I found out and have used this technique for a long time. It’s a great way to prolong your dreams if you feel like you’re about to wake up and your vision becomes black / blinded.
I find that I become blinded first when waking up, then after a few secons I’m awake. If there are any DC’s around when you get blinded, tell them to start talking. Since hearing goes after sight, tell all DC’s to start talking, shouting, whatever, and keep talking yourself. After a few seconds my vision usually clears.
Try it next time you’re about to wake