I've written before that I suspected that Sarah Palin's glasses are just glass, and have no real correction. I think she wears them to give herself a bit of gravitas. Our society tends to view attractive women only in the context of their looks. Most folks do not look at an attractive woman and think "I bet she's really smart." So, I can understand her wanting to be taken seriously.
Anyway, look at the image below. Notice especially in the red circle. You will see the straight and unbroken line of the earpiece on both sides of the lens, and through the lens. You'll see the same unbroken line of the side of her head on both sides of the edge of the lens. Look at anyone wearing glasses, and look through the lens. Any correction at all will cause at least some distortion when you look through them.
Even if there is some correction there, it is exceedingly small. Certainly small enough that she doesn't really need the glasses.
No big point here, just noting this.
Picture lifted from Talking Points Memo, credit wdcpix.com.