[QUOTE=adityananda;28913]
Simply observe these phenomenon, striving to be totally present in the moment of the experience, without attaching any value judgments to them based on your personal discrimination. In this way, all will be clear in due time!
[/QUOTE]
I am a somewhat regular meditator and less disciplined yoga practioner who has had sensations of varying degrees in the ajna chakra area for years and the above sounds like great advice to me. At first when this started a few years ago i thought that it really meant something special and wasted some time and energy feeling special and trying to find out what it meant and if there was something i should do about it. I still feel sensations in that area from time to time but not as intensely as i used to. I think the best thing is to relax, let go, be present and breathe 
EDIT: About the visual phenomena, some people see visual artifacts when experiencing alpha brain wave states. Alpha waves are perfectly normal when one is focused internally or entering sleep or meditating. The visual manifestations can be quite entertaining tho cant they
If you are seeing lights before sleep they could also be hypnagogic flashes (check google) alot of people get them before sleep overtakes.
Also i wanted to note that the above opinion is from the perspective of a buddhist meditator and not a yoga practioner. Sorry if it does not apply, forgive me, im a noob at yoga spirituality.