Among the many inherited conditions that can affect your dog's eyes are a group known as corneal dystrophies. These conditions cause abnormal corneal development, usually in both eyes, and lead to various problems with the animal's vision. Depending upon the type, one or more layers of the cornea (the transparent lens that covers the front of the eye) will be affected. The major types of corneal dystrophies are: Epithelial Dystrophy, which causes shallow but painful ulcers and erosion on the surface of the cornea. Endothelial Dystrophy, which affects the function of the endothelial cells, causing a buildup of fluid in the cornea (also known as corneal edema). Since the cornea is normally transparent, this fluid causes cloudiness and can impair the dog's vision. Corneal edema often causes the dog's eyes to appear bluish, and these animals also may develop chronic ulcers on the cornea that are slow to heal. Epithelial/Stromal Dystrophy causes whitish crystalline deposits of cholesterol to form in the outer layers of the cornea. It's believed to be caused by metabolic malfunctions within the cornea itself. Some pet owners will notice their dog's eyes have a whitish or grayish tint, but the dog's vision is not usually affected. It's not known what causes corneal dystrophies in most animals; therefore it's recommended that affected animals and their siblings not be bred. Research has shown that they are transmitted through a recessive gene in the Siberian Husky and through a sex-specific gene in Airedales. Different breeds, meanwhile, are more susceptible to different types of corneal dystrophy. Specifically:
Corneal dystrophy is found in Boston Terriers, Pembroke Welch Corgis, Shetland Sheepdogs and older Boxers (usually 7 years of age or older).
Epithelial/Stromal dystrophy occurs in Airedales, Afghan Hounds, American Cocker Spaniels, Basenjis, Beagles, Bearded Collie, Bichon Frise, Briards, Cavalier King Charles Spaniels, Dachshunds, English Springer Spaniels, German Shepherds, Golden Retrievers, Irish Wolfhounds, Labrador Retrievers, Miniature Pinschers, Nova Scotia Duck Tolling Retrievers, Rough Collies, Samoyeds, Siberian Huskies, Vizslas.
Endothelial dystrophy is found in Basenjis, Boston Terriers, Chihuahuas, Chow Chows and Dachshunds.
Many corneal dystrophies do not affect the animal's vision and therefore require no treatment. If there are erosions or ulcers on the cornea, however, the dog may squint, produce excessive tears and/or paw at the affected eye. Boxers and Shetland Sheepdogs are more prone to developing these erosions. Treatment in these cases is designed to cure the lesions through topical medications applied directly to the eye. For endothelial dystrophy, treatment is needed if the dog develops a complication known as "water blisters," which are painful buildups of fluid in the eye. These can rupture and cause wounds on the surface of the cornea. If topical medications do not control the problem, then surgery may have to be performed.