For the last three nights, I have had a strange occurance. After I stop reading and turn out the light, with my eyes closed, it starts getting darker. I open my eyes, the room is getting darker, and I see glittery bubbles rising. It only lasts for a minute, maybe less. Then everything looks normal again. That happened two nights in a row. Last night the room got darker again, but this time yellow shapes paraded in front of my vision ...from left to right, different sizes...again, it didn t last very long. Any ideas??