The purpose of this research study is to test whether researchers can reliably measure the response pupils have when an acute painful stimulus is experienced. Changes in the size of the pupil of the eye can be an indicator of brain activity in a region of the brain that is important for feeling pain.
Description: pupil diameter in response to 5 second presentation of noxious heat stimuliMeasure: Percentage of change in pupil diameter Time: 8 weeks
There is one SNP
Key secondary hypotheses: Compared to individuals homozygous for val at the val158met site of the catecholamine-O-methyltransferase (COMT) gene, those homozygous for met will show smaller pupil responses to noxious stimuli and weaker CPM. --- val158met ---