Phosphenes

What is the name of those things you see when you close your eyes?
I think it's "phosphenes"
The reddish patterns, the little stripes and dots and blurry
Little lines you see floating around when you close your eyes
And no one really knows what they are, or what they're for
Sometimes they seem to be brought on by sound
Or random electrical or magnetic firing
Sometimes phosphenes are called "Prisoners Cinema"
Some kind of eternal, plotless, avant-garde animated movie

Or maybe they're just screensavers
Holding patterns that just sit there, so your brain won't fall asleep