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).
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.