What
is corneal dystrophy? Corneal
dystrophy is an inherited abnormality that affects one or more layers
of the cornea. Both eyes are usually affected, although not necessarily
symmetrically. Chronic or recurring shallow ulcers may result,
depending on the corneal layers affected:
Epithelial dystrophy causes shallow
painful erosions/ulcerations in the cornea.
With epithelial/stromal dystrophy,
there are whitish crystalline lipid deposits, typically cholesterol, in
the superficial layers of the cornea. This is thought to result from a
disorder of normal lipid metabolism in the cornea. These deposits
usually do not cause problems. You may notice a white to grey opacity
in 1 or both of your dog's eyes.
Endothelial dystrophy affects the
function of the endothelial cells. The result is a build-up of fluid in
the cornea (corneal edema) which clouds the normally
transparent cornea and may decrease vision. Edema may cause the eye to
appear blue. Recurring non-healing shallow corneal ulcers occur as well.
How
is corneal dystrophy inherited? In the Siberian
husky, corneal dystrophy has been shown to be an autosomal recessive
trait, with variable expressivity. In Airedales, inheritance is
sex-linked . The mode of Inheritance in other breeds has not been
identified.
What
breeds are affected by corneal dystrophy?
corneal dystrophy - epithelial
erosion: boxer (7 to 8 years of age and older), Pembroke welsh corgi,
Boston terrier, Shetland sheepdog
epithelial/stromal dystrophy:
Airedale, Afghan hound, American cocker spaniel, Basenji, beagle,
bearded collie, Bichon frise, Briard, Cavalier King Charles spaniel,
dachshund, English springer spaniel, German shepherd, golden retriever,
Irish wolfhound, Labrador retriever, miniature pinscher, Nova Scotia
duck tolling retriever, rough collie, Samoyed, Siberian husky, Vizsla
endothelial dystrophy: Basenji,
Boston terrier, chihuahua, chow chow, dachshund
For many breeds
and many disorders, the studies to determine the mode of inheritance or
the frequency in the breed have not been carried out, or are
inconclusive. We have listed breeds for which there is a consensus
among those investigating in this field and among veterinary
practitioners, that the condition is significant in this breed.
What
does corneal dystrophy mean to your dog & you? corneal dystrophy - epithelial erosion: The
dystrophy that occurs in Shetland sheepdogs occurs as many small
gray-white opacities, which may be associated with painful shallow
erosions of the cornea. In older boxers, dystrophy of the epithelium
causes chronic corneal ulceration. These ulcers are painful and hard to
clear up, and they often recur.
epithelial/stromal dystrophy: The
opacity in your dog's eyes may become quite obvious over time. In most
cases, the accumulation of lipid deposits does not affect vision. In
some breeds such as Airedales (by 3 to 4 years of age) and
beagles, the opacities may progress to the point where they impair
vision.
endothelial dystrophy: Over time,
the fluid build-up causes inflammation of the cornea and reduced
vision. "Water blisters" (bullous keratopathy) may develop which can
rupture and cause painful erosions or ulcers.
How
is corneal dystrophy diagnosed? You or your
veterinarian may notice one or several small white to gray areas in one
or both of your dog's eyes. Magnification may reveal crystalline
deposits within the deeper layers of the cornea or simply a haze.
If there are
epithelial erosions, your dog may show signs of discomfort such as
increased tearing, squinting and rubbing the eye. Your veterinarian
will examine the eye for erosions or, in the case of edema, for bullous
keratopathy. A fluoroscein dye test is used to check for corneal
ulcers.
FOR THE VETERINARIAN: In the
Shetland sheepdog, Schirmer's tear test values are often reduced.
How
is corneal dystrophy treated? For dogs that
experience painful, shallow epithelial erosions (primarily boxers and
Shetland sheepdogs), treatment is aimed at eliminating the lesions.
This will involve medication in the eye. Surgical treatment may be
required if chronic discomfort persists.
Most stromal
dystrophies cause no discomfort and do not interfere with vision. No
treatment is necessary.
In endothelial
dystrophy, no treatment is necessary in the early stages of the
disease. As the edema (or fluid build-up) in the cornea
increases, dogs may develop "water blisters" (bullous
keratopathy) which can rupture and cause painful erosions. Your
veterinarian will prescribe eye medication appropriate for bullous
keratopathy (hyperosmotic solutions) as well as treatment for ulcers if
present. There are surgical treatments which can be performed by a
veterinary ophthalmologist if the erosions persist or recur
frequently despite medical therapy.
Breeding
advice epithelial/stromal
dystrophy: Even though opacities associated with these superficial
corneal dystrophies are rarely dense enough to affect vision, affected
dogs should not be used for breeding.
epithelial
erosions and endothelial dystrophy: Affected dogs and their close
relatives should not be used for breeding.
FOR MORE INFORMATION
ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Where to find more information?
Murphy, C.J. 1992. Disorders of the cornea and sclera. In R..
Kirk and J.D. Bonagura (eds.) Current Veterinary Therapy XI Small
Animal Practice, p. 1101-1111. WB Saunders Co., Toronto.
good information on therapy
reprinted with kind
permission from:-
Alice Crook, DVM,Coordinator, Sir James Dunn Animal
Welfare Centre, Atlantic Veterinary College,University of Prince Edward
Island, 550 University Ave.Charlottetown, PEI C1A 4P3
necessarily
symmetrically. Chronic or recurring shallow ulcers may result,
depending on the corneal layers affected: 
