Cats can experience a natural color change in their eyes as they grow from kittens into adults. While some cats maintain blue eyes throughout adulthood, many cats that are born with blue eyes will develop green, yellow, or amber eyes as they mature. The specific timing and nature of these eye color changes depends on the cat’s genetic makeup. With a bit of knowledge about feline eye anatomy and development, cat owners can better understand why their cat’s eye color may shift from blue to another hue.
Kitten Eye Color
Kittens are often born with blue eyes. The blue eye color is caused by a lack of pigment in the iris, revealing the blue color produced by light reflecting off the back of the eye. Since kittens’ eyes are still developing at birth, they may not yet have enough pigment to produce their permanent eye color.
As the kitten matures, cells called melanocytes begin to produce melanin, which is the pigment responsible for eye color. The melanin gradually fills in the iris, changing the eye from blue to the adult color. This process is typically complete by the time a kitten is around 6-8 weeks old, but full pigmentation may take up to 16 weeks in some cats.
Final Eye Color
A cat’s final, adult eye color depends on genetics. The main gene involved is the Color gene, which has several variants affecting eye color:
- The B variant produces amber, green, or hazel eyes.
- The b variant produces blue eyes.
- The C variant allows full expression of color which can produce brilliant copper or gold eyes.
Kittens inheriting two b variants will likely retain blue eyes in adulthood. Kittens with one or two B variants will develop golden, green, or amber eyes as pigment fills in. The specific resulting eye shade depends on whether other genetic factors dilute the color. Silver tabby cats, for example, often retain a brilliant gold or copper eye color due to the presence of both B and C variants.
Changes from Blue to Green or Yellow
Since the majority of kittens are born with blue eyes, the most common eye color change is from blue to green, yellow, gold, or amber. This occurs because most cats have at least one copy of the B variant. Here is an overview of typical eye color transitions:
- Blue to green – Kittens with a primary eye color of green will initially have blue eyes that transition to green as melanin develops in the first few months of life.
- Blue to yellow/gold – Kittens with a primary eye color of golden or yellow will have blue eyes at first that change to gold or yellow as pigment fills in.
- Blue to amber – Kittens with a final eye color of amber will be born with blue eyes that turn amber or orange starting around 6-8 weeks of age as melanin increases.
The timing varies based on the cat’s genetics, but most kittens complete the transition from blue to their permanent, adult eye color between 6-16 weeks of age. Some cats may retain a small amount of blue in their eyes throughout adulthood.
Changes from Green to Gold/Yellow
While less common than blue to gold/yellow transitions, some cats will exhibit an eye color change from green to gold or yellow. This often occurs in breeds with green eyes, like the Russian Blue. A kitten may be born with grey-blue or greenish eyes that transition to more brilliant, vivid yellow-green eyes by adulthood.
Reasons for Gradual Color Change
Cat eye color changes gradually rather than instantly. Here are some key reasons why it takes time for kittens’ eyes to transform from blue to their permanent, adult color:
- Melanocyte migration – The pigment-producing cells called melanocytes gradually migrate into the iris over weeks and months after birth.
- Melanin accumulation – Once melanocytes populate the iris, they must produce enough melanin pigment to effect a change in eye color. This pigment accumulation happens slowly.
- Eye development – Kittens’ eyes are still developing after birth, going through changes that support the maturation of various eye structures and functions.
While melanin increases significantly between birth and 4 months of age, research shows that kittens’ eyes continue to develop until around 6-8 months of age. This extended development supports the gradual nature of eye color transitions in kittens.
Factors Affecting Timing of Eye Color Change
While most kittens complete the transition from blue eyes to their permanent eye color between 6-16 weeks, some factors influence exact timing:
- Genetics – Kittens inheriting eye color genes for brilliant gold or copper will usually transition faster than those developing green or yellow eyes.
- Breed – Some breeds, like Siamese, tend to transition earlier while others, like Russian Blues, may transition slower.
- Birth eye color – Kittens with very dark blue eyes at birth tend to transition faster than those with light blue eyes.
- Coat color – Eye color change may happen earlier in cats with darker coat colors like black.
While genetics primarily determine the specific eye color outcome, other factors like nutrition and environment can also impact timing.
Do Cats’ Eyes Change Color After Kittenhood?
Once a kitten completes the change from blue eyes to their permanent adult eye color, additional changes are unlikely. However, there are a few exceptions:
- Dilution of color – Some cats experience a gradual dilution or fading of eye color later in life, usually due to the effects of aging or cataracts. This can cause green eyes to appear more yellow or amber eyes to lighten towards yellow.
- Eye injury – Trauma to the eyes can damage pigment-producing cells, reducing melanin levels and causing eye color to lighten.
- Diseases – Certain diseases impacting pigment production may result in color change in adult cats. One example is feline Chediak-Higashi syndrome, which causes a shift to blue eyes.
However, these scenarios do not represent a complete change to a new eye color outside the normal spectrum for the cat’s genetics. For example, an adult cat with green eyes is highly unlikely to develop brilliant copper-colored eyes later in life without an underlying condition or injury.
Why Does Eye Color Matter?
While eye color change does not directly impact vision or eye health, it can provide cat owners and veterinarians valuable information about a cat’s well-being and development. Understanding the typical timing and nature of eye color transitions allows for monitoring any potential issues. Reasons to note eye color changes include:
- New kitten care – Monitoring eye color gives clues about a kitten’s age and development.
- Breed standards – Some breeds, like Siamese, have expected eye colors as part of their breed standard.
- Medical conditions – Changes in adult cats may signify health issues like trauma, cataracts, or pigment disorders.
- Owner identification – Eye color helps owners identify their cat and may be useful for finding lost cats.
So while eye color itself does not directly impact feline health or vision, paying attention to a cat’s eye color and any changes can provide valuable insights for owners and veterinary care.
Conclusion
Kittens experience significant yet gradual eye color transitions as they mature from newborns into juveniles and adults. While many are born with blue eyes, most develop green, amber, yellow, or golden eyes over the first several months of life as pigment accumulates in the iris. Though adult cats’ eyes are unlikely to exhibit further color changes, exceptions can occur due to medical conditions. Understanding the normal developmental timelines of kitten eye color change allows owners to monitor their cat’s health and recognize any issues that may arise.
