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16 Eye Problems




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This article is from the Canine Medical Information FAQ, by Cindy Tittle Moore with numerous contributions by others.

16 Eye Problems

Following are short synopses of the most common forms of eye problems. CEACEA
(Collie Eye Anomaly) is the most common form of eye problem found in the
collie, both rough and smooth variety. It is also found in the border collie,
shetland sheepdog, and bearded collie. It is believed to by controlled by a
genetic cluster, or large group of genes, and thus, it is hard to control by
breeding, and ranges in severity. PRAPRA (Progressive Retinal Atrophy) is
common in MANY breeds of dogs (including mixed breeds), and is not isolated
to the collie like the CEA tends to be.

PRA affects the entire retina and is the canine equivalent of retinitis
pigmentosa. This disease manifests itself differently in different breeds.
The most common form of PRA in the collie is detectable at early age (6wks
and over). The form of PRA in Irish Setters is also early-onset. In Labrador
Retrievers, on the other hand, the age of onset is much later, typically four
to six years of age, making it much harder to find and isolate carriers in
this breed.

PRA has been detected as early as six weeks in puppies, and these puppies are
usually blind by six to eight months. An electroretinography can be used to
detect the early signs of PRA. Animals to be tested in this manner are
anesthetized while lenses are placed on the eyes to record the retina's
reaction to light. (Like wearing contacts.) In other cases, ophthalmological
examination by ACVO-certified vets can pick up cases of PRA and confirm them
with electroretinography if desired.

All dogs affected with PRA eventually go blind. Carriers show no clinical
symptoms. Symptoms are subtle, starting with night blindness, some eye
dilation, to progressive blindness. It's quite common to not notice anything
is wrong until the dog is nearly completely blind. Proactive testing is
always recommended, especially for breeding stock.

Current research is beginning to isolate the genetic markers for this
disease. At present, there is a genetic test to identify carrier and affected
dogs in the Irish Setter breed. Work is underway for one for the Labrador
Retriever. This disease is thought to be a simple autosomal recessive gene.
Thus two recessive genes are needed for a dog to be affected. A single
recessive gene masked by the healthy dominant means the dog is a carrier.
Therefore, an affected dog's parents are carriers or also affected.

NOTE: In October 1945 the Kennel Club of England added PRA to the list of
disqualifications from winning any award in the show ring. GlaucomaThis is a
condition where the pressure of the fluid in the eye increases until the
sight is gone in that eye. If it strikes one eye, the other eye is likely
also to be affected. Glaucoma is one of the leading causes of blindness in
dogs. Any underlying problem that increases the fluid pressure inside the eye
is the culprit; most of the time this is due to inadequate drainage of fluid
from the eye (as opposed to overproduction of fluid). A few forms of glaucoma
are thought to be hereditary.

Signs of glaucoma include reddened conjunctival tissue (red eye), weeping,
light sensitivity, or even enlargement of the eye. As pressure increases, the
pupil can become dilated and the cornea cloudy. Early diagnosis is critical
to save the vision of the dog, and involves treating the underlying causes of
the increased pressure if at all possible.

Once the retina is damaged and the sight is gone the options are as follows:
* Inject the eye with a fluid which kills the fluid producing cells
in the eye, hence no further increase in pressure and no pain.
This is not a guaranteed solution.
* Diode laser cyclophotoablation
* Remove the eye and sew the lids shut. Probably the most practical.
* Remove the eye and replace it with a prosthetic (i.e., glass eye).
There are potential problems with infection of the eye socket.

CataractsCataracts are relatively common in dogs and most are hereditary. An
ACVO-certified veterinarian can easily detect these cataracts. Haziness or
cloudiness in the eyes in older animals is often _not_ cataracts. Hereditary
cataracts can be found in many breeds of dogs and can be detected early in
age, so all breeding stock should be screened for cataracts before being
bred.

Cataracts may be stable or progressive. In the former case, owners may never
be aware that their dog has cataracts until or unless the dog is examined. In
the latter case, the dog often adapts very well to the gradual loss in vision
until a certain point is reached. General diagnosis can be done by
ophthalmoscopic examination; if a more detailed examination is needed, a slit
lamp examination must be performed.

Surgery is the only option for cataracts that seriously impair vision. Most
surgery involves removal of the lens; however, implants can also be
performed. Recovery and prognosis for these dogs are generally good. Retinal
Dysplasia There are several types of Retinal Dysplasia:

Retinal Dysplasia-complete
Relatively rare, puppies are blind from birth and appears to be
a simple autosomal recessive. Mostly reported in Europe. No
skeletal abnormalities are associated with this form of RD.

Retinal Dysplasia-folds
This form of RD is called "retinal and vitreal dysplasia with
skeletal abnormalities" or "dwarfism with retinal dysplasia".
In this disease, three different ocular phenotypes are present
(normal, localized retinal dysplasia (retinal folds), and
complete retinal detachment) and two different skeletal
phenotypes are present (normal or dwarf). This is an inherited
condition, whose mode of transmission is as follows: Call N the
normal gene and rd the gene for retinal dysplasia.

+ N x N normal eyes, normal skeleton
+ N x rd classic symptoms, retinal folds, normal skeleton
+ rd x rd dwarfism, eye problems/blindness, skeletal problems

The gene acts as an autosomal recessive in regards to dwarfism,
but acts as though it were dominant when only one parent passes
on the gene to its offspring.

If we bred NN x Nrd we would expect half of the puppies to be
affected the others normal. If we bred Nrd x Nrd we would
expect the following:

+ 1/4 normal
+ 1/2 afflicted carriers, can be identified in puppies
+ 1/4 dwarf

that the ocular and skeletal defects are inherited together,
and that the skeletal effects act as a recessive trait and the
ocular effects act as an incomplete dominant trait. This
implies that 1) any Labrador with any type of RD is a carrier
for dwarfism, and 2) at least one of the two parents of puppies
with RD is a carrier for dwarfism. Retinal folds _may disappear
with age_, so an accurate evaluation for RD requires that
puppies be evaluated, ideally between 8 and 10 weeks of age.

In mild cases of retinal dysplasia, sight is probably not
affected much, if at all. In severe cases, skeletal
abnormalities are present.

Dealing with Blindness

Dogs that become blind rarely have all that much trouble with
it. Unlike humans, sight is not a primary sense; dogs would be
much more upset at losing their sense of smell. Most people
with a blind dog find that dealing with blindness is not
difficult nor traumatic for the dog.

To avoid confusion, do not move your furniture around (except
for any piece that the dog does keep bumping into. Be sure the
dog knows when you are near so it is not startled. When you go
out on walks, establish habitual trails. Your dog will adjust
quickly.

References

For more information on Canine Eye disease contact:

CERF (Canine Eye Registration Foundation)
South Campus Courts C, Purdue University, West Lafayette, IN 47906

Vanderlip, Sharon Lynn, DVM. _The Collie: A Veterinary
Reference for the Professional Breeder_.

Dr. Lionel Rubin, V.M.D., U of PA Vet Sch on Retinal Dysplasia.

Carrig, Sponenberg, Schmidt, Tvedten, JAVMA, Nov 1988.

Oliivero, DVM, Retriever Field Trial News, June 1993.

Rubin, Lionel F. _Inherited Eye Diseases in Purebred Dogs_,
Williams & Wilkins, Baltimore, 1989.

CERF Publication "Ocular Disorders Proven or Suspected to be
Hereditary in Dogs". The publication can be ordered directly
from CERF by calling their office at (317) 494-8179.

Barnett, KC, et al: Hereditary retinal dysplasia in the
Labrador Retriever in England and Sweden. J of Small An Prac,
10:755, 1970.

Carrig, CB, et al: Retinal dysplasia associated with skeletal
abnormalities in Labrador Retrievers. JAVMA, 170:49, 1974.

Carrig, CB, et al: Inheritance of associated ocular and
skeletal dysplasia in Labrador Retrievers. JAVMA, 193:1269,
1988.

Neslon, B, MacMillan, A.: Multifocal retinal dysplasia in the
field trial Labrador Retriever. JAAHA, 19:388, 1983.

 

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