It is widely believed that true purple eyes are a naturally occurring human eye color, but this perception is largely a misconception. While eyes can certainly appear violet under specific circumstances, there is no distinct purple pigment in human irises. The perceived violet hue is typically a result of light interaction with very low levels of existing pigments and other structures within the eye.
Understanding Eye Color
Human eye color is a complex trait determined primarily by the amount and type of melanin in the iris, the colored part of the eye. Melanin is a pigment also responsible for skin and hair color. There are two main types of melanin involved: eumelanin, which produces brown and black hues, and pheomelanin, which contributes to red and yellow tones. The concentration and distribution of these melanins within the iris’s stroma, its front layer, dictate the eye’s final color.
Beyond pigmentation, the physics of light scattering plays a significant role. This phenomenon, similar to Rayleigh scattering which makes the sky appear blue, occurs when light enters the eye and interacts with the collagen fibers in the iris’s stroma. In eyes with low melanin content, such as blue eyes, shorter wavelengths of light (blue and violet) are scattered more prominently and reflected outwards, creating the blue appearance. This explains why blue or green eyes do not contain blue or green pigment; their color is structural, arising from how light is scattered.
Brown eyes, the most common eye color globally, result from a high concentration of melanin that absorbs most light wavelengths. Green eyes involve a combination of low melanin, some yellowish pigment (lipochrome), and the blue scattering effect, which together produce a green appearance. The intricate interplay between melanin levels and light scattering creates the diverse spectrum of human eye colors.
The Reality of Violet Eyes
The perception of violet eyes arises from a specific combination of extremely low melanin levels and the visibility of underlying blood vessels. This unique interplay causes light to reflect off the reddish blood vessels at the back of the iris, which then mixes with scattered blue light from the stroma, creating a violet appearance.
This phenomenon is most commonly observed in individuals with severe forms of albinism, a genetic condition characterized by reduced or absent melanin production. In such cases, the iris lacks sufficient pigment to obscure the blood vessels, allowing their red hue to contribute to the overall perceived color. While some people with albinism may have blue or even brown eyes, the complete lack of pigment can lead to eyes appearing red or violet. Less than one percent of the global population has eyes that appear red or violet due to albinism.
What Makes Eyes Appear Violet
External factors can also influence how eye color is perceived, sometimes making blue or grey eyes appear more violet. Lighting conditions play a role, as the way light hits the eye can alter the reflection and scattering of light within the iris. For example, specific ambient lighting, the color of clothing worn, or certain makeup shades can enhance or change the perceived hue of the eyes. These factors can cause naturally deep blue eyes to take on a violet tint in certain light or photographs.
A well-known example is actress Elizabeth Taylor, whose eyes were famously described as violet. While her eyes were a deep blue, their specific and rare amount of melanin, combined with external conditions and possibly her distinct double eyelashes, made them appear violet under certain circumstances.