Corneal dystrophy

What is ... ?: 

 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 ... 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 does ... 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 ... 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.  
 

How is ... 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.
 

For the veterinarian: 

 In the Shetland sheepdog, Schirmer's tear test values are often reduced.

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.
 

Resources: 

 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


What breeds are affected by ... ?
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