The color of a person’s eyes is determined by genetics and the amount of melanin pigment in the iris. While most people have brown, blue, green, or hazel eyes, some individuals appear to have purple eyes. This unique eye color is often misunderstood and can have a variety of causes.
The Structure and Color of Eyes
Human eyes contain a colored structure called the iris which surrounds the pupil. The color of the iris depends on how much of the pigment melanin it contains. More melanin means a darker eye color. The two types of melanin are:
- Eumelanin: Produces brown/black pigment
- Pheomelanin: Produces red/yellow pigment
The combination and ratio of these two melanins determine eye color. Brown eyes contain a lot of eumelanin. Green and hazel eyes have moderate amounts of both melanins. Blue eyes have very little melanin overall. Since melanin pigment causes eyes to appear darker, less melanin results in lighter eye colors.
Causes of Purple-Looking Eyes
So how can eyes occasionally take on a violet or purple appearance? There are a few possible explanations:
Low Melanin and Light Scattering
Some people with blue/gray eyes or light green eyes may appear to have violet eyes under certain lighting conditions. Since their irises contain low levels of pigment, more light is able to pass through and reflect back. The combination of low melanin and scattering of light can produce a purple look.
Albinism
Albinism is a genetic disorder that reduces the amount of melanin pigment formed in the body. People with albinism often have very pale blue eyes due to the lack of melanin. The eyes may range from light blue to purple when light reflects off the back of the iris.
Bruising
In some cases, physical trauma to the eye can cause a purple appearance. A black eye caused by bruising around the eye can sometimes make the iris appear to be a purple-ish tone depending on the severity of the bruising.
Color Contacts
Wearing violet/purple color contact lenses is another way to make your eyes look purple. While colored contacts can make light eyes appear darker, they should be properly fitted by an eye doctor to avoid eye health issues.
Conditions Affecting Eye Pigmentation
Certain medical conditions can potentially lead to eyes taking on a violet coloration due to changes in melanin production. One example is ocular albinism, which impairs melanin formation in the eye area specifically. This can result in purple irises from light reflecting off the back of the eye.
Genetic Mutations
In extremely rare cases, a genetic mutation may cause someone’s eyes to actually contain violet pigment. One example is a mutation in the OCA2 gene which helps control melanin production. Most people with natural violet/purple eyes likely have a melanin pigment imbalance rather than true purple pigments.
Prevalence of Purple Eyes
The exact prevalence of purple eyes is unknown, but it is likely very rare. Estimates suggest that less than 1% of the global population has violet eye coloration. Regionally, higher rates of fairer eye colors increase the chances for purple eyes. But true purple pigment in the iris is extremely unusual.
Conclusion
While authentic purple eye color is quite rare, there are a number of different factors that can cause eyes to appear violet under certain conditions. This includes low melanin levels, lighting conditions, injuries, and medical conditions affecting pigment formation. So if someone’s eyes look mysteriously purple, it may be a trick of the light or a sign of an underlying eye issue.