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  • Writer's pictureSonja Boost




Let’s delve into the fascinating world of eye colours, exploring the science behind these captivating hues.


How rare are different eye colours?

Globally, brown eyes, in their varying shades, are by far the most frequent. Green, on the other hand, is among the world’s rarest eye hues.


These are the percentages of different eye colours in the population:

·         Brown: 79%

·         Blue: 8 – 10%

·         Hazel: 5%

·         Grey: 3%

·         Green: 2%

·         Red or violet: less than 1%

·         Heterochromia – partly or completely different-coloured eyes: 1%


The colour of the eyes depends on how much melanin the eyes contain. Melanin, the same pigment that determines skin and hair colour, is also responsible for different eye colours. Melanin helps protect the eye by absorbing light, including UV light, that hits the iris.


Melanin in the iris comes in two different types:

Eumelanin, which produces a deep chocolate brown colour

Pheomelanin, which produces colours ranging between amber, green, and hazel


The amount and distribution of melanin within the iris influences whether eyes appear brown, blue, green, or other shades.

Brown eyes have the highest concentration of melanin. It absorbs most of the light entering the eye, giving it a dark appearance. Blue eyes are basically the absence of melanin. There is not any actual blue pigment present, but like the sky and the ocean, blue irises get their colour from the way the light scatters around the iris, called Tyndall scattering. Eyes can be green if there is some melanin present but not enough to completely obscure all the Tyndall scattering, so there is a bit of blue appearance mixing with yellowish pigment.




The genetics of eye colour is complex. As many as 16 genes influence the amount of melanin inside the specialized cells of the iris. Tiny changes to any of these genes can lead to a different colour. This means that you cannot always predict a child’s eye colour based on how their parents’ eyes look. Blue-eyed parents will not necessarily produce blue-eyed children.

Age and Eye Colour Changes


Eye colour can change over time, especially during infancy. Sometimes babies are born with blue or grey eyes, which can darken as melanin accumulates in the iris over the first few years of life. Exposure to light can trigger melanin production.

In rare cases, adults may experience changes in eye colour due to hormonal changes, health conditions, or an eye injury.

Health Conditions 

Certain health conditions and genetic disorders can also influence eye colour:


Humans do not naturally have red or violet eyes. Occasionally, though, people with albinism can appear to have red or violet eyes in certain lights. This is a product of light hitting blood vessels at the back of the eye.


As eye pigmentation is important for vision, people with ocular albinism can have visual symptoms, such as:


  • Blurry vision

  • Reduced depth perception

  • Longsightedness or nearsightedness

  • Nystagmus – rapid, involuntary eye movements

  • Photophobia – light sensitivity

  • Problems with the macula, or centre of the retina

In heterchromia, the two eyes might have completely different colours from one another but this condition is uncommon.

Some people are born with heterochromia, in others an eye injury or health problem might cause it.



Are you interested in changing your eye colour with contact lenses?

It is important to consider both the aesthetic appeal and the potential impact on your eye health. Consulting your optometrist will ensure safe usage and optimal vision while achieving the desired cosmetic change.


Written by: Sonja Boost


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