listening to 
"Irish Eyes"
(Irish folk song)
Tartanside Integrity
Chekia Delicious
Chekia Littlefield Lassey
Star Country From The Heart
  Dr. Richard Donovan DVM, board certified veterinary ophthalmologist
  founder of The Retina Foundation, Boston, Massachusetts.
  Dr. Donovan initiated studies on CEP which included test breeding programs and afforded the Collie breeder 
  community with all of the original pertinent data on the individual and generational affects of CEP.  
  It was Dr. Donovan's willingness and determination to work with Collie breeders in addressing the initial concerns 
  over CEP that brought about the development of  the "grade" eye check system instrumental in preserving the breed.