Congenital sensorineural deafness is a degeneration of the inner ear that causes deafness. A 1997 study examined many white cats and found that 72% of the animals were completely deaf. The scientists found that most of these animals where deaf at birth; their ears never had the ability to process any auditory signals. While this syndrome CAN occur in white cats with green eyes, it is was actually determined that the ear is more likely to be non-functional whenever it is next to a blue iris. -> Visit this link for further reading.