deafness

A cat' s ears may be afflicted by hardening of the duct, accumulation of wax, perforation of the eardrum, catarrh - all disturbances which can lead to deafness.

SOURCE: cats.consultinghealth.com

Although deafness is relatively rare in cats in general, white cats can frequently be deaf, especially blue-eyed white cats. As they won't be able to hear vocal signs from you, you may need to use more visual signs when communicating with them. Cats with diseases in their ears, such as polyps, may have reduced ability to hear.

SOURCE: cats.org.uk