Naturally occurring purple eyes, as a distinct genetically inherited color, are not recognized in human biology. What might appear as “purple” is often a rare variation of blue or violet, or a visual effect under certain conditions. This is particularly noticeable in individuals with very low melanin levels. The perception of purple is typically a visual phenomenon, not due to actual purple pigment in the iris.
How Eye Color Forms
Human eye color is determined primarily by the amount and type of melanin in the iris, along with how light interacts with it. Melanin is the pigment responsible for the color of our eyes, skin, and hair. Two main types of melanin influence eye color: eumelanin, which produces brown and black hues, and pheomelanin, which contributes to red and yellow tones. Higher concentrations of eumelanin typically result in darker eyes.
Blue and green eyes do not contain blue or green pigments. Their appearance results from the scattering of light within the iris’s stroma, a phenomenon known as Rayleigh scattering. In eyes with low melanin content, shorter wavelengths of light (blue and violet) are scattered more, creating the perception of blue. Green eyes arise from a combination of low melanin and a yellowish pigment, which, when mixed with scattered blue light, creates a green appearance.
Understanding Rare Eye Colors
Rare eye colors include very light blue or “violet” eyes, which are a rare manifestation of blue eyes characterized by extremely low levels of melanin in the iris. In these instances, the light-scattering effect becomes more pronounced, contributing to their distinctive appearance.
Albinism, a genetic condition, significantly reduces or completely lacks melanin production in the body, including the eyes. In severe forms of oculocutaneous albinism, the profound absence of melanin in the iris allows the underlying blood vessels to become visible. This can cause the eyes to appear pink or red. A “violet” hue can sometimes be perceived when this visibility of blood vessels combines with the blue light scattering that occurs in the eye. While albinism is associated with these lighter eye colors, not everyone with albinism has red or violet eyes; many have blue, hazel, or brown eyes.
The Appearance of Purple Eyes
What might be perceived as “purple eyes” is almost exclusively a visual phenomenon, not a distinct, naturally occurring eye color with purple pigment. This perception arises most commonly in individuals with severe forms of albinism. In these cases, the extreme lack of melanin means the red blood vessels at the back of the eye are visible through the translucent iris. When this red hue from the blood vessels combines with the blue light scattered by the iris’s collagen fibers, a violet or purple appearance can be created.
The exact shade perceived can vary depending on factors like ambient light. Certain lighting conditions can enhance the perceived purple hue. There is no known genetic mechanism that produces actual purple pigment in human eyes. The rarity of eyes that appear violet or red due to albinism is very low, affecting less than 1% of the global population.