Why Do Kittens' Eyes Change Color? The Science Behind the Feline Eye Transformation

Kittens are known for their striking blue eyes, which eventually change to other beautiful colors - but when exactly does this happen and what determines an individual kitten's adult eye color? Most kittens' eyes start changing color around 6-7 weeks old. By 7-12 weeks, the permanent eye color is set based on pigment levels. All kittens are born with blue eyes because they haven't developed the pigment to determine their final eye color, but the more pigment a kitten has, the more likely their eyes will be green, yellow, orange or brown.

While the timing and outcome of this transformation is primarily determined by genetics, there are several studies that shed light on the specifics of this fascinating process. We'll explore the scientific literature in genetics, veterinary medicine and developmental biology to get a comprehensive understanding of feline eye color changes. This includes a deep dive into coat patterns, breed dispositions, and the biological reasons why a kitten's initial blue eyes will eventually turn into green or amber eyes. This exploration of the science behind the feline eye color transformation will provide a better understanding of melanin production, pigmentation and the other factors that determine our pets' eye colors.

Genetics of Kitten Eye Color

The genetics of a kitten's eye color are a complex mix of pigments, mutations, and evolutionary history. A kitten's adult eye color is largely determined by genetics and the presence of melanin pigment in the iris, per a study cited by Catster. Genes control the type and number of pigment cells (melanocytes) in the iris, which in turn determines how light or dark the color will be.

Genetic mutations that reduce melanin production are responsible for the blue eyes of certain cat breeds like the Siamese, as explained by PetMD. Meanwhile, the genetic condition heterochromia, which causes a cat to have two different colored eyes, can be due to genetics that affect the distribution of pigment in the iris, per The Tiniest Tiger.

Incredibly, a recent study published in Science has shown that the wide range of eye colors in cats today may have originated with a distant ancestor that had an unusually wide range of eye colors. A study using iNaturalist data determined that the ancestral cats had brown and gray eyes, with more vibrant colors like green and yellow evolving independently at least 16 times in different lineages. This genetic ability to create such a wide range of colors may be why we find cats' eyes so mesmerizing.

When to Monitor the Kitten Eye Color Change

Since kittens' eyes open between 7-10 days after birth, you can start monitoring eye color early on, says Fetch Pet. Between 4-8 weeks, you'll see some color as melanin is deposited, notes Noots Pets.

While most kittens will have their permanent eye color by 3-6 months, it can take up to a year for a kitten's eye color to fully settle into its final shade and depth, according to Daily Paws. This means that monitoring the color change can help catch any vision problems early.

Abnormal Eye Color Changes and Health Issues

If a kitten's eye color changes drastically after 3-4 months, it may be a sign of an underlying health issue, says VetInfo. Eye infections such as uveitis can cause redness, cloudiness, and discoloration, according to PetMD. Glaucoma, which is an increase in the eye's internal pressure, can cause the eye to look cloudy and white, according to the ASPCA.

Eyes that appear copper or yellow in color may indicate liver disease or metabolic issues, says the Trumann Animal Clinic. If a cat's eye color changes suddenly and without explanation, it's important to take them to the vet, as this could be a sign of a more serious health issue. Make sure to keep a close eye on a kitten's eye color as it changes so that you can catch any potential problems early.

How to Care for Kitten Eyes During the Color Change

While the color change is happening, it's important to make sure that your kitten's environment is clean and safe. The Brookhaven Animal Hospital recommends keeping newborn kittens away from bright lights that could potentially hurt or damage their eyes while they're still developing. Regular cleaning with a warm, damp cloth can also help ensure that any potential eye infections don't cause the eyes to become crusted shut, according to the McAllen Kitten Veterinary Care clinic.

The Cornell Feline Health Center notes that cats' eyes are especially sensitive to injury and disease, so make sure to keep an eye out for signs of vision problems, including excessive squinting, tearing, or pawing at the eyes. Regular vet visits will also help you keep an eye on your kitten's eye health and development during this time.

With a clean, safe environment and a watchful eye for any potential vision problems, kitten owners can make sure that their pet's eyes stay healthy as they change from their initial color to the beautiful shade they'll have for the rest of their life.

Conclusion: Enjoying the Feline Eye Kaleidoscope

Kittens' eyes open between 7-10 days after birth, which means that you can start checking out their eye color pretty early on. Between 4-8 weeks, you'll see the first signs of color as melanin starts to be deposited. While most kittens' eyes have settled on their permanent color by 3-6 months, it can take up to a year for the color of a kitten's eyes to fully mature and stabilize. Daily Paws notes that keeping an eye on the color change can help you catch vision problems early.

The vast majority of kittens are born with blue eyes due to a lack of pigment. As Daily Paws points out, this is because pigment doesn't start to be deposited in the iris until a few weeks after birth. Some cats will keep their blue eyes into adulthood, depending on their breed. Basepaws explains that breeds like the Balinese, Birman, and Siamese have fewer melanocytes, which allows them to keep their beautiful blue eyes.

A cat's eye color is determined by a combination of genetics and the production of pigments like melanin. Basepaws notes that the genes that control pigment cells can create a wide range of colors, from green and amber to the rare condition of heterochromia, where a cat has two different colored eyes. This genetic variation that allows for such a wide range of colors may be the secret to the mystery of the cat's mesmerizing gaze.

According to the Cornell Feline Health Center, cats' eyes are susceptible to a number of injuries and diseases that can affect their vision. If a cat's eye color changes dramatically after 3-4 months, it could be a sign of an issue like uveitis or glaucoma. It's important to keep a close eye on a kitten's eye color as it changes to make sure that any potential issues are caught early.

While the color of a cat's eyes is just one small part of what makes them unique, it's a great example of the diversity of the feline species. Watching a kitten's eyes change color is one of the many joys of cat ownership and cat friendship.