Cat eye color is important to breeders of purebred cats. The colour is referred to in the breed standards4 and is sometimes linked to coat colour. An example of linkage might be silver tabby cats that are often required to have green eyes3. For instance, the breed standard for the Russian Blue is described as:
“Vivid green. Set rather wide apart, almond in shape, not small and deep set”…1
|Russian Blue Cat|
“EARS: strikingly large, pointed, wide at base; continuing the lines of the wedge….Eye color: deep vivid blue”
The above applies to the Modern Siamese cat. We know that Siamese cats have blue eyes.
Left: This is not a Modern Siamese but a Traditional Siamese.The eye color is a deep vivid blue in line with the CFA eye color standard for the Modern Siamese cat.
Although, I suspect that the color balance of this photo favours blue! Photo: Juergen Kurlvink
In fact the only eye colour that is naturally linked to coat colour is blue. Blue eyes are caused by “forms of albinism” 3 that results in lack of pigmentation in the iris of the eye and coat. The iris is the part of the eye that we see that produces the colour of the eye. It controls the amount of light that the eye lets in.
Eye colour in cats in more apparent than it is for humans because their eyes are larger in relation to their heads. A cat’s eyes are unusually large. If human eyes were of comparable size in relation to the head, they’d be several inches in diameter, it is said. The cat’s large eyes give them a baby-like appearance.
Apparently green eyes or eyes with shades of green have become common in random bred cats (moggies).
Kittens are often born with blue eyes which change colour when they become adults. This is because eyes without pigment in the iris look blue due to scattered light. When pigmentation develops the eye takes on a color.
There is a wide range of eye colours from copper at one end of the spectrum to blue at the other. There are also odd eyed cats. This condition is caused by the gene that produces coats that are either totally white (dominant white gene) or spotted white (white spotting gene or piebald gene).
Here is a range of cat eye color:
|Odd-eyed Cat Photo: by sly06 (Flickr)|
As mentioned, cat eye color is formed in the smooth muscle cells of the iris. The iris creates the pupil, the aperture in the center of the eye that lets the light in to the retina in a controlled manner.It is the amount and intensity of pigmentation that is in the front and rear of the iris that determines cat eye color.
Odd-eye color is called complete heterochromia. It is caused by the dominant white gene. A rarer form is sectoral heterochromia when each eye has two colors: blue (or no color) and orange or yellow. Blue is caused by light refraction not pigmentation.
Some other instances where eye color is specified by the breed standard would be:
Nebelung: Color: Green with yellow/green mixture allowed. In kittens, changing from yellow to green. Should show green halo around pupil by 8 months. As vividly green as possible at maturity, which could be at 2 years or more. The more richness and depth of color, the better (TICA breed standard verbatim).
Turkish Van: Color is amber, blue or odd eyed.…Allow for faded eye color and greenish cast to amber eyes in cats over 18 months of age (TICA breed standard verbatim extracts).
There are many more. Start here for articles on all the cat breeds.
There is one last point to make. The true albino cat as opposed to the all-white cat (carrying the dominant white gene) has no pigment in the eye and therefore it looks pink:
Cat eye color – Associated pages:
Cat eye color – Notes:
1. russianblue.org.uk – Russian Blue Breeders Association
3. The Encyclopedia Of The Cat by Dr Bruce Fogle
4. Breed standards are the guidelines issued by each cat association as to the requirements regarding the appearance of individual registered breeds.