Endothelial Degeneration With Corneal Edema in Dogs
Also called corneal dystrophy, endothelial degeneration is an inherited optic disorder in dogs that can present as a cloudy, swollen cornea. Not usually painful to the dog, this is a relatively rare disease that can often be traced to systemic conditions such as hypothyroidism, Cushing's disease or disorders involving the metabolism of cholesterol.
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Causes
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Corneal dystrophy in dogs involves a malfunction of the endothelium (the inner layer) of the cornea when cholesterol lesions become deposited between it and the framework of the eye. Cholesterol deposits can cause a hardening, or dystrophy, of the cornea, much as they do in coronary arteries. The pumping mechanism that moves the serous fluid around the eye prematurely degenerates and the cornea becomes cloudy with a "ground glass" appearance.
Disease Symptoms
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Endothelial degeneration results in accumulation of fluid (edema) in the cornea. This causes a change in color from clear to a milky, opaque color usually starting in one corner and eventually spreading over the entire eye. As the cornea swells, it becomes more prone to ulceration, inflammation and injury. If the cornea becomes inflamed, the dog may begin squinting and tearing as the eye becomes painful.
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Diagnostic Tests
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A complete veterinary eye examination is usually recommended to rule out all other causes of corneal edema. Because a diagnosis of endothelial dystrophy is relatively rare, other diseases such as glaucoma, uveitis, and trauma must be ruled out as causative factors. Once other diseases have been eliminated, the breed and age of the dog are used to typify the disease.
Treatment
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This canine disease is progressive and irreversible. There is no effective way to return the eye back to normal; treatment is usually administered to slow progression of the degeneration and to treat symptoms. Veterinarians may recommend a hypertonic (very concentrated) sodium chloride ointment or solution to prevent edema in the cornea and keep the surface layer of the eye healthy. This medication is commonly given for life. Antibiotics may be indicated if ulcers or inflammation develop.
Considerations
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Endothelial degeneration is an inherited, bilateral (both sides) disease in dogs. Although it is found in all dog breeds, it is most commonly observed in Chihuahuas, Boston terriers and dachshunds and is usually diagnosed in younger dogs between the ages of three and six years.
Warning
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While this particular optic disease is not usually painful, resulting conditions such as corneal ulcers and abrasions can be, and need to be considered veterinary emergencies if they occur. Endothelial degeneration rarely results in total blindness, but some dogs may develop a small blind spot around the cholesterol lesions.
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