Deaf white cats are domestic cats with a pure white coat. Some all-white cats suffer from congenital deafness caused by a degeneration of the inner ear. This condition can occur in cats with yellow, green and blue irises, although the chances of deafness are dramatically increased with blue irises. In white cats with mixed-coloured eyes (odd-eyed cats), it has been found that deafness is more likely to affect the ear on the blue-eyed side. White cats can have blue, gold, green, or copper coloured odd eyes.
In one 1997 study of white cats with varying degrees of hearing deficiency, 72% of the animals[clarification needed] were found to be totally deaf. The entire organ of Corti was found to have degenerated within the first few weeks after birth; however, even during these weeks no brain stem responses could be evoked by auditory stimuli, suggesting that these animals had never experienced any auditory sensations. It was found that some months after the organ of Corti had degenerated, the spiral ganglion also began to degenerate.