This is the loss of normal transparency of the eye's lens. The opacity is usually white but may also give bluish white cast to the lens behind the pupil. A cataract can be singular or multiple, of any size or shape and may affect the entire lens. The degree of vision impairment is determinded by the size and location of the cataract within the lens. While most cataracts are considered to be inherited, some may result from trauma to the eye or from metabolic disorders such as diabetes. Congenital (present at birth) cataracts may or may not be inherited and generally do not progress to blindness. Most hereditary forms of cataract occur in dogs under the age of 5 years. Senile cataracts in older dogs are quite common and are considered to be the result of the aging process. Like any other ocular abnormality, cataracts can be confirmed by an ophthalmological exam. In general, Swissy breeders will not breed a dog with cataracts unless trauma has been clearly established as the cause of the condition.