My dd is 9. She just started this type of thing. Not sure if your son is doing the same thing or not. She looks at a bright light, the sun, or out the window. Then closes her eyes quick and gets that bright vision of what she was looking at, even though her eyes are closed. Does that make sense? She does that over and over a few times, then it becomes kind of like strobe lights. Try it. Look out the window or at a bright light. Close your eyes and see that brightness. Then open and close your eyes a few times, slowly. I have no idea why she started this, but she says she likes it. She is older than your son, so I don't know how much control your son may have over the blinking. We are telling our daughter not to do it. When she does it when you are talking to her, it makes her seem disinterested and disrespectful, even though she is not and IS still listening. She is going to the doc soon for a check up, so I am going to mention this to the doc. Again, I have no idea if your son is doing the same thing or not, just sharing what we are going through right now.
S.