I suppose this might be relevant? Maybe not...just saying
"... In mammals the pineal body is not light-sensitive, but a neural connection remains between the eyes and the gland." (Encarta link)
So much for the 'third eye'!
The retinal ganglian cells form an input to the SCN (Suprachiasmatic nucleus) which is the circadian pacemaker. The pineral gland does this function in other species but not humans.