The colour of our eyes may predict our response to pain
Pain is known to be linked to many factors including gender; age; hair colour and so on and is likely to be governed genetically. For instance having red hair can mean an increased resistance to anaesthetics and and increased propensity to anxiety.
A recent study looking at pre and post partum women wanted to see if eye colour had a link to how these subjects responded to pain. The subjects included 24 dark eyed ( brown and hazel) people and 34 light eyed individuals(blue and green).
Those with dark eyes had increased levels of anxiety; sleep disturbance; pain on rest and with movement and an increased likelihood of depression.
This indicates a genetic control the molecular physiology of pain.
American Pain Society 33rd Annual Meeting