Corneal Dystrophy in Dogs

There is sometimes confusion between corneal dystrophy and corneal degradation, which are similar in clinical symptoms, but corneal degradation is not thought to be genetic. Many breeds are affected by corneal dystrophy. Unfortunately, the condition appears to affect each breed differently. In all dogs, corneal dystrophy is caused by a genetic disturbance in how fat is metabolized. The result is a white or gray clouding of the eye. It generally starts in one eye but always affects both. In most breeds, it does not cause discomfort or blindness. In a smaller list of breeds the disorder is more progressive and can lead to more severe complications.

Corneal dystrophy refers to the clouding of the cornea from an inherited condition.

At the onset, corneal dystrophy usually appears as a white or grayish round “cloud” at the center of the eye. If ulcers are present the dog may give signs of irritated eyes, rubbing, and itching. The spots are usually round but sometimes donut shaped. Symptoms vary widely between breeds.  The affliction can seemingly appear at any age,in as little as four months in Airedale Terriers and as late as thirteen years in Chihuahuas. In some breeds, the trait is thought to be sex linked.

• White or grayish cloud in the center of the eye
• Irritated eyes

Types

There are many types of corneal disease and degradation. However, corneal dystrophy itself has not been further classified. Dogs affected with a slower, less severe version of corneal dystrophy are often:

• Siberian Husky
• Samoyed
• Cocker Spaniel
• Beagle
• German Shepherd
• Pointer
• Bichon Frise
• Poodle

Dogs who experience a more aggressive version of corneal dystrophy are often:

• Shetland Sheepdog
• Airedale Terrier
• Boston Terrier
• Dachshund
• Chihuahua

Corneal dystrophy is an inherited condition affecting the ability of the cells to process fat. It is an autosomal recessive trait, meaning both the dam and the sire must carry the gene in order for the puppy to be affected, at least in some breeds. In other breeds, the mode of inheritance appears to be sex-linked. In still other breeds, the mode of inheritance has not been identified.

Diagnosis is made from the observation of the lesion. This can be done by the use of a fluorescein dye which may clearly define the problem.  Further testing of the eye may include intraocular pressure and tear test. Blood work is often done to verify markers in the blood consistent with this condition, such as cholesterol. An eye specialist may be brought on board by your veterinarian to rule out other corneal diseases or degradation.

In most cases, treatment is not needed. If the condition does not progress rapidly, cause the dog discomfort, or affect vision, often the best course is to leave the eye alone. Your dog may notice the spot on his eye for a while but his brain will train him to see past it without annoyance much like your brain will do the same for you. 

Because the condition has to do with the process of fat, sometimes a low fat, high fiber diet is recommended. There is some disagreement among researchers as to whether or not a low-fat diet is effective. The general consensus is that the fat should be lower than 10% in dry matter (kibble) and adherence in all foods and treats is needed to see results. 

Sometimes in cases of corneal dystrophy a topical acid treatment (TCA) may be recommended. This treatment may be done once or more times to aid in comfort. It helps to dissolve the mineral deposits that leads to ulcers.

In severe cases of corneal dystrophy, surgery to remove the mineral deposits can be recommended. As with any surgery, complications can arise. At times, scar tissue remains where the mineral deposits were. Other more severe complications can lead to rupture of the eye or retinal detachment. Although complications are rare, some can lead to blindness. Because corneal dystrophy sometimes is associated with Cushing’s disease, testing for that should be done after diagnosis.

There is no real recovery from corneal dystrophy. Management, unfortunately, depends on the severity of the case. Most cases do not lead to severe discomfort for the dog and they can lead a normal life. There is currently no certification required of breeders to prove dogs in their breeding program do not possess the inherited gene. Unfortunately, because some dogs do not develop the affliction until later in life, it can be difficult to remove them from a breeding program before they have been bred many times, possibly affecting many dogs.