Removing rear-seat vanity mirrors

My rear-seat vanity mirrors are rattling/squeaking badly...especially with the sunroof shade at certain points in the open position.

I want to take out the mirrors and see if I can put something to help stop the noise. I cannot figure out how to remove the mirrors. There are small holes inside the housing (visible when you open the mirror), but I've tried to put a small-blade screwdriver in there to see if it is some sort of release, but nothing. I'm afraid to break the mirror housing.

Does anyone have any insight into how to remove them?

Thanks in advance.

TopherS