The animal kingdom is full of creatures with quirky colored eyes: Great horned owls, for example, sport stunning golden eyes, while cats see through bright green, yellow, or even orange eyes. But have you ever wondered why humans don’t show such colorful eyes?
Actually, these amazing animal eye colors are not that different from those of people.
When people talk about eye color, we are actually referring to the color of the iris, a muscular ring (known as the sphincter) inside the eye. If the iris contains a lot of melanin or pigment, then the eye will appear brown. As the amount of melanin decreases, the color of the eyes appears hazel, green, or blue.
The orange hue is actually an amber. The golden color is a variation of brown and all the colorations are variations along a very common color line, from brown, to amber, hazelnut, from there to green and blue.
With a few exceptions, such as the red-eyed tree frog, red is generally not included in this color scale. It is a common misconception that albino individuals have red eyes. In reality, your irises do not have any pigment, because the gene that controls melanin production is completely turned off in albinism. Instead, the red color comes from the blood vessels that support the iris.
Eye color may appear to change when a person’s eyes are dilated or contracted. When an eye is dilated (that is, when the pupil is large so it can catch more light), the iris is compressed and may appear darker because the pigment is packed together in a smaller area.
In contrast, when the eye contracts, on a bright sunny day, for example, the pupil contracts and the iris grows in size. When this happens, the color of the iris may appear less intense, because the pigment is more widespread.
But regardless of whether an iris is dilated or constricted, we regret to say that it is highly unlikely that humans have the same eye colors as owls or cats.
