In 1868, Charles Darwin wrote in his book (The variation of domesticated animals and plants): "If white cats have blue eyes, they are almost always deaf."
Charles Darwin was right, since between 56% and 90% of white cats with blue eyes are deaf in one or both ears.
Deafness is caused by the absence of a layer of cells in the inner ear, and these ear cells are formed from the same stem cells that make up the Tapetum and the melanocytes that color the fur
If these cells do not form, the melanoblasts do not reach the ear, the eye, or the skin, or they will arrive in insufficient quantities, so the hair cells will not develop as they should and the animal will be deaf. In addition, as melanocytes will not develop, the animal will be white and will have a clearer pigmentation for the eyes.