Cats have some of the most fascinating eyes in the animal kingdom. Their vertical pupils, sharp feline shape and range of beautiful cat eye colours are truly mesmerising. Moreover, cats communicate with their eyes, making them a true window into the soul. Most kittens are born with beautiful baby blue eyes, but while some breeds, like the Siamese, keep the blue hue, most cats' eye colours will change. But when and why does this happen?
Why do kittens have blue eyes?
While a kitten's blue eyes may add to their cuteness, the colouration is actually due to a lack of melanin, which is the pigment responsible for determining eye colour. In newborn kittens, the melanin-producing cells in the iris, the coloured part of the eye, are underdeveloped, giving the characteristic blue hue. Gradually, as the kitten grows and these cells mature, they begin producing melanin, causing the kitten's eye colour to change. If the melanin production increases, the eye colour will be darker. However, melanin levels can also be influenced by genetic factors or environmental influences, causing slight changes from blue to yellow, green or amber eyes.
Do kittens' eyes change as they grow?
Like a lot of mammals, kittens are born with their eyes closed. When they eventually open their eyes, which is usually around seven to 10 days old (but also known to happen around 16 days old), they are usually a stunning blue colour. However, their eyes may not be blue for long. As kittens grow, their eye colour can transform, and the blue fades to give way to their permanent eye colour, which could be anything from green to gold. This usually happens from around four to eight weeks old.
When do kittens' eyes change colour?
While the exact timing will vary, a kitten's eye colour will typically start changing between six and eight weeks of age. But for some felines, it could start earlier; for others, it may take a bit longer. The transformation from blue to its eventual hue involves the development of cells in the iris called melanocytes, which produce melanin.
How to predict a kitten's eye colour
Predicting your kitten's eye colour is not an exact science and you'll need to know the kitten's parents and the colour of their eyes. While most kittens are born with blue eyes, genetics play a key role in eye colour in cats, with certain genes influencing whether a kitten will eventually have blue, yellow, green eyes or another colour. For some breeds, it's easier to tell what a kitten's permanent eye colour will be. For example, some cats, such as the Siamese, Ragdoll and Tonkinese, continue to have low levels of melanocytes as adult cats and will, therefore, keep their blue eyes. When your kitten is three months old, they will have their permanent eye colour.
How to tell a kitten's age based on their eyes
A vet doesn't typically use a kitten's eyes to tell their age, as it's not always an accurate indicator. They usually look at the feline's teeth to approximate their age. However, you can use their eyes to guide how old a kitten will likely be. For instance, newborn kittens typically have closed eyes. They only start to open their eyes at around one to two weeks old. Their eyes will likely be blue at this stage. By the age of around three weeks, a kitten's eyes are fully open. As the kitten continues to grow, their eye colour will start to change. By around the age of eight weeks, most kittens will have developed their permanent eye colour. However, this transition can vary from one kitten to the next.
Once these cells become fully functional, they develop your cat's permanent eye colour. Factors such as the environment, genetics and your kitten's overall health can affect the speed at which their eyes change colour. Furthermore, some cat breeds will retain their blue eye colour as adult cats, so they won't go through this change.
