A cataract is any opacity in the lens of the eye. The dog’s normal lens is translucent (clear), and it transmits and focuses light onto the retina in the back of the eye. A cataract within the lens may block the transmission of light to the retina.
There are many causes of cataracts. The most common form of cataracts in the dog are genetic, inherited types. For genetic cataracts, the age of onset and severity varies among the various breeds of dogs.
Cataracts may also develop following trauma to the eye, in association with metabolic diseases such as diabetes, from nutritional disorders during puppy hood, or secondary to other eye diseases. Cataracts may develop spontaneously in old age, but should not be confused with nuclear or lenticular sclerosis, an aging change that often occurs in the canine lens and does not cause blindness. Rarely cataracts may develop following exposure to certain drugs, toxins, concentrated microwaves, radiation, or following electrocution.
Cataracts cause varying levels of vision impairment and may lead to blindness.
What to Watch For
Bluish, gray or white color change inside of the eye
Tendency to bump into things
Reluctance to use stairs or jump up onto objects
Hesitancy in unfamiliar environments
Other signs of blindness
Inflammation or redness
Pain and squinting due to the underlying cause
Diagnosis of Cataracts in Dogs
Diagnostic tests are necessary to recognize cataracts and exclude other diseases. Tests may include:
A complete medical history and physical examination.
A complete eye examination. Most veterinarians have the tools with which to confirm the presence of a cataract in the lens, but it is often necessary to visit a veterinary ophthalmologist to have a more thorough examination performed using an indirect ophthalmoscope and a slit lamp biomicroscope.
Blood tests to determine any underlying causes
An ultrasound examination of the eye if the cataract is too opaque to allow examination of the retina.
Possibly an electroretinogram to evaluate the function of the retina, especially if the cataract blocks visualization of the retina.
Treatment of Cataracts in Dogs
There is no medical treatment available to reverse cataracts, to prevent cataracts or to shrink cataracts.
Cataracts that are inherited or are not complicated by other eye diseases may be surgically removed. Cataracts associated with other eye diseases, such as inflammation (uveitis) cannot be removed surgically until the inflammation is brought under control.
Whether a dog is a candidate for cataract surgery can be determined by a veterinary ophthalmologist.
Treatment must also be instituted for any underlying causes, such as diabetes, etc.
Home Care and Prevention for Dogs with Cataracts
It is important to have all dogs with cataracts examined early in the course of their disease to determine whether the cataract is inherited or is secondary to other conditions. It is also important to determine whether the cataract itself is affecting the eye, such as causing inflammation or glaucoma. Early evaluation by a veterinary ophthalmologist allows appropriate therapy to be instituted for ancillary problems and allows a determination to be made as to whether the dog is a candidate for cataract surgery.
If your dog has inoperable cataracts, he may require help in adjusting to his blindness. Be sure to keep objects around the house in a consistent place. Confine the dog to a fenced yard or leash walking. Most blind pets function extremely well in familiar environments.
There is little you can do to prevent cataracts. If your pet is diagnosed with inherited cataracts, notify the breeder so that no other litters are produced from the same sire and dam.
If your dog is diagnosed with diabetes, then monitor blood and urine sugar as recommended by your veterinarian. Maintain good control of the diabetes.
Information In-depth for Dogs with Cataracts
Various eye diseases can cause a cloudy white appearance similar to that observed with cataracts. Many such diseases result in poor vision or blindness. Your veterinarian or veterinary ophthalmologist will be able to tell you if the white appearance and vision loss is caused by cataracts, by disease of the cornea (the clear outer covering of the eye), or the retina ( the specialized light receptor layer in the back of the eye).
Causes of Cataracts in Dogs
There are several causes of cataracts including:
Genetic. Cataracts in dogs are frequently inherited. Over 40 breeds of dogs are known to be predisposed to cataracts, including retrievers, spaniels, poodles, schnauzers, terriers, bichon frises, Siberian huskies and Old English sheepdogs. The Canine Eye Registration Foundation (CERF) maintains statistics on breeds of dogs and their reported eye diseases in order to make breeding recommendations (www.vmdb.org….click on CERF). In general, if a dog has cataracts and no other plausible cause can be determined, the cataracts are thought to be inherited.
For some breeds, there is a considerable experience regarding the natural history (progression) of disease. For example, in the golden retriever, cataracts are frequently centered in the back of the lens and tend not to progress. In the Boston terrier, cataracts may first be noted by 6 months of age and can rapidly progress causing blindness by age 2. In the bichon frise, cataracts may not be evident until the dog is 4 years old, and then the rate of progression is variable.
Trauma. If the lens is punctured or damaged from something like a cat scratch or a stick penetrating the eye, a cataract usually forms. Some of these form only at the site of injury, but others progress to involve the entire lens.
Diabetes. Diabetes mellitus (sugar diabetes) is a systemic disease in which regulation of blood sugar (glucose) is not controlled. The lens requires some glucose, but when the levels are too high, cataracts can form rapidly. Diabetic cataracts can develop even when an animal is receiving insulin.
Congenital, developmental cataract. Animals can be born with cataracts, but they are not necessarily inherited (genetic) cataracts. There may have been a problem in the development of the lens or of the blood vessel that surrounds the lens as it develops during the pregnancy.
Old Age. Age related cataracts are usually very small and tend to progress very slowly. A true senile cataract is not the same as the natural aging of the lens that gives it a bluish-white hue known as nuclear or lenticular sclerosis.
Secondary to other diseases. Retinal diseases such as progressive retinal atrophy and inflammatory eye diseases, such as anterior uveitis can cause cataracts. The underlying eye disease alters the nutrition of the lens, and a cataract forms. Nutritional deficiencies early in life, changes in blood calcium, exposure to certain drugs and toxins, exposure to concentrated microwaves, radiation therapy and electrocution may also alter both the nutrition and the structure of the lens, resulting in cataracts.