Why Aren't My Eyes Blue?

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What determines a person's eye colour?

Genetics play a important role. However, determining the combination of genes and chromosomes is very complicated and random mutations happen quite often.

The main factors that determines the colour of a person's eyes are:

• The amount of melanin (a dark pigment), which is determined by the number of melanocytes (cells that make the pigment) in the iris (coloured part of the eye)
• Presence of some other less common pigments in the iris
  
• Deposits of proteins in the iris
• All of these come together and affect the way light is scattered and absorbed at the front of the eye

For this reason darker-skinned people generally have darker coloured eyes and lighter-skinned people have lighter eyes.

FAQ:
Q: Is it possible for eyes to change colour?
A: Yes. But it would most likely happen early in life. Babies can be born with a low amount of melanocytes which slowly increases with age.

Q: Can I change my eye colour?
A: Yes, with contact lenses :-)

Q: Is it possible to have two different coloured eyes?
A: Yes. It's called heterochromia. Its also possible to have different parts of the same iris be different colours. This is partially genetic and partially the way the pigment is dispersed.

Q: Are there any medical implications to eye colour?
A: Yes. Lighter eyes tend to be at higher risk for Age-Related Macular Degeneration and ocular cancers. Likely due to some protective effects of pigment.

Q: Why do you keep spelling colour with the letter "U" in it?
A: Because I am a British Canadian.

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