The news source, Medical News Today, explains that heterochromia of the eye is caused by differences in melanin concentration and distribution. Melanin is a pigment that gives color to eyes, hair, and skin. This condition can occur in both humans and animals. The term heterochromia originates from the Greek words héteros meaning different and chróma meaning color. Sectoral heterochromia, which Olive has, is a rare form of this condition. Even among all-white cats, which commonly have complete heterochromia or differently colored eyes, Olive's specific form of heterochromia is extremely rare. Unlike spotty or diffuse heterochromia, Olive's irises each contain a blue and yellow hemisphere making her unique.

Olive, the cat with unique eyes, has a fascinating genetic backstory behind her mesmerizing gaze. Typically, all kittens are born with blue eyes that disappear once they start producing melanin. However, some cats like Olive's friend Charlie sport blue eyes throughout their lives. While many white cats with blue eyes tend to be deaf, Olive has perfect hearing and vision. Despite her odd appearance, Olive is adored by her fans and is simply seen as a beautiful creature.