New Progressive Retinal Bro
TREATMENT
Unfortunately, no effective treatment has been
formulated to prevent, treat, or cure progressive
retinal atrophy. As stated previously, affected ani-
mals should be identified as early as possible and
eliminated from breeding programs.
PRA
MANAGEMENT OF PETS WITH POOR VISION
Progressive retinal atrophy is a painless condition.
Pets that lose sight as a consequence of PRA usually
adjust well to their environment with time.
Progressive
Maintaining a consistent environment for the affect-
ed animals will help this process. Frequent furniture
Retinal
rearrangement during this period should be avoided.
Owners with backyard pools need to be especially
Atrophy
watchful, since even a proficient swimmer may be
unable to find the steps out of a pool. When animals
are taken from their home environment, use of a har-
ness and leads are helpful. Continued affection and
encouragement by their owner will comfort an
affected animal. The exceptional senses of smell and
hearing in animals also help pets adapt to vision loss.
RETINAL ATROPHY IN CATS
Progressive retinal atrophy also occurs in cats.
PRA is occasionally seen in the Abyssinian and
Siamese breeds in Europe and in North America.
Cats that have a diet deficient of the amino acid
Taurine develop a condition similar to progressive
retinal atrophy. Taurine is found in many animal
products and meats, but is not present in veg-
etable matter. Most commercial cat foods provide
adequate levels of Taurine.
CONCLUSION
Progressive retinal atrophy refers to a broad cate-
American
gory of inherited retinal diseases that result in
blindness in dogs and cats. Because of the insid-
The ACVO is continually involved in basic and clinical
ious nature of the disease and in some breeds, the
research developing new diagnostic procedures and treatment
College of
late onset, several examinations may be required
regimens. The genetics committee of the ACVO works closely
with breeders to better define and help eliminate inherited ocu-
to detect affected individuals. Individuals affect-
lar diseases.
ed should not be used for breeding, and pedigree
Veterinary
studies are indicated to eliminate other potential
The name of a diplomate closest to you may be obtained from
carriers for these diseases.
a general practitioner in your area, by contacting your local or
Ophthalmologists
state veterinary medical association, the AVMA, or on-line at:
www.acvo.com.
Understanding PRA
in the pet's normal environment occurs, such as when
“In many animals, PRA progresses
furniture is rearranged in the home or when the animal
slowly and early signs may be over-
is taken into an unfamiliar area. Since PRA can be dif-
ficult to identify, routine ophthalmic examinations of
looked.”
Retina
all pets is recommended. This is especially important
Cornea
in animals that are being considered for breeding.
CLASSIFICATIONS
Lens
Most retinal atrophies are inherited, although rare cases
“Often vision loss is not noticed until a change in the
of nutritional based retinal atrophy have been described.
pet's normal environment occurs.”
Recently, veterinary ophthalmologists have observed an
atrophy associated with changes in appetite and water
DIAGNOSIS
consumption in patients. This disease, known as sudden
acquired retinal degeneration (SARD), is not considered
When an ophthalmologist uses an instrument to view
to be inherited and affects purebred as well as mixed-
the retina, changes
breed dogs.
are frequently seen
in the eye which
INTRODUCTION
usually allow for
CLINICAL SIGNS OF PRA
To better understand progressive retinal atrophy, one must
early detection of
have a basic understanding of the function of the retina.
The early signs of retinal atrophy include night blind-
retinal disease.
The retina is a highly specialized sheet of neurological tis-
ness, which usually progresses to day blindness. Pupils
Certain breed char-
sue located at the back of eye. The retina is similar to film
may be dilated and have a slow response to light. Some
acteristics make it
in a camera; it is located in the rear portion of the eye and
pet owners notice a characteristic shine from the eye.
difficult to detect
it is responsible for integrating light into vision. Without
Night blindness may manifest in a number of ways,
early changes, and
a normally functioning retina, vision is not possible.
including a fear to go outside in the dark or into a dark
may appear nor-
room. Pets may get lost in their own home after the
mal until the dis-
Simplified, the eye can be thought of as a light-collecting
lights have been turned off.
ease has pro-
organ that focuses light rays on the retina. As light strikes
gressed.
the retina, a sequence of chemical reactions is initiated
As previously mentioned, retinal abnormalities may not
Fig. 3: Electroretinogram being performed.
and results in an electrical impulse. The impulse passes
be noticed at home until later in the course of the dis-
Cataracts may
through the layers of the retina to the optic nerve, and
ease. Other well-developed senses including the senses
form following the development of progressive retinal
finally to the visual cortex in the brain for interpretation.
of smell and hearing help animals adapt to the slow loss
atrophy in some animals. The formation of cataracts may
This broadcast of a signal created by the retina and analy-
of sight. Often vision loss is not noticed until a change
interfere with the direct opthalmoscopic evaluation of the
sis by the brain are required for normal vision.
retina, this mandating the use of other diagnostic tech-
niques for the establishment of a definitive diagnosis.
As the name implies, an atrophy or a degeneration of retinal
tissue occurs in this disease. In many animals, PRA pro-
gresses slowly and early signs may be overlooked. The
ELECTRORETINOGRAPHY
gradual loss of sight is similar to the effects of a dimmer
Definitive diagnosis of PRA can be confirmed by elec-
switch used to reduce brightness in a room. If the light is
troretinography. This non-invasive test involves the use
slowly reduced, our eyes concurrently adapt and the change
of sophisticated instrumentation to measure electrical
is not noticed until near total darkness occurs.
impulses within the retina. It is similar to an electrocar-
Unfortunately, there are no cures available for progressive
diogram for the heart, in that they both measure electri-
retinal atrophy. Identification of affected animals used in
cal impulses and produce characteristic, recordable
breeding is essential to prevent spread of the condition with-
wave forms. After a period of dark adaptation, a light is
in the breed. Pets diagnosed with PRA should not be bred.
used to stimulate the retina. A healthy retina produces a
characteristic recording. This instrument is sensitive
enough to diagnose affected dogs before they begin to
demonstrate clinical signs.
Fig. 2: Indirect ophthalmoscope examination.
