Why do dogs have different coloured eyes?

Dog eye color can vary widely due to genetic factors. The primary genes related to eye color produce the pigment melanin. Dogs with a lot of melanin will typically have brown eyes, while those with less melanin may have lighter, amber eyes or even very light blue eyes. The specific color is a result of the way light interacts with the iris and the amount of melanin it contains.

Some dogs have different colored eyes, a condition known as heterochromia. This can be due to the distribution of melanin across the two eyes. There are three types of heterochromia:

1. Complete heterochromia: This occurs when one iris is a completely different color than the other. This is commonly seen in breeds like the Siberian Husky, Australian Shepherd, and Border Collie.

2. Sectoral heterochromia: This is when a segment or sector of the iris is a different color than the rest of the iris in the same eye. This can occur in many different breeds.

3. Central heterochromia: This is when the central (pupillary) zone of the iris is a different color than the mid-peripheral (ciliary) zone, around the pupil.

Heterochromia can be inherited (as it often is in Huskies and Australian Shepherds), or it can occur as a random genetic variation. Additionally, it can be caused by a condition called mosaicism, where an individual has cells that are genetically distinct.

Please note that sudden changes in a dog's eye color could indicate a health problem, such as uveitis, cataracts, glaucoma, or other eye diseases. If you notice any changes in your dog's eye color, you should consult a veterinarian immediately.