COLLIE EYE ANOMALY
This is the most
common of the Collie eye diseases, but it
should be noted that Collies share this
disease with several other breeds.
Researchers first noted this problem nearly
fifty years ago. It was later found to exist
in most Collies and in most Collie families.
This so-called syndrome, meaning a group of
conditions which appear in conjunction with
each other, is present prior to birth.
Collie Eye Anomaly can be easily
checked when the puppies are 5-6 weeks old,
by a qualified Board Certified
Ophthalmologist. It is something that your
average Veterinarian is not qualified to
diagnose. The eyes must be dilated prior to
the examination, so the interior of the eye
can be examined with an Ophthalmoloscope.
A dog is either
given a “Normal” or "Affected" rating. If
given "affected" the type of abnormality is
noted. It used to be popular to use a
Grading System and still is being used in
certain parts of the country. Currently
there is no universal, standardized grading
system.
Normal:
A “Normal”
eye rating is of course the best grading
there is. (There are also "Go Normals",
which are so mildly affected at a young age,
that later, the pale areas disappear,
leading to what is termed a "Go Normal".
Keep in mind that these are still in fact
affected with CEA). There are variations
even in "Normal" eyes. These
correspond somewhat to a dog's coat color.
Thus it is often difficult to judge the
pigment in a Blue Merle's eyes as it is
diluted along with his coat color.
Choroidal
Hypoplasia, Chorioretinal Change:
These
refer to abnormalities in the coloring or
pigmentation of the choroid or central layer
of the eye's lining. This is the most common
abnormality found in Collie eyes. Often
referred to as mild CRC, Grade I or Grade
II, it is the least harmful and least severe
form of CEA. Most dogs with this eye grade
function normally with no ill-effects or
loss of vision.
Staphyloma, Coloboma, Ectasia:
While not completely synonymous, these terms
all refer to a cupping or bulging in the
eyeball usually in the area of the optic
disc.
Vascular Disease, Tortuous Blood
Vessels:Defects
in the vessels of the eye which are
responsible for its blood supply or
"nourishment." These may be malformed,
undersized, or even lacking.
Retinal Detachment:
Loosening or separation of the inmost, or
retina, layer from the wall of the eye. This
may involve a tiny area or the entire
retina. It can be either one or both eyes.
The complete detachment of the retina
results in blindness in that eye.
There is a new
Genetic Test for Collie Eye Anomaly /
Choroidal Hypoplasia. Please visit the
OPTIGEN website for details
Can the Collie's eyes become worse? Might he
later go blind?
The basic answer is "No" as CEA is present
prior to birth. However, a dog born with a
severe Staphyloma or with Vascular Disease
may later suffer loss of sight if a
detachment or severe hemorrhage occurs. The
majority of dogs that are slightly affected,
will have perfectly adequate eye vision
throughout their life. (Even a dog with one
blind eye will adapt perfectly well in his
surroundings.)
What have
breeders done to improve Collie eyes?
When the eye problem was discovered more
than 50 years ago, it was estimated that 90%
of the Collie population was afflicted with
some form of eye disease. Because CEA has
involved such a large percentage of the
breed, eradication has been slow . Over the
years, with selective breeding and eye
checking of breeding stock, the numbers of
affected Collies has greatly reduced. ALL
reputable breeders eye check not only their
breeding stock, but all puppies that are
offered for sale.
How is CEA
inherited?
Most of the specialists agree that Choroidal
Hypoplasia is carried as a simple recessive.
For a dog to show symptoms, both
parents, even if they show no signs
themselves, must carry a gene for the
condition. Evidence exists that some other
parts of the syndrome are inherited
differently. Staphyloma, for instance,
rarely occurs except in the presence of
Choroidal Hypoplasia. Dogs recommended for
breeding will vary according to the standard
set by the individual doctor. The ideal, of
course, is to eliminate all but the clear,
non-carriers, from the breed. Please note:
Even among the dogs that examine "normal",
most are carriers of the gene. They have a
"hidden" or recessive gene for the condition
and will transmit the gene to half its
offspring.
Two other conditions
not part of the CEA, which can occur, should
be noted:
Hypoplasia of the Optic Nerve:
An undersized nerve which is noted where it
enters the eyeball. In extreme cases, this
can cause blindness.
Corneal Dystrophy:This
condition comes on when the dog is mature,
often during stress. Opaque spots appear
centrally on the surface of the cornea. (It
is often confused by the layman with
cataracts which occur in the lense.)
In the beginning there was a lack of
veterinarians trained to examine eyes. Then
in 1972, the American Veterinary Medical
Association formed the American College of
Veterinary Ophthalmologists (ACVO), thus
providing specialists in the animal eye
field. The Collie Club of America encourages
its members to have all their puppies
checked as young as possible by a member of
the ACVO. Where there is none in the area,
the alternative is to sell a dog contingent
on a later check. No dog should be used for
breeding until examined and found to be
above the examiner's standard.
PROGRESSIVE RETINAL ATROPHY
The other Collie eye
problem that can occur in rare instances is
Progressive Retinal Atrophy (PRA).
Since the name is just what it implies, it
can be a progressive disease, that may not
appear until later in life. This is a
completely different and unrelated disease
to CEA. As the name indicates, PRA is a
progressive disease which refers to retinal
degeneration. It can result in complete
blindness in one or both eyes. However,
Collies seem to be blessed with the fact
that PRA seems to have an early onset.
Fortunately, this is an eye disease that has
largely been eradicated thanks to breeders
efforts of test breeding potential carriers.
Since PRA is a simple recessive gene, it is
much easier to test for than CEA. Also,
thanks to funding of certain grants by the
Collie Health Foundation, research is being
done to locate the genetic markers for this
disease, which will further reduce the
occurrence. Currently there is no genetic
test for PRA, but rumor is that researchers
are very close to finding a DNA marker.
PRA has proven to be
a simple recessive in all the breeds
studied. Again, this means that even though
the condition is not present at birth,
both parents must be carriers. If
one parent has PRA, half the puppies may
develop PRA, but all will be carriers for
the disease. Early signs of the problem may
be noticed by the owner as "night
blindness." The dog has trouble seeing in
dim light and will bump things. An expert
may detect early signs in the eye at six
months or younger
