EYE PROBLEMS
This article is Copyright 1997 by
the Author(s) listed below.
It may be freely distributed on the Internet in its entirety without
alteration provided that this copyright notice is not removed.
It may NOT reside at another website (use links, please) other
than the URL listed above without the permission of the Author(s).
This article may not be sold for profit nor incorporated in other
documents without he Author(s)'s permission and is provided "as is"
without express or implied warranty.
Cindy Tittle Moore,
rpd-info@netcom.com
Copyright 1996.
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.
__________________________________________________________