LATE EYE COLOUR CHANGE TO BLUE
Kittensí eyes naturally change from infant blue eyes to the adult colour around 6-8 weeks old, often not reaching their final adult hue for many months. More rarely an adult catís eyes change back to blue. In the case of white or white-marked cats, one eye may remain blue Ė this is congenital heterochromia and is related to the genes that produce white fur.
I canít find any information on both eyes changing colour at the same time, but there is a similar condition in humans called acquired heterochromia iridis where one eye (rarely both) changes colour later in life. In humans, loss of eye pigment is often associated with illness or trauma. Because the cat mentioned here has been examined and is healthy, it is more likely that there is a random mutation and the iris has simply stopped producing pigment.
Batu is a tawny spotted castrated male Ocicat, born in June 2014. His breeder, Ulla Haapanen, received photos of Batu from his owners, showing that his eye colour has slowly changed within the last year from yellow-green to blue. The gradual change began at the age of 2 years and progressed within a year. By March 2017 he had vivid blue eyes. All five of Batuís full siblings have normal yellow or green eye colour, as do his parents.
Neither of the cat's parents carry a colourpoint gene and there is no white spotting. Vitiligo (depigmented patches) most usually shows as random white patches on the coat and is not usually symmetrical.
According to the vet, thereís nothing wrong with Batu. He went to see a vet who specialised in eye diseases. Batuís intra-ocular pressures were normal (this is not glaucoma), his eyesight is normal, his eyes are completely fine Ė they are just clear blue instead of yellow-green. Because he is a neuter, it isnít possible to see if the condition can be passed on genetically.
Unless any reader knows differently, Batu is a one-off. His eyes changed from baby-blue to yellow-green in the normal way, but later changed to vivid blue.