RETINAL
FOLDS AND RETINAL DYSPLASIA
By Vickie Halstead, RN, CVNS, CCRN, CEN
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Diagram from The National Eye Institute
http://www.nei.nih.gov/health/eyediagram/
ETIOLOGY
Retinal folds and retinal dysplasia are closely related eye diseases
that are primarily inherited, suspected to be autosomal recessive.
Other causes include toxicity and infections during pregnancy,
including herpesvirus and possibly parvovirus. These diseases are
found in bichons, although not frequent among our breed compared to
some other breeds. CERF reports for the last 12 years cite 43 cases
in bichons, but this does not account for the majority of bichons
who do not undergo annual CERF examination. Because these diseases
may cause blindness in puppies, bichon breeders need to be aware
that we should not be breeding affected bichons, and of course we
should all CERF our breeding stock.
PATHOPHYSIOLOGY
The retina is a layer of sensory tissue that is attached to the
tissue in the back of the eye. The retina receives light stimuli
from the environment and converts it to an electric signal that is
sent to the brain via the optic nerve, which lies behind the retina.
The brain interprets this signal and vision occurs. Any alterations
in the retinal tissue can impair vision. The retinal tissue
undergoes changes until the eye is fully developed at the age of one
year.
Dysplasia is defined as abnormal growth or development. Retinal
dysplasia forms when the 2 developmental layers of the retina do not
unite properly. It can involve both eyes or one, but the inherited
form is almost always bilateral. It can occur anytime during eye
development, from pregnancy to one year of age. There are 3 forms of
retinal dysplasia:
- Focal retinal folds: These are wrinkles in the retinal tissue in
one or more areas. They cause small blind spots, but rarely cause
visual impairment for the dog. They primarily occur in young dogs
with developing retinas, and usually disappear by the age of one
year. Young dogs (<1 year of age) with folds only are not at risk of
developing dysplasia at a later age.
- Geographic retinal dysplasia: This consists of irregularly shaped
areas of the retinal tissue that appear like a rosette upon
examination. This may cause some degree of visual impairment and
possibly blindness. This can develop at anytime up to one year of
age and is usually permanent. In puppies, this can co-exist with
folds since folds and dysplasia are difficult to differentiate in
the immature retina. As the folds disappear later when the retinas
mature, the dysplasia will persist.
- Generalized or complete retinal dysplasia: This form exhibits
severe retinal disorganization and is associated with detachment of
the retina. Detachment occurs when the retinal sensory tissue
separates from the tissue in the back of the eye, thereby causing
complete blindness. This is detectable at birth and is permanent.
PROGRESSION
Retinal dysplasia is not a progressive disease, but it will continue
to develop until the retinas are mature at around one year of age.
To allow the retinas time to mature, the earliest age for a CERF
screening for this disease is 6 months, yet closer to one year is
recommended by Dr. Kirk Gelatt at which time a definite diagnosis
can be established. If you suspect one of your puppies has visual
impairment, seek an ophthalmology exam immediately. Signs would
include frequently bumping into objects, less activity, and possibly
timid or fearful.
MANAGEMENT
There is no treatment for this disease. The best we can do is to
strive to prevent it. The literature recommends that dogs affected
with either of the 2 more serious forms of dysplasia (geographic or
complete) should not be bred, as well as their parents and their
littermates. The genetic relationship between retinal folds and the
other 2 forms of dysplasia is unknown at this time. Some
ophthalmologists suggest that a mature dog with persistent retinal
folds may produce more severe forms of the disease in their
offspring, secondary to the dog being a carrier of the gene for the
more severe forms of dysplasia. What appear to be folds on exam can
sometimes be dysplasia, so a mature dog with folds or dysplasia
should not pass a CERF exam. In addition, one may wonder if retinal
dysplasia could play a role in the incidence of retinal detachments
that occur after bichon cataract surgery. According to Dr. Kirk
Gelatt, post-operative detachments are primarily related to
“cataract maturity and the secondary lens-induced inflammation,
rather than retinal dysplasia”.
ADVICE FOR BREEDERS
As responsible bichon frise breeders, we need to be aware of retinal
dysplasia and stop the progression of this disease in our breed
while the incidence is low. We can accomplish this by completing the
initial CERF exam near the age of one year and not breeding bichons
with persistent retinal folds or retinal dysplasia. In the past,
some bichon breeders were advised that there is no reason to CERF
until the age of 2 years, since the age of onset of the bichon
cataract is 1.5-2years. Dr. Gelatt feels that although this disease
is limited in bichons and seldom impairs vision, an affected bichon
and its parents should not be used for breeding. He also states
“There is no reason to CERF before six months to one year unless you
suspect vision problems.” Besides, knowing that your bichon has
retinal dysplasia would be beneficial before spending the time and
money to complete its championship.
Since the Health and Education Committee feels that this disease
deserves vigilance, we will keep you informed on recommendations for
screening for retinal folds and dysplasia. We also encourage you to
share data with our committee, which will remain confidential, so
that we can be aware of current trends in health problems in bichons.
Research for this article includes The Merck Veterinary Manual,
The Dog Owners Veterinary Handbook
plus numerous medical and veterinary sources
Article reviewed for accuracy by Kirk Gelatt, VMD
Professor of Veterinary Ophthalmology
College of Veterinary Medicine
University of Florida
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