Eye Colour: What’s It All About?

‘Blue eyes beautiful, Brown eyes Brandy Balls, Green Eyes Greedy guts.’

The above was a saying that I remember from childhood, and one that I made me really happy to be blue eyed, feeling sorry for my brown eyed sister. I always thought that the reason that blue eyes were considered beautiful was due to the fact that they were rarer than the other eye shades, but although this was true for brown eyes, green eyes are even rarer than the blue variety. Maybe as a child of the 1970’s it was linked to ABBA, and the gorgeous blue eyes of Agnetha, lined with the bluest of eye liner of course! But what really influences the colour of our eyes, is there any science in it, or is it pure luck?

What determines eye colour?

Firstly we need to correct the terminology here, because when we say ‘eye colour’, what we actually mean is iris colour. Our iris colour is determined by the amount of  the main pigment in the eye, which is melanin. Melanin is naturally dark brown in colour. This means that the more melanin in the iris, the darker the eye colour will be. People with brown eyes have a large amount of melanin in the iris, while people with blue/green eyes have much less of this pigment.

Evolution of Eye Colour

There is a theory that originally, all eyes were brown. We lived in warmer climates and, as Melanin acts as a natural sunblock, blocking UV light, this was important to our health and well being. People with lighter eye shades like blue, green and hazel have less melanin in their eyes, making them more sensitive to light and UV rays. It is estimated that around 70-80% of the World’s population still have brown eyes, but as we moved into places with cooler climates, the need for quite so much Melanin in the eyes was less, hence the propensity for blue eyes in areas like Iceland and Scandinavia, where so many of the population have that Nordic ‘blonde hair – blue eyes’ combination. This, however, is only a theory, one of many when it comes to eye colour.

Another theory, one mentioned by Thera Tears in a recent study, is that eye colour can also have an effect when it comes to SAD (seasonal affective disorder). They say:-

Seasonal Depression Theory: Blue-eyed people may have some protection against Seasonal Affective Disorder (SAD), a type of depression linked to lack of sunlight in winter. Lighter eyes are more sensitive to light, which might help melatonin and serotonin regulation in the body during darker months. 

Changes to eye colour

There can be changes to eye colour as we progress through our lives, and these can often be linked to health issues. For instance, a cloudiness to the lens of our eyes can be a sign of Cataracts, whilst Heterochromia, the rare condition where a person’s eyes are two different colours, can be caused by an eye injury, or an illness like Hirschsprung’s disease and neurofibromatosis 1. Any changes to our vision and eye colour needs to be looked into as early as possible, and medical attention should be sought, particularly if you are also diabetic.

What colour are your eyes?

Sharing is caring!