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>         I got this from the collie club of America site which gave the 2
> year mark for a BCO (Board Certified Opthamalogist) to be able to see it
> during an eye exam....

According to Dr. Kern, an ACVO at Cornell, the form of PRA in Collies,
rod-cone
dysplasia type 2 (rcd2) is almost always detectable by regular CERF exam
MUCH
earlier than 2 years.

As I recall he said that usually if the eyes were easy to read,
something suspicious would probably show up even on an 8-week CERF exam,
and "almost certainly" by 4  months. Regarding "easy to read": I
questioned him about what this meant and again based on sketchy memory,
my impression was that CEA-affected Collies as well as Collies with
light-blue-merle eyes, might have eyes that are hard to read at a young
age, but Collies that do not have CEA and do have regular brown color
(anywhere in the brown range, even if it is lighter than show
preference--for instance, with a yellow ring) are the ones that are
"easy to read".

There are several other forms of PRA found in other breeds, classified
as generalized
PRA, which truly are much much later onset. For these it is possible for
it not
to show up on CERF exam until the dog's prime of life, say 4 or 5 years.
Much
harder to deal with. At least with Collies, one should always be able to
detect PRA by CERF exam prior to breeding age, and thereby at least have
the option of avoiding
breeding from affected dogs. But in Labs, I believe, it is often not
detectable
by age 2, such that a dog CERFs normal, is bred, and a few years later
that dog
may be reCERFed and found to be affected, so every single pup from that
dog is for sure at least a carrier, if not affected.

For several of these breeds, there is now a DNA test that will detect
both
carriers and affected dogs (detectable as soon as one can get a blood
sample,
at birth I guess). That will be a big help to those breeds.

There is also a DNA test for rcd1 which is the Irish Setter PRA. Cornell
has
been working on a DNA test for rcd2 in Collies, but so far nothing
available.

I asked about whether this Collie rcd2 test, when available, would work
in other related
breeds or crosses, if it turned out they also have rcd2 (for example,
Aussie, English
Shepherd or ES/Collie cross) and was told "of course". Dr. Acland
explained how
it works, but I must say I don't really get it.

Gina
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