Corneal Dystrophy

Corneal dystrophy is an opacity in the cornea (clear covering of the eye). In Samoyeds it is typically in both eyes with lipid deposits in the “stromal” layer of the cornea. It is suspected to be an inherited disorder. Corneal dystrophies may also occur in the epithelial or endothelial layers of the cornea.

The term corneal dystrophy is sometimes used to describe a similar disorder, corneal degeneration. This also is an opacity in the cornea, but is not inherited, may only be in one eye, and may be accompanied by inflammation. The opacity is caused by deposits of lipid, cholesterol or calcium.

Signs and Symptoms

Corneal dystrophy and degeneration are seen as opaque areas in the normally clear cornea. The age of onset of corneal dystrophy in Samoyeds is typically between 6 months and 2 years.

Causes

Corneal dystrophies are suspected to be inherited in Samoyeds and some other breeds. Corneal degeneration is secondary to injury or other eye disorders, or to systemic disorders such as high cholesterol or calcium levels. These can cause deposits of lipid or calcium in the cornea.

Risk Factors

Corneal dystrophies: Related dogs with the disorder.

Diagnostic Tests

Corneal dystrophy and degeneration are evaluated by visual observation of the surface of the eye with a bright light. If an associated corneal ulcer is suspected, a fluorescein dye test may be performed. The yellow-green dye is applied to the eye; ulcerated regions retain the dye and look bright green.

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

Most stromal dystrophies, the type typically seen in Samoyeds, do not cause discomfort or interfere with vision; treatment is usually not required. If complications such as erosions/ulcers develop, a veterinarian can prescribe antibiotic drops/ointment. Endothelial dystrophies often lead to fluid buildup (edema) in the cornea with inflammation, reduced vision and corneal ulcers. Treatment is symptomatic. Edema can be treated with a high-salt ointment (hyperosmotic); ulcers can be treated with antibiotic drops/ointment. Treatment of corneal degeneration depends on the cause, if determined, and the specific symptoms. Various types of eye drops or ointments may be used to reduce inflammation, lessen calcium deposits or treat associated ulcers. Rarely, surgery is recommended to replace part of the cornea (graft), but this procedure does not work as well in dogs as in humans.

Management

Keep a lookout for discomfort or any excessive discharge from the eyes, and see your veterinarian or a veterinary ophthalmologist. Because corneal dystrophy is suspected to be an inherited disorder, affected dogs should not be bred; their close relatives should probably not be bred either. Samoyeds used for breeding should be examined each year by a board certified Veterinary ophthalmologist. If free from heritable eye disease they may be certified by the OFA Eye Certification Registry. The certification is only valid for 12 months, then the dog must be reexamined to be recertified.