I think this is normal sleep onset hypnagogia, more properly said: phosphenes. Isnīt it ?

If you focus too much or too hard it disappears or becomes less intense, but as long as you stay aware and relaxed it comes again and again and can become more and more vivid. This can indeed be used as a WILD technique, which i sometimes do, although i never had direct dream entry ( mostly because of excitement ), but somehow it helps to achieve DILD or OBE after you fall asleep. I remember i started a post about this some time ago. A very interesting effect that can happen with this is the so called black hole effect, but it is also fun to just contemplate the void after the light forms disappear and before they return again once i got the feeling that i was in deep space, in the midst of the stars