Recent research shows that blue-eyed men prefer blue-eyed women. Thus it appears that, at least to some observers, eye colour is important.

But why do humans have different eye colours?

It mostly comes down to the amount and location of melanin (yes, the same substance which controls skin colour) in the human eye. Pale eyes such as blue, grey or green eyes contain little melanin, dark brown eyes more. Which eye colour you get is primarily determined from genetic variation based on the eye colour of your parents.

But does your eye colour influence how you see?

It turns out that it does. The darker the eyes, the more light is absorbed as light waves pass through the eye, and the less light is available to reflect within the eye. Light reflection (scatter) within the eye can cause susceptibility to glare (eg. sun or headlights) and to poor contrast discernment. Thus it seems that people with darker eyes may have better vision in high-glare situations – perhaps this makes them better night drivers, for example.

Eye colour may also affect your colour vision. Here it seems that lighter eyes may provide some advantages.

So it seems to me that blue-eyed people should really go for dark-eyed partners – this way one can pick the paint colours, and the other can drive home at night.

References

Coppens JE, Franssen L, van den Berg TJ (2006) Wavelength dependence of intraocular straylight Exp. Eye Res. 82(4):688-92

Coren S, Porac C (1978) Iris pigmentation and visual-geometric illusions Perception 7(4):473-7.

Dain SJ, Cassimaty VT, Psarakis DT (2004) Differences in FM100-Hue test performance related to iris colour may be due to pupil size as well as presumed amounts of macular pigmentation Clin. Exp. Optom. 87(4-5):322-5.

IJspeert JK, de Waard PW, van den Berg TJ, de Jong PT (1990) The intraocular straylight function in 129 healthy volunteers; dependence on angle, age and pigmentation Vision Res. 30(5):699-707.