It could be a number of things. The first thing that comes to mind is that you sucumb to a slow breathing pattern too quickly and starve your body of oxygen. That could cause, from what I know; you to see the streaks of light. Although if you aren't dizzy when this happens, it could just be an opening of your third eye. You're able to see the way you percieve energy in your mind in reality. Whether you percieve energy that way consciously in meditation or in your subconscience I don't know, cause you haven't told me. Hope this helps.
when I was about 17 I started doing meditation and practicing various forms os psychokinesis, mainly telekinesis. After about 4 months of this I started seeing streaks of light going across my pariphial vision on a hourly basis and strange shapes... I stopped my paranormal exersizes and they stopped... I thought I was just going strange but my friend in california reported the same thing... has this happened to anyone else?