White Cats and Deafness
There is an established link between the white coat color, blue eyes and deafness. The deafness is linked to the gene for blue-eye(s) and not to odd-eyed cats. Not all blue-eyed whites will be deaf since there are several different genes causing the same physical attributes (whiteness, blue-eyedness) so it all depends on the cat's genotype (its genetic make-up) not its phenotype (its physical appearance).
Some people claim that 99% of blue-eyed white cats are deaf. This is inaccurate because blue-eyedness and whiteness can both be caused by different genes. It all depends on what genes the cat has inherited. These are the actual figures from scientific studies around the world. The percentages are given in ranges because results are different in different areas, partly because of the different genes found in the cat population. Where a cat is classed as deaf, the deafness may affect one or both ears.
- 95% of the general cat population is non-white cats (i.e. not pure white) and congenital deafness is extremely rare in non-white cats.
- 5% of the general cat population is white cats (i.e. pure white). 15-40% of these pure white cats have one or two blue-eyes.
- Of those white cats with one or two blue eyes, 60-80% are deaf; 20-40% have normal hearing; 30-40% had one blue eye and were deaf while 60-70% had one blue eye and normal hearing.
- Of the 5% of white cats in the overall population, 60-80% had eyes of other colors (e.g. orange, green). Of those 10- 20% were deaf and 80-90% had normal hearing.
- Deaf white cats with one or two blue eyes account for 0.25 - 1.5 of total cat population
- Total number of cats with white coat and blue eyes account for 0.75 - 2.0% of total cat population
It is evident from those studies that blue eyed whites exhibit a higher incidence of deafness than do orange/green eyed whites or non-white cats! But not all blue eyed whites are deaf and here's why:-
There is a known link between white coat color, blue eyes and deafness - but since the coat and eye color can be caused by different genes it means that only some blue eyed whites are deaf. There is a gene/gene complex which causes white coat and blue eyes; it is linked to deafness, but not all cats get white coat and blue eyes from this particular gene. These cats have a reflective layer called the tapetum in the eye (green eye with flash photography), differentiating them from the Siamese blue eye.
If the cat is a Foreign/Oriental White, it carries the gene for 'Siamese Blue Eyes' which is not linked to deafness (the gene for Siamese Blue Eyes is linked to cross-eyes instead). Siamese blue eyes lack a reflective tapetum and give red-eye with flash cameras. Random matings can mean that this gene sometimes appears in non Oriental-looking cats which have Colorpoint cats in their ancestry.
Albino cats are also white. True albinism causes pinkish eyes, but some albinos or partial albinos have pale blue eyes. There are too few albino cats studied to draw firm conclusions, but this mutation is not necessarily linked with deafness. It is also hard for a cat owner to determine whether their cat is a blue-eyed albino cat rather than an ordinary blue-eyed white.
(Continued on next page)