Corneal Dystrophy In The Bichon Frise

by Vickie Halstead, RN, CVNS, CCRN, CEN, LNC

Diagram from The National Eye Institute
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:

1. 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.
2. 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.
3. 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 using this form, 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