After a few minutes of trying to Google the Reticular Activating System, all I have done is to verify that I can spell it correctly. This is the section of the brain that determines if you are awake or asleep. The normal setting is to be asleep. When you are awake it is this section of the brain directing your attention to your environment. When you lose track of your environment and your situation and even your body, and you start to feel like you are floating, your senses start to shut down. You stop seeing and hearing and feeling the surface you are held against by gravity. This is going to sleep. The vision part doesn't tend to be alarming because your eyes are closed anyway. It just seems to get darker and the light coming in through your eyelids goes away. It is like falling into nice, warm relaxation. Then your body seems to drop away. That's just part of going to sleep if you are still alert enough to be aware of the process. I read about an e-book which suggested closing your eyes and watching through your closed eyelids as you relax. You will tend to see things. Don't get too involved with them at first. Just watch passively and let them catch your attention. It gives you something to do and it helps to take your attention off your environment and your body. Then your Reticular Activating System can take you off high alert and let you drift to sleep.