A cat’s eye color is determined mainly by genetics, with some breeds having distinctive and consistent eye colors. However, kittens are often born with blue eyes that can change color as they mature. Environmental factors and health conditions can also lead to shifts in eye color over a cat’s lifetime. While eye color is partly determined by genetics, it can be variable based on a cat’s age and health.
This article provides an overview of the various causes of cat eye color changes. We discuss normal kitten eye development, environmental impacts, diseases, breed tendencies, genetics, and common myths about feline eyes. Our goal is to comprehensively cover why cat eye colors can shift and change over time.
Causes of Eye Color Changes in Kittens
A kitten’s eye color begins changing around 4-8 weeks of age as melanocytes migrate to the iris and start producing pigment called melanin (1). This pigment causes the eye color to transform from blue to the adult color.
There are several factors that influence the final eye color of kittens:
- Genetics – Eye color is inherited from the parents, with some colors like green being more rare.
- Coat color – Kittens with white coats often retain blue eyes while those with orange coats usually develop green or hazel eyes.
- Environmental factors – Exposure to sunlight can cause melanin production and impact eye color.
- Diseases – Illnesses like glaucoma or corneal inflammation can cause structural changes that alter eye color.
Kittens with blue eyes at birth do not stay that way for long. As they mature, their eyes commonly change to green, yellow, orange or copper. In some cases, one eye may become a different color than the other (2). Monitoring eye color changes in kittens allows owners to catch any potential health issues early on.
(1) https://www.dailypaws.com/cats-kittens/health-care/kitten-care/when-do-kittens-eyes-change-color
(2) https://www.catster.com/guides/when-do-kittens-eyes-change-color/
Kitten Eye Development
Kittens are born with closed eyes. Their eyes typically open between 5 to 16 days old and are initially blue in color. According to the article When Do Kittens’ Eyes Change Color? from dailypaws.com, “The melanocytes that produce melanin—the pigment that gives eyes (and skin and fur) their color—migrate slowly across the iris until the kitten is around 4-8 weeks of age.”
During the first 2-3 weeks, kittens’ eyes are blue and may also appear crossed or misaligned as they learn to focus their vision properly. Around 3-5 weeks, as melanin production increases, their eyes will transition from blue to a green, hazel, gold or copper shade. By 6-8 weeks, the final adult eye color emerges. This is often yellow, green or orange for cats with orange/red coats. Cats with black fur typically develop vibrant yellow or gold eyes while cats with white coats often retain blue eyes.
While eye colors continue to gain intensity up to about 16 weeks, the final hue is established by around 2 months of age. Kittens’ eyes have usually completed the color change process by 12-16 weeks old.
Environmental Factors
A cat’s environment can influence subtle changes in eye color over time. One of the biggest environmental factors is light exposure. Kittens develop their mature eye colors as their irises are exposed to more light. Specific wavelengths of light can cause the production of different pigments. Exploring Feline Eye Colors: Genetics, Variations, and Care. More time spent outdoors in natural light versus indoors can deepen eye color.
The reflections and colors a cat sees in their environment may also slightly alter perceived eye shade. For example, a cat with hazel eyes spending time in a green forest may appear to have greener-tinged eyes than the same cat in a different setting. However, the eye color itself does not actually change.
While environmental factors can lead to subtle shifts in eye color, any drastic or sudden changes should be evaluated by a veterinarian. Rapid color changes or multicolored eyes could indicate inflammation, infection, trauma, or other health conditions affecting the eyes or vision. Monitoring eye color is important for assessing feline health and wellbeing.
Diseases Causing Color Change
Several feline eye diseases can cause a cat’s eye color to change or appear different. Two of the most common are cataracts and glaucoma.
Cataracts
Cataracts cause the lens of a cat’s eye to become cloudy, which blocks light from properly entering the eye. This results in blurred vision. As cataracts worsen, the eye’s appearance changes – the pupil, which is normally black, starts to look gray or blue as light is obstructed [1]. The eye overall develops a cloudy, bluish-gray tint.
Glaucoma
Glaucoma is a condition where pressure builds up inside the eye. This damages the optic nerve over time and can lead to blindness if left untreated. In addition to vision loss, glaucoma also affects eye color. Increased intraocular pressure causes the cornea to become edema, taking on a hazy, bluish-gray appearance [2]. The eye may also dilate fully with a fixed pupil.
Catching diseases like cataracts and glaucoma early maximizes the chances of preserving vision. So monitoring cats’ eyes for any color changes can alert owners to potential issues requiring veterinary assessment.
Breed Differences
There can be significant differences in eye color between cat breeds. Here are some of the most common eye colors seen in popular breeds:
Siamese: Known for their stunning blue eyes. The breed standard requires deep, vivid blue eyes.
Persian: Persians tend to have brilliant copper or green eyes, though other colors like blue are seen. Their round eyes are a defining feature.
Maine Coon: Eye colors include green, gold, copper, odd-eyed, and blue. Their eye colors are often bright and vibrant.
Ragdoll: Ragdolls typically have bright blue eyes, though some can be green, odd-eyed, or yellow. Blue eyes are part of the breed standard.
Scottish Fold: Scottish Folds can have almost any eye color, with gold and copper eyes being common. Their eyes are rounded and open.
Sphynx: Often yellow or green, though other colors are seen. Their eyes tend to be lemon-shaped and prominent.
Abyssinian: Usually have golden, green or hazel eyes. The almond-shaped eyes are a distinct feature.
Bengal: Eye colors include green, gold, hazel, and aquamarine. The exotic eye colors match their wild appearance.
Birman: Famous for their deep sapphire blue eyes, which is part of the breed standard.
Russian Blue: Their stunning green eyes are a breed hallmark. The vibrant green complements their silvery coat.
Eye Color Genetics
A cat’s eye color is primarily determined by two genes – the Orange gene and the Agouti gene. The Orange gene controls how much orange pigment is produced, while the Agouti gene controls whether black pigment is produced. There are different variants of these genes that lead to different eye colors.
The main variants of the Orange gene are:
- OO or O – Produces maximum orange pigment, leading to orange or copper colored eyes
- oo – No ability to produce orange pigment, restricting eye colors to shades of green, blue, or gold
The main variants of the Agouti gene are:
- AA or A – Allows for production of black pigment
- aa – Restricts eye color to shades of orange, yellow, or green by inhibiting black pigment
By inheriting different combinations of these gene variants from their parents, cats can have a wide range of possible eye colors. For example, a cat that inherits OO and AA can have brilliant orange eyes, while one that inherits oo and aa will have green eyes without any orange.
[Bepaws.com Eye Color Article]
Owner Perception
Many cat owners report perceiving changes in their cat’s eye color over time. However, research shows cat eye colors are generally stable, outside of gradual lightening with age. Why do some owners vividly recall their cat’s eyes transforming from one color to another?
According to a Quora discussion, the tapetum lucidum, a reflective layer in a cat’s eye, can cause the eyes to appear different colors depending on the lighting and angle. This optical illusion likely explains many cases of perceived eye color changes.
Additionally, human memory is malleable and imperfect. Owners may vividly remember their cat’s eyes as one color, then convince themselves the eyes changed color, when in fact they were mistaken about the original eye color. Memory biases and the passage of time can alter recollections.
While cats’ moods and emotions do subtly alter their eye appearance, true color changes are rare. Gradual lightening of eye color from kitten to adult is normal. But cat owners should not expect dramatic eye color shifts over time. What seems like a change is likely an illusion or false memory.
Myths
There are some common myths and misconceptions surrounding cat eye colors that persist today:
One myth is that a kitten’s eye color will stay the same as it ages. While kittens often have bright blue eyes, their eye color can change dramatically by the time they reach adulthood due to melanin production. A cat’s final eye color is usually established by 8 weeks of age.
Another myth is that all black cats have yellow or green eyes. While this is often the case, black cats can also have brilliant copper, gold, or orange eyes. The specific eye color is determined by genetics.
There’s also a misconception that eye colors like green and hazel occur naturally in cats. In reality, these eye colors indicate the cat likely has some Siamese ancestry, as Siamese cats carry a gene mutation affecting melanin production which leads to light eye colors.
While cat eye colors can change slightly over time, dramatic shifts from blue to yellow or vice versa are not common. Gradual changes are usually due to factors like melanin production, not environmental factors or diet as some myths suggest.
Conclusion
In summary, a cat’s eye color can appear to change for several reasons. Kitten’s eyes often transition from blue to their adult color between 6-8 weeks as their eye development progresses. Environmental factors like lighting can make eyes seem different shades. Some health conditions may also alter eye color temporarily or permanently. Additionally, different cat breeds are predisposed to certain eye colors due to genetics. While it’s normal for subtle changes to occur, significant variations could signify an underlying issue and warrant a veterinary exam. Monitoring your cat’s eye health and appearance is important, as the eyes provide a window into overall wellbeing.
A cat’s eyes reveal a great deal about their health and emotions. While variations can occur naturally, abrupt shifts in eye color should be evaluated by a vet. With proper nutrition, environment and care, cat owners can support good eye health and appreciate the unique beauty of their cat’s eyes over a lifetime.
