White cats with blue eyes are beautiful animals, but they can suffer from a genetic defect that causes them to spend their lives in silence.

Most blue-eyed white cats are born deaf. This does not mean that all white cats with blue eyes suffer from the condition, and it does not affect Burmese and Siamese breeds that are very light colored with blue eyes. Many cats with one blue eye and one yellow eye also are prone to deafness.

The cause of the deafness is a dominant genetic defect. Every animal has two genes for each trait, one from their mother and one from their father. In this specific deafness, if the mother passes on a gene for deafness and the father passes on a gene for hearing, the deafness gene is dominant and the kitten will not be able to hear.

Inside a cat's ear, there is an organ that converts sound waves into electrical impulses that travel to the brain and are processed as sound. In this type of genetic defect, the organ responsible for the conversion starts to degenerate at about 5 days of age. Since a normal kitten's ear canal does not open until they are 6 to 14 days of age, the kitten affected with this gene never hears.

The same gene also affects the cat's eyes by preventing the normal formation of the retina. This means that these cats have reduced ability to see at night and their hunting abilities are greatly hindered.

As with other deaf animals, deaf cats tend to be very alert and may be more aggressive and more vocal than other littermates. Special care should be taken with deaf cats. They should remain indoors and not be allowed to roam. Also, in order to prevent passing this gene to future generations, it is strongly recommended that affected cats should not be bred.