CORNEAL
DYSTROPHY IN THE BICHON FRISE
By Vickie Halstead RN, CCRN, CEN, CVNS, LNC
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Diagram from The National Eye Institute
http://www.nei.nih.gov/health/eyediagram/
Significance
Bichons are listed as one of the breeds of dogs that are predisposed
to corneal dystrophy. The incidence in the last 3 years from CERF
exams was 39 Bichons, but there must be cases of Bichons that were
diagnosed but not CERF registered. Granted, the incidence is low at
this time, but we need to be aware of this disease before it becomes
more prevalent.
The cornea, the outer transparent portion of the eyeball, consists
of a group of cells and proteins organized into several layers that
must remain transparent to refract light for accurate vision.
Dystrophy is defined as degeneration. This condition is inherited,
non-inflammatory, and tends to be bilateral. The disease is defined
as a condition in which one or more layers of the cornea lose their
normal clarity due to a buildup of cloudy material, thereby
affecting visual acuity.
In addition to opacities in the cornea, alterations in the curvature
of the cornea can bend the light imperfectly into the retina, which
sends an inaccurate image to the brain via the optic nerve. Millions
of humans wear eyeglasses or contact lenses to correct irregularly
shaped corneas, called nearsightedness, farsightedness, or
astigmatism. Corneal dystrophy can affect the curvature of the
cornea by causing swelling in one of the layers of the cornea.
Characteristics
The 3 types of corneal dystrophy are based upon which layer of the
cornea is involved. The major layers of the cornea are:
- Epithelial layer is the outer layer that provides a smooth surface for absorption of oxygen and nutrients from tears, and protects the eye from passage of foreign material.
- Stromal layer is a thick layer (90% of the cornea’s thickness) that consists mostly of water and some collagen that gives the cornea its strength and form.
- Endothelial layer is the very thin innermost layer that is essential in keeping the cornea clear by pumping excess water out of the stromal layer.
Epithelial dystrophy causes painful corneal ulcerations. Endothelial
dystrophy affects the cellular function resulting in edema of the
cornea, which alters its curvature and may cause the eye to appear
blue. Epithelial/stromal dystrophy is evidenced by lipid deposits in
the layers that cause a white or grey opacity. This type of
dystrophy involves a combination of the outer layer and the anterior
portion of the middle layer.
Bichons tend to develop the epithelial/stromal type of corneal
dystrophy, mostly bilateral, at the age of at least 2 years. The
progression is slow and may or may not produce blindness, but the
visual acuity will be diminished as it progresses (cloudy or hazy
vision). This condition is painless unless a corneal ulcer develops,
which is rare with this type of corneal dystrophy.
Treatment
Corneal dystrophies do not respond to topical medications unless a
corneal ulcer is present. The lesions can be removed surgically, but
the opacities can reform and corneal scarring may develop. The best
treatment is prevention by using wise breeding practices.
Breeding Advice
From the CERF data there were 39 cases of epithelial/stromal
dystrophy in the 3 year period from 2001 to 2003. In the 9 year
period from 1991 to 1999, 54 cases of epithelial/stromal dystrophy
were cited and one case of endothelial dystrophy. From this data it
is evident that the prevalence of this disease is increasing in
Bichons. The mode of inheritance for Bichons is unknown at this
time, but for some breeds it seems to be recessive.
Dr. Kirk Gelatt states: “It is important to differentiate corneal
dystrophy (both eyes are eventually affected; no inflammation) from
corneal degeneration (cornea previously injured or ulcerated, and in
the healing process lipids are deposited in the area; usually in one
eye). Also corneal lipidosis may be related to advanced age, high
fat diet, hypothyroidism, and elevated triglycerides/cholesterol in
the blood. There may also be additional unknown factors. Central
corneal lipidosis in a young Bichon that affects both eyes may
signal an inherited disease. The same disease in a 13-year-old dog
may signal systemic disease. The breeder should be guided by the
veterinary ophthalmologist's recommendations.”
Despite the fact that epithelial/stromal corneal dystrophy is
unlikely to produce blindness, the best advice is not to breed
affected Bichons to prevent future increased incidence and severity.
At this time CERF advises “breeders option”, yet other breeds have
reversed this policy due to developing a higher incidence of the
disease with increased severity. Knowing that the age of onset of
this condition in Bichons is at least 2 years, a wise breeder would
not breed a Bichon until the dog is at least 2 years of age to
provide adequate time for genetic diseases to surface. In addition,
this is a reminder of the importance of a yearly CERF exam for
Bichons prior to breeding.
In order to help the BFCA Health Committee understand implications
for Bichons, please report any cases of corneal dystrophy to the
committee at www.bichon.org, with privacy guaranteed.
Research for this article includes the CERF web site and CERF
reports, the textbook Canine Ophthalmology, “Ocular Disorders
Presumed to be Inherited in Purebred Dogs” by the American College
of Veterinary Ophthalmologists, The Merck Veterinary Manual, and The
Dog Owners Veterinary Handbook. This article has been reviewed by
Kirk Gelatt, VMD, Professor of Veterinary Ophthalmology, College of
Veterinary Medicine University of Florida.
Vickie Halstead RN, CVNS, CCRN, CEN has been actively involved in breeding only Bichons
since 1990, producing 20 AKC champions (one is also a CKC champion)
out of 23 litters. She has been a member of BFCA (Bichon Frise Club
of America) since 1997, and has been chair of BFCA’s Health and
Education Committee for 2 years, and is a BFCA Director. Also, she
is a member of ther Bichon Frise Club of Canada. Vickie has been
practicing as a Registered Nurse for 32 years, currently employed as
an ER nurse, and in the past has experience in intensive care and as
a flight nurse. She also has a business involved in independent
teaching of classes for nurses and legal nurse consulting.
Research for this article includes:
The Merck Veterinary Manual
The 5 Minute Veterinary Consult by Larry Tilley& Francis Smith
The Dog Owner’s Home Veterinary Handbook by James Griffen & Liisa
Carlson
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